Recharged A/C readings

[Spittybug]

Ambient: 90*
Original vent temp at idle: 70*
~1500 RPM readings: LOW: 15 HIGH: 200
I would get frequent cycling for 5 minutes or so at startup.

I put in 1 can of 12oz (let's pretend it's R-12 for the internet police to have something to do....)
Took it a while to suck all the vapor in (yes, very careful not to let liquid get sucked in)

New vent temp sitting at idle: 60*
~1500 RPM readings: LOW: 33 HIGH: 280
It would only cycle if I revved up way high.

When I checked the pressures with engine off, I had 78psi/90psi before and 65psi/75psi after which I found odd. I know they are supposed to be very close to one another. And why they would drop?

So, my question to the esteemed group would be why my vent temp isn't lower given these pressures. Could I possibly still need more???? The chart on N:09:01 of the manual shows that for a 90* ambient temperature that the high side should be 170-200 and the low side 25-32 and the vent temp 35-39. I believe this to be done at idle. In that case, my figures at idle are 230/42

I know that if the high side is too high, that would indicate a blocked orifice tube. I don't think I'm seeing that though, do you? This was sitting in the garage with a small extra fan blowing on the radiator along with the fans blowing. I will take it for a test drive and see if higher RPM will bring vent temp down. I know I've had them at 50* before in this kind of weather; however the book's data says it should get down below 40*.........

Hummmm.

[DMCMW Dave]

Are both fans running? Actually this seems pretty close to what I see with the car sitting still in a hot garage. Try it on the road at speed.

If the gauges don't match you may have a slightly plugged orifice tube, but even with that they should equalize over time. Gauge calibration could be an issue too, I find that they are sort of approximate after a few years of being banged around.

[Ron]

Ambient: 90*
Original vent temp at idle: 70*
~1500 RPM readings: LOW: 15 HIGH: 200
I would get frequent cycling for 5 minutes or so at startup.

I put in 1 can of 12oz (let's pretend it's R-12 for the internet police to have something to do....)
Took it a while to suck all the vapor in (yes, very careful not to let liquid get sucked in)

New vent temp sitting at idle: 60*
~1500 RPM readings: LOW: 33 HIGH: 280
It would only cycle if I revved up way high.

When I checked the pressures with engine off, I had 78psi/90psi before and 65psi/75psi after which I found odd. I know they are supposed to be very close to one another. And why they would drop?

So, my question to the esteemed group would be why my vent temp isn't lower given these pressures. Could I possibly still need more???? The chart on N:09:01 of the manual shows that for a 90* ambient temperature that the high side should be 170-200 and the low side 25-32 and the vent temp 35-39. I believe this to be done at idle. In that case, my figures at idle are 230/42

I know that if the high side is too high, that would indicate a blocked orifice tube. I don't think I'm seeing that though, do you? This was sitting in the garage with a small extra fan blowing on the radiator along with the fans blowing. I will take it for a test drive and see if higher RPM will bring vent temp down. I know I've had them at 50* before in this kind of weather; however the book's data says it should get down below 40*.........

Hummmm.
Check flap operation!

Measure ambient temp right in front of condenser.
(IF cooling system has nothing to do with the problem, check with engine just warmed up if you don't trust the extra fan).

Take readings when the clutch cycles out!

High/High => Overcharged, air, moisture (if cooling some, but I'm sure you evacuated it ;-), Condenser Air Flow/Radiator-cooling system.

Turn your internet off, read both sides, put the low adapter on the high side and read it as a gauge comparison check ;-)
You must do this when it is dead cold.

Why "they dropped"- Same reason as two equally sized cans where one is full and the other half full will have the same pressure, if allowed to sit together long enough ....the refrigerants were not the same temperature when measured.
Let it sit all night and if it is 70F in the morning, they WILL measure 70.2psi for R12 (71.2psi for 134a) -- Another way to check your gauges. See chart here (http://dmctalk.org/showthread.php?1244-Refrigerant-Temp-Pressure-Chart) for other refrigerants/temps.

Pollute a little bit, then turn your internet back on...:deviltail:

[Bitsyncmaster]

Why "they dropped"- Same reason as two equally sized cans where one is full and the other half full will have the same pressure, if allowed to sit together long enough ....the refrigerants were not the same temperature when measured.
Let it sit all night and if it is 70F in the morning, they WILL measure 70.2psi for R12 (71.2psi for 134a) -- Another way to check your gauges. See chart here (http://dmctalk.org/showthread.php?1244-Refrigerant-Temp-Pressure-Chart) for other refrigerants/temps.

