Attempted to recharge. Proper procedure and a question....

[nullset]

So I finished replacing the lines in 2072.

Background:

I'd been running with A/C quite happily for some time, then one day I hear "hissssss.....". By the time I get to my evacuate recharge station, I've lost all my R-12.

I got new lines, and a new accumulator, and a new condenser (see my 'oops' thread for that).

I drew a vacuum down below 29" (around 29.5" inHg, I believe).

I connected my A/C service machine and opened the high side valve and dispensed .5 pounds of R-12, as per the service manual, then closed that valve and jumpered the low pressure cutoff switch and started charging the low pressure side.

It got about 1.5 pounds more (2 pounds total, still half a pound shy of a full charge), and I noticed that the high pressure side was really high - around 250 psi. It also seemed to stop sucking more R-12 in. I then saw some white smoke come out of the compressor, and immediately shut everything down and started vacuuming the system again.

What happened? Did I do something wrong? Could there be a clog somewhere?

I did try turning the car off at some point and the pressures did equalize pretty quickly. At no point was cold air coming out of the system. It was rather warm, in fact. Could this be caused by a clog in the evaporator? I bought a new variable orifice tube and I think it was properly installed, though it wasn't perfectly 100% straight in the tube. It was pretty close, though. Maybe that tube got bent? At this point I'm willing to consider anything, but I'd strongly prefer not to replace the evaporator core.....

Advice is greatly appreciated. I'm assuming at this point that I at least damaged the compressor. I'm going to borrow one from the project car and replace it tomorrow, if everything else checks out.

--buddy

[Ron]

Were you were adding gas v/s liquid at the time?
Liquid can lock the compressor and smoke the clutch, and worse.

When you saw 250, what was the low side?
If it was particularly low, it could be a blockage.

What was the ambient temp at the time?
If 100F+ (like the rest of us today ;-), 250 is not really high, especially if you weren't using a box fan...

[nullset]

At some point I wanted to make sure my jumper wire was working, so I removed and reconnected it. That was when I saw the smoke, so I think that was the clutch smoking.

Is it most likely damaged at this point? How difficult is the clutch to replace, or should I get a full compressor rebuild kit? I'm lucky to have a project car with no pressure on the A/C that I can borrow parts from!

--buddy

[Ron]

OOPS...I sent your reply to the bit bucket...

IIRC, most machines will do gas only, but some do either. I'd guess gas if you have a single (divided) tank. Of coarse you can flip the tank on some, if you can get to it, to get liquid. But you should never have a need to and I doubt your machine would like it!

Did you try it after it it had a chance to settle.

You should ALWAYS add to the low side (gas). Trying to add to the high side will put too much pressure on whatever you are using to do it with and is dangerous. Some add liquid to speed things up, but using the service port right at the compressor is asking...no...begging for it (liquid of, any kind, will not compress).

I usually put in as much (gas) as it will take quickly (using my machine, or cans) then turn it on (MAX AIR).

The quicker you were at shutting it off, the better your chances are...and it could have been the belt smoke if you are lucky.


[EDIT]
You should shop around for the clutch and/or compressor. Note that prices can be 200% different from place to place for the same ones. And amazingly you can often find a complete unit with clutch for less than the clutch alone (they get to sell you freon and a warranty required accumulator ;-)

Don't just replace either w/o trying it again...I have seen people lock them up with liquid more than once and run it for years. See if you can determine which your machine was doing first...

[Bitsyncmaster]

If the VOV is bent, it will not work. That's why I went back to the standard orifice. You should not have to jumper the switch to charge.

[DMCMW Dave]

You should not have to jumper the switch to charge.

I agree - this is dangerous.

Very high high side + very low low side + no cold = plugged orifice tube. If the switch had not been jumped the compressor would have turned off before damaging itself. (250 is not all that high at the 90+ ambient, BTW)

Where did the smoke come from? Was it smoke or freon/oil?

[nullset]

I agree - this is dangerous.

Very high high side + very low low side + no cold = plugged orifice tube. If the switch had not been jumped the compressor would have turned off before damaging itself. (250 is not all that high at the 90+ ambient, BTW)

Where did the smoke come from? Was it smoke or freon/oil?

It was a puff of white smoke coming from the very front of the compressor. It really looked like the clutch.

The workshop manual says to jumper the low pressure switch while charging, which is why I did it. What's the proper procedure?

My car doesn't have a high pressure cutoff. At what point should I say "oops that's too high" and shut it down?

Today I'll grab a non variable orifice tube from my local parts house, and give that a try.

--buddy

[Bitsyncmaster]

As soon as you get the low side open to the can of freon, you get plenty of pressure to close the low cutout switch without a jumper. So start the engine, put your AC to Normal and fan to max and continue to charge. Small cans will need to be heated to keep the gas flowing. You should start to get cooling after about one lb of charge. I keep a thermometer in the center vent as I'm charging and when the temp peaks coldest, add a little more freon and call it charged.

Your high side pressure will run high because your fans are not moving enough air over the condenser. Sometimes AC shops will add a fan blowing over the front of the car. I would stop charging if the high side goes above 300 PSI.

[nullset]

As soon as you get the low side open to the can of freon, you get plenty of pressure to close the low cutout switch. So start the engine, put your AC to Normal and fan to max and continue to charge. Small cans will need to be heated to keep the gas flowing. You should start to get cooling after about one lb of charge. I keep a thermometer in the center vent as I'm charging and when the temp peaks coldest, add a little more freon and call it charged.

