Low pressure switch - cutoff pressure for R134a

[82DMC12]

I just completed a 1,500+ mile round trip from Kansas City to Kentucky Bourbon Country. The car performed beautifully, which is confidence-inspiring after my frame off which I completed a year ago. Even in driving rain, no leaks - and that was the first time my car saw rain in over 10 years!

The only issue I had (aside from a wiper blade malfunction) was I found on an overcast day in rain (humid, so needed the AC on but low outside ambient temp) my A/C would gradually have less air volume for a given fan speed. I assumed I was experiencing evaporator frost-up. When I parked at the destination, sure enough my accumulator had frost on it. On the drive back home (9 hours) even though it was hot out I had to turn the mode switch to Vent for about 10 minutes every two hours to defrost the evaporator and get my air speed back up. High ambient temp on the way home did not allow the accumulator to frost but you could tell it was frosting inside the HVAC box.

When I got home I put gauges on it and found my charge and operating pressures to be correct but the low pressure switch wasn't cutting out until about 15 PSI. Of course that would cause the compressor to cycle less often, if at all, given certain ambient temps and steady engine speed.

I have it adjusted now to 20 PSI which, so far, is working great and still giving 38F vent temps. I would have to take a long road trip to really test it again though.

Wondering if 20 PSI is sufficient or if I will continue to get freeze-up? I see 18-21 PSI is "normal" for R134a but one vendor on a different post mentioned 25 PSI which I think would result in short cycling on all but the hottest days.

[JBaker4981]

Following.

Ironically enough, my car is doing the same thing from the same trip. Still have not followed your advice as I've not even LOOKED at the car since I unloaded it on Sunday... but I'm going to tackle this before Friday night if I am going to an AACA car show on Saturday :)

I can let you know of the behaviors after the adjustment

[82DMC12]

I haven't heard anything from anyone else regarding this topic, but so far so good at 20 PSI cutoff. Air conditioning is working very well and no signs of freeze-up since adjusting the switch. I haven't been on another long trip yet but maybe I'll go on a weekend afternoon highway cruise to give it another test. Another plug for ceramic tint, too - the cabin cools down a lot faster and stays comfortable, so nice that I usually only have the A/C on fan speed 1 or 2 once the cabin has cooled, and even then, the blend knob only around 2 o'clock. My A/C is highly effective!

[dmcman73]

I haven't heard anything from anyone else regarding this topic, but so far so good at 20 PSI cutoff. Air conditioning is working very well and no signs of freeze-up since adjusting the switch. I haven't been on another long trip yet but maybe I'll go on a weekend afternoon highway cruise to give it another test. Another plug for ceramic tint, too - the cabin cools down a lot faster and stays comfortable, so nice that I usually only have the A/C on fan speed 1 or 2 once the cabin has cooled, and even then, the blend knob only around 2 o'clock. My A/C is highly effective!

I have mine set to about 20-21PSI as well, haven't had any issues and the A/C works really well.

[Ethan Rode]

Four Seasons 36674, or NAPA 207883 is a direct replacement for the original switch, but is calibrated for R134a

[82DMC12]

Four Seasons 36674, or NAPA 207883 is a direct replacement for the original switch, but is calibrated for R134aDo you happen to know exactly what the cutoff pressure is?

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[David T]

The best way to set up for -134 is to measure the correct amount into the system. It is 10% less than the amount of R-12. Then you set the pressure switch to cycle the compressor with the motor at 1,000 RPM's and the fan set to high. This is assuming the evap coil and the condenser coil are nice and clean and you have a fan blowing at the front of the car while you do it (and it is not TOO hot) where you are doing it. It's all about temperature.

[Michael]

I just worked on my system and need to adjust my switch and this is good info. I believe I had it set to 25-26ish and it always worked well but if I can get away with 20, I'll try it.

[The_J]

Do you happen to know exactly what the cutoff pressure is?

