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Ac quit after a 30 minute stop.  Pages: 12

Frank72785 on Fri July 11, 2014 3:07 PM User is offline

Year: 95
Make: Chevy
Model: Camaro
Engine Size: 355
Refrigerant Type: R134
Ambient Temp: 90
Pressure Low: 200ish
Pressure High: 150
Country of Origin: United States

Background. I replaced the clutch last year on this unit and it has been perfectly fine since. So on my adventures the other day i get back to my car after being in a store and the ac doesn't turn on.

Troubleshooting so far
Checked pressures. As listed above.
Checked the signal to the clutch. It's not there so that seems like the issue. Reason the car is telling the ac no I'm not sure yet. Checked swapped relays and fuses to rule them out.
The car has the 3 wire pressure sensor. I'm thinking somehow the pressure sensor is thinking it's way too much pressure and restricting it from engaging the clutch. It's been filled for about 14 months now so not sure why now it's a issue.
Any ideas?

Frank72785 on Fri July 11, 2014 3:13 PM User is offline

Pressures were measured with the compressor not engaged since it will not.

GM Tech on Fri July 11, 2014 5:39 PM User is offline

Most likely scenario-- 14 months is a long time- system refrigerant charge has dwindled- to point of rapid cycling- ECM (on F bodies) counts cycles and determines system is low on charge and sets a code 46 that disables the compressor engagement- to save it from burning up..

Reset code 46 with Tech I scan tool - or unhook battery for 10 seconds- and see if compressor engages- then recover charge and find and fix leak evacuate and charge to factory spec- and be cool....

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Frank72785 on Fri July 11, 2014 5:51 PM User is offline

Sounds good to me. Only thing that could make me think that it could be something else is that I've just had pcm retuned and recently have had the battery disconnected within the last 300 miles

Frank72785 on Fri July 11, 2014 7:44 PM User is offline

Alright ran over to a shop got it drained came home vacuumed it down for 35 minutes while I went and got some juice for it. Found mixed reports on 1.5lbs or 2lbs of refrigerant so I put 1.5 in ac worked great and did for the first 5 minutes of driving. Seemed like it would only work at very low rpms. So I added the last half of lb and went driving seems like it is still only working at basically idle. Popped the hood and at idle it kicks in and cycles like it should second I bkip the throttle it kicks off.

Frank72785 on Sun July 13, 2014 4:16 PM User is offline

Anyone have any ideas? Checked the pressure today while running I had 90psi on low end and 250 on the high. I bled the low end to the correct 35-40 and it ran well for 5 minutes then started its fluctuation stuff again you can smell the difference in the air its musty

webbch on Sun July 13, 2014 4:37 PM User is offlineView users profile

What are the pressures when it cycles off? I'm not familiar with this model exactly, but the evap temp sensor or the high pressure switch are 2 additional items that can cycle the compressor. If the PCM is getting erroneous inputs from either of these sensors, it can cause the situation you describe.

Not a fan of "bleeding off" the low side, because now you're back to an unknown charge level as well.

Frank72785 on Sun July 13, 2014 5:28 PM User is offline

Thanks for the reply. I'm starting to think maybe resetting the pcm again may solve some issues since the ac worked perfectly fine before the issue I had last week. And that was it just not turning on. So I did what was suggested emptied and filled back up and reset the pcm. And that's why I am where im at now.

I will get the readings on and off when I get back home tonight. In the mean time I'll reset the pcm and test it on the way home

Frank72785 on Sun July 13, 2014 6:46 PM User is offline

Quote
Originally posted by: webbch
What are the pressures when it cycles off? I'm not familiar with this model exactly, but the evap temp sensor or the high pressure switch are 2 additional items that can cycle the compressor. If the PCM is getting erroneous inputs from either of these sensors, it can cause the situation you describe.



Not a fan of "bleeding off" the low side, because now you're back to an unknown charge level as well.