I'm not using cans, I'm using an A/C service machine.

That I didn't have cooling after 1.5 pounds to me indicates that there's something wrong. I'm going to replace the orifice tube with a new non-variable one and see if that works.

I'm also worried that I may have lost some R-12 in the process. Time to go craigslisting.....

--buddy

[David T]

Reasons for excessive high side pressure:
Over-charge of refrigerant
Air in the system
Plugged orifice
Fans not running to move air over the coils or coils blocked
Moisture in the system freezing and blocking high-to-low side

You really need to use a proper vacuum pump to get way lower than "inches" vacuum. You should also be pressure-testing your work before filling with refrigerant. Jumping the low pressure switch is not bad BUT. You MUST monitor the high and low sides constantly. Are you filling with a charging cylinder or a scale? How are you measuring the amount you are filling the system?
David Teitelbaum






I'm not using cans, I'm using an A/C service machine.

That I didn't have cooling after 1.5 pounds to me indicates that there's something wrong. I'm going to replace the orifice tube with a new non-variable one and see if that works.

I'm also worried that I may have lost some R-12 in the process. Time to go craigslisting.....

--buddy

[nullset]

Reasons for excessive high side pressure:
Over-charge of refrigerant
Air in the system
Plugged orifice
Fans not running to move air over the coils or coils blocked
Moisture in the system freezing and blocking high-to-low side

You really need to use a proper vacuum pump to get way lower than "inches" vacuum. You should also be pressure-testing your work before filling with refrigerant. Jumping the low pressure switch is not bad BUT. You MUST monitor the high and low sides constantly. Are you filling with a charging cylinder or a scale? How are you measuring the amount you are filling the system?
David Teitelbaum

I was at ~-29.5 inches mercury. That's a pretty damn deep vacuum, and is actually further than what most A/C shops can/will pull. An absolute vacuum in ~-29.92 inches mercury, for reference. I believe that's around 750 microns. The only gauge I have is my manifold set, which I believe to be accurate.

At >100 degress fahrenheit (which it was in the shop where I was working), I believe that is more than sufficient vacuum, and it held for several hours before I started charging.

My charging system has an indicator of how much has been dispensed.

I think the problem was the variable orifice tube, since the high side pressure did not seem to be changing during the charging, and there was no cooling. I'm certain that, prior to inserting the orifice tube, there was no clog.

--buddy

[David T]

The compound gauge on the manifold set is not accurate at all for low vacuums. You need an electronic gauge that reads in microns and you want to get to 700 at a minimum, 400 if you can (and should). Leak-testing by holding a vacuum is not a very good indicator, you are only using a differential of about 15 psi and if there is a leak you are pulling in air and moisture. To leak-test you pressurize with 200 psi Nitrogen and bubble test the connections. VOV's are prone to sticking especially if there is any moisture in the system. If you didn't get to at least 700 microns for an hour and replace the dryer you can figure you have moisture in the system and it froze the VOV. Just because many shops are sloppy is no reason for you to be if you are going to do your own A/C work. It takes an expensive investment in equipment or you find a GOOD shop that wants to do work that will last. All too often they get you going only to have you come back because they didn't want to take the time or the investment in equipment to do the job right. There is also the pressure of competition. If they won't do the job fast and cheap the customer will just take the car to a shop that will.
David Teitelbaum

[Ron]

An absolute vacuum in ~-29.92 inches mercury, for reference. I believe that's around 750 microns.
...
I think the problem was the variable orifice tube, since the high side pressure did not seem to be changing during the charging, and there was no cooling. I'm certain that, prior to inserting the orifice tube, there was no clog.

29.92 inches mercury == 0 microns
...
I think you may be on the right track with the orifice tube.

[nullset]

David,

Thanks for the advice. My digital vacuum pressure gauge will be here tomorrow.

I also picked up another 30 pounds of R-12. That's enough for one charge, right? ;)

And a new orifice tube. I should be good to go soon.

Everything but the compressor and the evaporator core is brand new. Since I think I might've damaged the compressor, I'm going to borrow one from my project car. It's been open for a while but it seems to be in good shape.

I'll crack the system just long enough to replace the orifice tube then immediately revacuum. Hopefully that'll be okay, as the accumulator is brand new and I vacuumed the system within minutes of opening it.

If my vacuum pump doesn't get down low enough, I may seek out a new/better one, but I believe it will. It's a fairly nice pump.

--buddy

[Bitsyncmaster]

Nulset, clear some of your PMs. You can not exceed 300 in both your inbox and sent box. I normaly clear so each has 100.

[nullset]

Nulset, clear some of your PMs. You can not exceed 300 in both your inbox and sent box. I normaly clear so each has 100.

Fixed!

[David T]

Fixed!
I would at least check the oil level in the compressor. If you go to the Sunden site there is a picture with the dimensions on how to make a dipstick and how to measure the oil charge. Unless you heard a lot of bad mechanical noises you probably did not hurt the compressor but if you made a lot of smoke from the clutch you might have to readjust the clearance or replace it. You remove shims to adjust the clearance. it's in the Workshop Manual. You should have enough -12 for another 12 tries! When you open the system you should always cap the open ends. The compressor is a pretty rugged part.
David Teitelbaum