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according to rockauto "off" is 25, and "on" is 49. Although rockauto also shows this switch fitting a 78-93 chevrolet, which makes me think its an r12 switch since r134a wasnt used (at least on chevy pickups) until 1994 models. However the pressures are in line with r134a.
on the subject, the delorean was originally filled with 2.7lbs of r12, then they later released a bulletin stating to reduce it to 2.2lbs of r12. A 1998 chevy pickup factory spec takes 2.0-2.2lbs of r134a, the condenser is larger compared to a delorean, but theres far less hose on the pickup, im convinced a delorean needs 2.0-2.2lbs of r134a, I certainly wouldnt run any less. Both the pickup and delorean use an accumulator, and a sanden style compressor. this is how i set up my car when i did the conversion and it seems to work great.

[82DMC12]

according to rockauto "off" is 25, and "on" is 49. Although rockauto also shows this switch fitting a 78-93 chevrolet, which makes me think its an r12 switch since r134a wasnt used (at least on chevy pickups) until 1994 models. However the pressures are in line with r134a.
on the subject, the delorean was originally filled with 2.7lbs of r12, then they later released a bulletin stating to reduce it to 2.2lbs of r12. A 1998 chevy pickup factory spec takes 2.0-2.2lbs of r134a, the condenser is larger compared to a delorean, but theres far less hose on the pickup, im convinced a delorean needs 2.0-2.2lbs of r134a, I certainly wouldnt run any less. Both the pickup and delorean use an accumulator, and a sanden style compressor. this is how i set up my car when i did the conversion and it seems to work great.Yeah but a Chevy truck doesn't have 20 feet of refrigerant lines going front to back each side.

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[Michael]

I put 2.1 of 134 in mine but then added about half a pound later on. I noticed the low side was a bit weak when adjusting my low pressure switch.

[David T]

I put 2.1 of 134 in mine but then added about half a pound later on. I noticed the low side was a bit weak when adjusting my low pressure switch.

Be careful. 2.1 lbs less 10% is 1.98 lbs. 2.1 lbs plus .5 = 2.6 lbs (Way too much, PERFECT!) R-134 runs a higher head pressures so you must reduce the amount of refrigerant to keep the head pressures from getting too high. Excessive head pressures and you will blow the relief valve and possibly hoses. Don't try to add -134 to get the same cooling capacity as you had with -12. The condenser coil is not sized large enough and the relief valve is set too low.

[Michael]

What should my vent temps be on a 90? day. I'm getting 55-60. Pressures look good although the high side is reading a bit low but still acceptable.

[82DMC12]

What should my vent temps be on a 90? day. I'm getting 55-60. Pressures look good although the high side is reading a bit low but still acceptable.


Hey GOAT!

Last week it was 89F in Kansas City on my way home from work. I actually had a vent temp thermometer and I was recording 38F after about 10 minutes of driving with R134A. I was able to maintain that temp while cruising about 40 MPH with vent speed on 2 or 3 and dial set to MAX AC. If I was slower than 40-ish or at a stop light, the vent temp went up to maybe 42F but then quickly went back down to high 30's once I was moving nicely again. Very comfortable and even better with my recent install of ceramic tint.

This is with a Sanden 7 piston compressor (SD7H15), DPI hose kit, generic parallel flow condenser, stock evaporator, new accumulator and white orifice tube. I still have the low pressure switch cutting out around 21 PSI.

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[Michael]

Wow...definitely have a problem here. My AC has been jacked up ever since they punctured my low side line at a garage when doing a complete cooling hose change.

Long story.

Maybe I'll post a vid tonight of the gauges during compressor operation and compressor cut out

[Michael]

I ordered a ac recovery machine. I'm tired of taking my car to Neanderthals just because I don't have the proper equipment. I'm going to pull it down, put 2.1 in and go from there.

[82DMC12]

I ordered a ac recovery machine. I'm tired of taking my car to Neanderthals just because I don't have the proper equipment. I'm going to pull it down, put 2.1 in and go from there.Good move, for the cost of one trip to a shop to get my air conditioning vacuumed and recharged, I was able to buy all of the equipment I needed to do it myself. You'll be glad to be able to pull your own vacuum and confirm it is holding for a long time like overnight before recharging. And then if you find something is screwed up you can fix it yourself without having to pay for a repeat trip to the shop.