+1

As Dave S said, try it when driving. If you still only get 60 deg., my first guess is your drain is plugged. Put in "Bills" drain change. When I did that my temps when way down. Second guess would be your condenser needs to be flushed.

[Ron]

To be clear, "High/High" means both sides high.

[David T]

To be clear, "High/High" means both sides high.

My guess is that you have air in the system and that is why your pressures are high and you are not getting cooling. One "trick" shops use is when they are working on a car in the and it is standing still you put a fan in front of it to get more air passing over the condenser to simulate the car moving a little. Look and see if you are "making water". If you aren't you aren't cooling enough and with those pressures it is because you have air and cannot get enough refrigerant in. Topping off can only work if the system never got low enough to let air get in.
David Teitelbaum

[Ron]

I agree on the basics you mentioned, but if I know Spitty, he originally vacuumed it to virtual zero, all night long, so if only one can gives him 280 psi, there is no way air or moisture could be in the system.

I'm sticking with flaps, or it was low on charge, but high now...maybe the plugged drain idea too. $.02

[Spittybug]

You don't know Spitty :mecry:

I have never "opened" the system since DMCH put it in back in 2007 or so. Degraded NOS parts or poor workmanship (they were having service department "issues" at the time), I've had to throw in about a can a year for the last 3 years. I therefore never bothered to evacuate it.

It makes plenty of water and the drain is free and clear.

How the heck do I check flap operation without disassembling things?

The HF gauges I use have two very different scales for high and low, so it is entirely possible that the static difference is due to +/- error on them.

I'm still going for a drive and check it, but if I determine I need to evacuate system and reload, then I'll need to go to someone that can capture, vacuum and reinsert..... ugh. I'm sure they'll pull the old "we are legally required to find the leak...." crap and next thing you know I'll be into $$$.

[Ron]

:slap:

Have you ever had to put more than two cans in at once? (The system pressure has to be lower than ambient to get air or moisture in it....). If not forget it , for now.

Bleed off the refrigerant until your high side cut off pressure matches the pressure listed for the ambient temp (in front of the condenser) found in the chart.

There is a test procedure for checking the flaps by ear in the WS manual (I think it was for AC and heat, not sure now, easy to find with the hybrid PDF..)

[Spittybug]

I do not recall ever having put more than 1 can. I never recall a reading as low as 14-15 (ambient, right?). So I don't *think* I have air in the system. I will look up door diagnostic. My high pressure switch should cut off the compressor if it gets too high at higher RPM, right?

[Ron]

" I never recall a reading as low as 14-15 (ambient, right?)" I'm not sure of what you are asking?
Yes it should cut it off no matter the RPM. But it will let it go a lot higher than it is ever supposed to run (Protection limit, not operation)

[kings1527]

" I never recall a reading as low as 14-15 (ambient, right?) I'm not sure of what you are asking?
Yes it should cut it off no matter the RPM. But it will let it go a lot higher than it is ever supposed to run (Protection limit, not operation)

I've read that the high-pressure relief will operate at 440 psi, so like Ron said, you have a long ways to go. And you know you're draining at the evaporator drain, so that's good.

Have you tried a 'feel test' at the evaporator? You can feel the evaporator inlet and outlet and both of them should feel the same temperature. But make sure when you're feeling the inlet that you're feeling it AFTER the orifice tube, past the dimples toward the firewall.

If the outlet is warmer, then you have a superheated condition. This would mean that the evaporator is picking up heat from the passenger compartment and sending it out the outlet. The most common cause of this is low refrigerant and you could test it by adding a 1/4 lb of refrigerant to see if it goes away and if it does, great, you've found the problem. If adding a 1/4 lb doesn't make it go away, then you might have an issue at the orifice tube or accumulator (somewhere 'upstream' from the evaporator).

If both of them feel the same, then at least you know the AC circuit is working correctly and there's something else wrong, like the temperature flap, vent connection, vacuum line, etc.

[Spittybug]

:nana2:

Cruising around neighborhood gets it down to ~50*, up on the highway it goes down a few more. Yeeha. Prize to Dave S. (so what else is new). It's high 80's here today (cool for Houston), so I'm guessing I'm getting about a 40-42* drop. I think that is probably as good as it gets.

Thanks for all the help.

[David T]

I do not recall ever having put more than 1 can. I never recall a reading as low as 14-15 (ambient, right?). So I don't *think* I have air in the system. I will look up door diagnostic. My high pressure switch should cut off the compressor if it gets too high at higher RPM, right?

It is possible to get air in if the low pressure switch is set too low (or not working) and the low side goes negative. When putting a gauge set on you also have to bleed out the air or you wind up pushing it in. Before hooking up you always check that your gauges are "zeroed".
David Teitelbaum