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[David T]

Good move, for the cost of one trip to a shop to get my air conditioning vacuumed and recharged, I was able to buy all of the equipment I needed to do it myself. You'll be glad to be able to pull your own vacuum and confirm it is holding for a long time like overnight before recharging. And then if you find something is screwed up you can fix it yourself without having to pay for a repeat trip to the shop.

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Leak testing by holding a vacuum is no test. It is only 15 psi negative and just sucks contamination into the system. It won't tell you where the leak is or how big it is. The only good way to test for leaks is with Nitrogen at no less than 100 psi and check the system with bubbles. You can buy used A/C equipment and it doesn't cost a fortune. Your problem will be getting the gasses. You can get a certification on line for a few $$$. Just learn how to handle high pressure gasses safely and use proper safety equipment. You will need the following;
A manifold gauge set with hoses
A GOOD vacuum pump and a bottle of vacuum oil (an electronic vacuum gauge is a very nice thing to have)
A recovery system w/ tank and extra filters/dryers
Tools to remove the service valve cores while under pressure
A spray bottle of "bubbles".
A tank of R-134
A tank of Nitrogen w/ regulator
A bottle of oil compatible with the refrigerant you are using
The rest of the tools you need are just wrenches you probably already have.
A Delta T of 20 degrees is all you need to get. You measure that by subtracting the temp of the air coming out of the vents from the temp in the cabin NOT the ambient temperature outside the car. If you see air coming out of the vents in the 30's you are probably overcooling and will freeze the evap coil. The compressor is not cycling enough.

[82DMC12]

I actually leak tested mine with nitrogen, I find not many DIY'ers are willing to do that. I did though. Requires an additional fitting for the yellow hose as well as a nitrogen regulator. The Amazon regulators are shit, I ended up getting a good one at a welding supply store.

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[Michael]

After much reading, I think I may have a bad/clogged orifice tube but I will have to evacuate and put the correct amount of freon in before diagnosing.

Actually, as cheap as they are, and it's suspect, would it not be a bad idea to just replace it while my system is empty?

[82DMC12]

After much reading, I think I may have a bad/clogged orifice tube but I will have to evacuate and put the correct amount of freon in before diagnosing.

Actually, as cheap as they are, and it's suspect, would it not be a bad idea to just replace it while my system is empty?

You're right, they are only a couple bucks. Has it ever been replaced, do you think? There is some risk of damage to the evaporator pipe which is resides in if it is hard to remove. If the pipe is straight and it's been out before, you should be able to get it out with needle nose pliers however there is a special tool you can buy that might make it easier and safer. Installing the tube can be difficult as well, you might have to make a tool out of copper pipe to push it far enough into the evap pipe. I posted a picture of the tool I made elsewhere, I can post it if you need to see it.

I'd say if you still have trouble after recharging, yeah, evac again and replace the orifice tube and the accumulator.

[David T]

You're right, they are only a couple bucks. Has it ever been replaced, do you think? There is some risk of damage to the evaporator pipe which is resides in if it is hard to remove. If the pipe is straight and it's been out before, you should be able to get it out with needle nose pliers however there is a special tool you can buy that might make it easier and safer. Installing the tube can be difficult as well, you might have to make a tool out of copper pipe to push it far enough into the evap pipe. I posted a picture of the tool I made elsewhere, I can post it if you need to see it.

I'd say if you still have trouble after recharging, yeah, evac again and replace the orifice tube and the accumulator.

Check if your high side pressure is too high and your low side pressure is too low. That would indicate a plugged (or partially plugged) orifice tube. Rare but possible. Look inside the hoses and pipes. If they are nice and clean and shiny it is doubtful the tube is plugged up. High risk of damaging that pipe. It is soft aluminum and you puncture it before you even know it. Too high a risk to "just replace it". Once you damage that pipe you have to disassemble the whole dash to R & R that evap coil. Big job! Better to not do it proactively. The orifice tube was put in and then that pipe was bent. Just trying to straighten it out can damage it and you can't remove the orifice tube unless you first get that pipe straight. "Good Practice" is to replace the dryer/accumulator during service and the cores of the service ports. I also use brass caps instead of the plastic dust covers for the service ports. If you do convert to -134 you are supposed to have a label indicating that and the amount. You should also install adapters for -134 over the service ports. Also a good idea to record the temps and pressures for future reference.

[Michael]

If I remember correctly, both high and low sides were reading lower than I wanted to see for the ambient temp. I then added 1/2 lb and saw pressures up but no discernable cooling improvement.

I guess I will just pull it down and put the correct amount and go through the tech manual diagnostic flow chart.

[Michael]

Pulling down now. Should I go with 2.0 lbs? The manual states 2.2 of R 12 so minus 10% would be 2 even.

[82DMC12]

I can't remember exactly how much I put into my car but I was just talking to another owner who did a r134a recharge and he used about 1.75 lb, going off of some kind of a generic R12 to 134a conversion chart. Also assuming 2.2 lb R12 is the correct charge.

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[Michael]

The manual does say 2.2. I may split the difference and go with 1.9.

Also, I think my mixing flap wasn't fully closing. I got under there while it was drawing down and I think I was able to get a little more throw out of the arm after loosening the rod keep.

[82DMC12]

Let me also point out that the little cans of refrigerant you get at the parts store are usually only 12 oz cans, not a 16 oz can. Just so you are sure you have enough on hand and get an accurate calculation.

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[Michael]

I'm using a recovery machine. Still in the middle of a leak test before I charge.

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[Michael]

Ok...after adding 1.9 lbs of 134a my pressures are:

Engaged at idle ambient at 90 degrees . No extra air over condenser

L 55
H 200

I had to adjust the low pressure switch because I couldn't get it to draw down to 22. Clutch disengaged...same ambient conditions. I did drive it home before these readings and I could hear the compressor cycling so I assume the lack of airflow over the condenser made the difference.

L peaks at 65
H peaks at 200

Obviously the low side is too high. I'm really leaning towards the expansion tube.

[82DMC12]

Take a look at this chart, it shows what the normal operating pressures should be at a certain ambient temp.

If you are in the sun with doors open, AC on, and the ambient temp is 90F, you should see AT IDLE low pressure about 45-55 PSI and high pressure at 250 - 270 PSI. If you open the throttle a bit like to 1800 or 2000 RPM , you should see the high side go up a bit while the low side continuously drops, and the compressor should stop at 22 PSI (as you have the low pressure switch set). Then you see low pressure rise, high pressure fall, and when the low pressure hits 40's again the compressor re-engages.

What exactly do you see when you do this?

Stick a thermometer in the dash vent and see what the vent temps are. You should also feel the low side metal fitting on the compressor be refrigerator-cold and sweating while the high side fitting is too damn hot to touch more than a moment.

The accumulator should also be cold and damp but not frosty.

You should also have condensation dripping out of the hose behind the accumulator after a few minutes of running the AC.

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[Michael]

I was going off the tech manual pressures but now I realize that is for r12.

Both high and low side pressures drop during throttle, when the compressor cuts out both rise to 65 and 200 before the compressor re engages..

I checked and all the pipes that are supposed to be hot, warm, cold are just that.

[82DMC12]

I was going off the tech manual pressures but now I realize that is for r12.

Both high and low side pressures drop during throttle, when the compressor cuts out both rise to 65 and 200 before the compressor re engages..

I checked and all the pipes that are supposed to be hot, warm, cold are just that.


When you open the throttle, the high pressure is supposed to go up while the low pressure drops (assuming the compressor is engaged and running). I'm not sure I can explain why the high pressure would also drop. Can you confirm that the adapter valves for your recovery system's hoses AT THE COMPRESSOR are both open and the "fill valves" for the gauges on the recovery unit are both CLOSED while monitoring the pressures? If both are fill valves are open, or leaking internally, you would probably see some mingling of the high and low side within the recovery unit itself. Just spit-balling here since I haven't seen high side drop when giving throttle before.

[82DMC12]

By the way, when the car is shut off and the A/C system cools back down to ambient temp, the high and low will equalize and you can check the gauge's temperature scale to see if the system is relatively close to being charged correctly.

See the photos below (this is my car with engine cold and the ambient temp was about 80F, compressor service valve knobs open, valves on gauges CLOSED), you'll see the inside scales of the gauges show various refrigerants including R134a. If the gauges are hooked up to the service ports and the engine is cold , the needles should both point to the same PRESSURE on both high and low AND the needles will point to approximately the current ambient temperature.

So, if it is 80F outside and the system is "cold", both needles will point to approximately 90 PSI because that is the pressure that corresponds to 80 F on the inner R134a scale.

It's not an exact science but a good ballpark reading so you know if you are way off. If the system is undercharged, both gauges will LOW and if the system is overcharged both will read high.

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[Michael]

I know the fill ports were closed...otherwise I would know real quick but my compressor adaptors are known to loosen while in use...I should have double checked to make sure they were still engaging the valve.

I will crank it cold tomorrow morning or evening and double check my readings.

[Bitsyncmaster]

By the way, when the car is shut off and the A/C system cools back down to ambient temp, the high and low will equalize and you can check the gauge's temperature scale to see if the system is relatively close to being charged correctly.

See the photos below (this is my car with engine cold and the ambient temp was about 80F, compressor service valve knobs open, valves on gauges CLOSED), you'll see the inside scales of the gauges show various refrigerants including R134a. If the gauges are hooked up to the service ports and the engine is cold , the needles should both point to the same PRESSURE on both high and low AND the needles will point to approximately the current ambient temperature.

So, if it is 80F outside and the system is "cold", both needles will point to approximately 90 PSI because that is the pressure that corresponds to 80 F on the inner R134a scale.

It's not an exact science but a good ballpark reading so you know if you are way off. If the system is undercharged, both gauges will LOW and if the system is overcharged both will read high.

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70702

Static pressure does not show a full charge. If you have one drop of liquid coolant it will show the same static pressure if you have 2 lbs of liquid.

[82DMC12]

Static pressure does not show a full charge. If you have one drop of liquid coolant it will show the same static pressure if you have 2 lbs of liquid.That's why I said it's a reference point only. It remains true that in general, if both gauges read low, the system is undercharged. In general, if both gauges read high, the system is overcharged. That would be one clue along with other points of evidence to make a diagnosis.

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[Michael]

I know I have the right charge. What I will do is tomorrow evening, I will make a quick video of the gauges. I was thinking the high side dropped with acceleration but on another video I took (before I confirmed my freon charge), it barely moved.

[Michael]

...then again, I think that was one of those tines when my valve knob backed off.

[DMC-Ron]

Static pressure does not show a full charge. If you have one drop of liquid coolant it will show the same static pressure if you have 2 lbs of liquid.



That's why I said it's a reference point only. It remains true that in general, if both gauges read low, the system is undercharged. In general, if both gauges read high, the system is overcharged. That would be one clue along with other points of evidence to make a diagnosis.

Dave is correct. The static pressure does not indicate the level of charge. You could have 1oz or 2lbs of refrigerant and the pressure indication would be identical. In an extreme case, if your gauges read a static pressure below ambient temperature then you have lost your charge and don't have any liquid refrigerant left. There would be no way to have the system static pressure read higher than ambient temperature.

Ron

[82DMC12]

All right, sounds like I have a misunderstanding of the static pressure. I sometimes have to work with equipment that has industrial HVAC built into it and while I do not do repairs, I sometimes have to give a rough diagnosis of why it's not working. The distributors of the equipment have explained to me that if a machine is found with both gauges reading surprisingly low, when the machine is not running, it is "almost surely" low on refrigerant. Same goes for both gauges reading high (over charged). Typically I would only be seeing these machines in an ambient temperature of 60 to 90 F , and I see a hell of a lot of them. If I see four in a row and three of them are all reading the same and the fourth one the gauges are low, I guarantee you the machine is not working right.

Maybe that does not translate over to automotive very well.

That being said, has anyone tried to charge the system using the superheat method? Since some of us are using different compressors and different types and sizes of condensers along with different types of fans, it seems like the optimal way to charge the system is not necessarily by weight but by hitting the optimal superheat change at the evaporator. You would need temperature probes to do this.

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[Bitsyncmaster]

All right, sounds like I have a misunderstanding of the static pressure. I sometimes have to work with equipment that has industrial HVAC built into it and while I do not do repairs, I sometimes have to give a rough diagnosis of why it's not working. The distributors of the equipment have explained to me that if a machine is found with both gauges reading surprisingly low, when the machine is not running, it is "almost surely" low on refrigerant. Same goes for both gauges reading high (over charged). Typically I would only be seeing these machines in an ambient temperature of 60 to 90 F , and I see a hell of a lot of them. If I see four in a row and three of them are all reading the same and the fourth one the gauges are low, I guarantee you the machine is not working right.

Maybe that does not translate over to automotive very well.

That being said, has anyone tried to charge the system using the superheat method? Since some of us are using different compressors and different types and sizes of condensers along with different types of fans, it seems like the optimal way to charge the system is not necessarily by weight but by hitting the optimal superheat change at the evaporator. You would need temperature probes to do this.

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If it reads low static then yes your almost completely out of coolant. You would have to have complete filled with liquid coolant to read high. So even twice the normal charge you would never see it read high.

[Michael]

OK, here is a video I just made. About 85 degrees, no airflow over the condenser other than the OE fans. I know the low pressure cuts out a bit early but I had to raise the threshold because it would never draw down to 22 lbs yesterday...looks like it would today but anyway It should still give you an idea of what my system is doing. Vent temps are 60- 65 ish

https://youtu.be/pbTAb8ay0Ls?feature=shared

[Michael]

I can only assume my pressures are normal and my expansion tube is blocked. My vent temps are just not where they need to be


https://www.youtube.com/watch?v=pbTAb8ay0Ls

[Bitsyncmaster]

I can only assume my pressures are normal and my expansion tube is blocked. My vent temps are just not where they need to be


https://www.youtube.com/watch?v=pbTAb8ay0Ls

Take it for a drive with a temp gauge in the vent. It may be your just not moving enough air through the condenser parked.

[Michael]

Take it for a drive with a temp gauge in the vent. It may be your just not moving enough air through the condenser parked.

Pretty much 60 all the time with maybe a dip to 55 degrees if I'm driving. I am not uncomfortable, I'm just a perfectionist and I want it to work right.

Does my high side look a bit low considering it's 80-90 degrees and no air circulation over the condenser? I know it's in range but maybe if the oriface tube is particularly clogged, that would be why my high side is lower at the manifold?

[82DMC12]

Pretty much 60 all the time with maybe a dip to 55 degrees if I'm driving. I am not uncomfortable, I'm just a perfectionist and I want it to work right.

Does my high side look a bit low considering it's 80-90 degrees and no air circulation over the condenser? I know it's in range but maybe if the oriface tube is particularly clogged, that would be why my high side is lower at the manifold?My understanding is the high side would be surprisingly high and the low side would be surprisingly low if the orifice is clogged. Think of it as a brick wall not allowing hot liquid refrigerant to pass through it. That would cause the high pressure to go up.

Is your accumulator cold and damp? Is it frosting? Is the evaporator core draining down to the ground? If it's mostly full of water you will get pretty crappy cooling.

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[Michael]

Accumulator is cold and wet, albeit cool would be a better term.

My car has never drained much condensate. I checked to make sure the drain port was clear, even took the boot and tube off so it would be sure to drain (I didn't care if it got on the frame or not). It could be that the water is just running down the underbody and frame and not much makes it to the ground. It does have a few drops of water under the fldrain, just not much.

[82DMC12]

Do you have a camera on a wire? Maybe good idea to remove your fan and see if you can get a look at the evaporator. On a hot day my car looks like its water broke there is so much humidity being removed through the evaporator drain. Of course that could also be because my evaporator sounds like it is 30? colder than yours.

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[Bitsyncmaster]

Nothing looks bad with the pressures (maybe the high side is a little low). Did you do a good flush of the system when you converted to R-134?

[Michael]

Do you have a camera on a wire? Maybe good idea to remove your fan and see if you can get a look at the evaporator. On a hot day my car looks like its water broke there is so much humidity being removed through the evaporator drain. Of course that could also be because my evaporator sounds like it is 30? colder than yours.

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My neighbor has a camera I can use. Good idea.

[Ron]

My understanding is the high side would be surprisingly high and the low side would be surprisingly low if the orifice is clogged.
...
The low side would go negative, I.E., show vacuum.

[82DMC12]

The low side would go negative, I.E., show vacuum.So it sounds like that's probably not it.

I still like my idea of a partially obstructed evaporator. Or there is something going on with the vacuum flap actuators and outside air or heater air is being mixed with the cold air.

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[Michael]

So it sounds like that's probably not it.

I still like my idea of a partially obstructed evaporator. Or there is something going on with the vacuum flap actuators and outside air or heater air is being mixed with the cold air.

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Unless there is a major break, I'm sure the heater flap is closing as I can hear it smack shut.

I'm going to borrow my neighbor's borescope camera and take a look at the evaporator area and see if maybe there is some blockage...I can't imagine it's got standing water in it as I would have surely smelled it by now.

The only other idea I have is maybe the expansion tube is missing altogether.

[82DMC12]

Unless there is a major break, I'm sure the heater flap is closing as I can hear it smack shut.

I'm going to borrow my neighbor's borescope camera and take a look at the evaporator area and see if maybe there is some blockage...I can't imagine it's got standing water in it as I would have surely smelled it by now.

The only other idea I have is maybe the expansion tube is missing altogether.If the expansion tube were missing, you would not feel any cold temp on the return side of the compressor. Everything would be hot , the gauges would equalize, and the compressor would be knocking from taking on hot liquid refrigerant.

Maybe leaves, etc packed up inside the evap box.

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[Michael]

That's good to know! Nothing would make me happier than to see a bunch of leaves or some stray piece blocking the evaporator fins. Maybe I'll tackle that tomorrow afternoon.

[dmcman73]

That's good to know! Nothing would make me happier than to see a bunch of leaves or some stray piece blocking the evaporator fins. Maybe I'll tackle that tomorrow afternoon.

If it does turn out to be leaves and/or other debris in there, when I finished rebuilding my HVAC box, I installed a 16X16 stainless steel wire cloth over the air intake under the cowl to keep all of that out. I just cut it to size to fit over the rectangular opening and just laid it over it, the cowl holds it in place once you re-install it. If you want, you could add a few dabs of RTV to hold in in place as well. This is what I used: https://www.mcmaster.com/85385T65/

[82DMC12]

If it does turn out to be leaves and/or other debris in there, when I finished rebuilding my HVAC box, I installed a 16X16 stainless steel wire cloth over the air intake under the cowl to keep all of that out. I just cut it to size to fit over the rectangular opening and just laid it over it, the cowl holds it in place once you re-install it. If you want, you could add a few dabs of RTV to hold in in place as well. This is what I used: https://www.mcmaster.com/85385T65/I did the same thing. I removed my cowl to replace it, and found a surprising amount of pine needles, leaves, dirt etc down there. I put that screen someone was selling under my cowl , same thing just has some edge trim on it to make it look pretty.

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[dmcman73]

I did the same thing. I removed my cowl to replace it, and found a surprising amount of pine needles, leaves, dirt etc down there. I put that screen someone was selling under my cowl , same thing just has some edge trim on it to make it look pretty.

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I made my own and made it with the edge trim, but found that the edge trim put pressure on the cowl and it also blocked water from draining so I removed it. Once the wire cloth is laid out and the cowl installed, it holds it nicely and you can't even see the edges of it (as long as you cut it where it isn't too wide and it it sticks out from under it).