Did what I said with the pcm and on the way home it worked for 20 minutes great nice and cool thought it was fixed but then I went up a hill about a mile from my house and that was it. Got home threw the gauges on real quick and the compressor was cycling 5 seconds on 10 seconds off. Off the psi would climb from 45 to about 80 once it hit 80 it would drop rapidly to 40-45ish once it hit that it would turn off again. High pressure stuck around 225 regardless if on or off. Went for a test drive after than and never seemed to give me cold air again. Even tried turning it completely off for 5 minutes. Nothing you can notice it engage based of the rpms. I'm lost on this issue.

wptski on Sun July 13, 2014 7:57 PM User is offline

The list at this site shows a 1995 Camaro, all engines hold 2lbs of R134A so you are undercharged. It's been stated numerous times here that the first step is to insure the proper charge.

Frank72785 on Sun July 13, 2014 8:40 PM User is offline

Quote
Originally posted by: wptski
The list at this site shows a 1995 Camaro, all engines hold 2lbs of R134A so you are undercharged. It's been stated numerous times here that the first step is to insure the proper charge.

Yes in my one comment I mentioned that I had initially put 1.5lbs in the guesstimated the last half of lb because it was a 12 ounce can. So I should have been close to 2lbs. But then my inexperience came in and I bled some out. Maybe the cheap cans that I bought weren't actually 12 ounces each? I generally try to not get the stop leak stuff which this didn't have stop leak in it.

Since my last post still troubleshooting I swapped my pressure sensor from my sunfire which is a known good sensor. Went driving again worked again for about 15-20 minutes then didn't for 10 then it came back for another 20 and I gave up for the night hoping it will work. Maybe I just need to vacuum it down again and start over?

mk378 on Sun July 13, 2014 9:24 PM User is offline

Works for a while then fails to engage suggests a clutch gap. Check if the compressor has voltage when it is supposed to be engaged but is not. Once you have the proper charge in you're done with that part. Low side should cycle off at about 25 and back on around 40. If it's a two wire switch on the low side you can just jump it and compressor should stay on constantly (leading eventually to evaporator freeze-up).

Situation is further complicated by the ECU software not being stock. Ask your tuner if the A/C is going to work any different from stock.

Frank72785 on Sun July 13, 2014 9:48 PM User is offline

Quote
Originally posted by: mk378
Works for a while then fails to engage suggests a clutch gap. Check if the compressor has voltage when it is supposed to be engaged but is not. Once you have the proper charge in you're done with that part. Low side should cycle off at about 25 and back on around 40. If it's a two wire switch on the low side you can just jump it and compressor should stay on constantly (leading eventually to evaporator freeze-up).



Situation is further complicated by the ECU software not being stock. Ask your tuner if the A/C is going to work any different from stock.

I'll recheck the clutch gap if it's dry tomorrow. It's a 3 wire sensor. Do cars computers have to learn the pressure sensors like o2s? And the tune worked for the first
200 miles of the engine with ac great.
Thanks

mk378 on Sun July 13, 2014 10:22 PM User is offline

Actually is it a TXV system? Those should not cycle on pressure at all, it uses evaporator temperature instead. Pressure sensor would be on the high side.

Frank72785 on Sun July 13, 2014 11:01 PM User is offline

Quote
Originally posted by: mk378
Actually is it a TXV system? Those should not cycle on pressure at all, it uses evaporator temperature instead. Pressure sensor would be on the high side.

There is a temp sensor on the evap it's a pita to get to.

Frank72785 on Mon July 14, 2014 3:21 PM User is offline

So still stuck. All that's left I guess is the evap temp sensor and the pcm. All that it seems it could be now. It being odb1 makes getting the codes read near impossible

webbch on Mon July 14, 2014 6:04 PM User is offlineView users profile

Quote
Originally posted by: Frank72785
So still stuck. All that's left I guess is the evap temp sensor and the pcm. All that it seems it could be now. It being odb1 makes getting the codes read near impossible

Yes, still need to vacuum back down and re-charge to correct level. Additionally, I still see clutch gap or evap temp sensor as possibilities - didn't see where you ruled out clutch gap. Give it a light tap if you can do so safely when it cycles off to see if that gets it going.

As for the evap temp sensor, look at your wiring diagram to see if you can break into the connection at a more convenient to access location. I'm guessing it's a thermister of some sort, and the manual should have resistance specs to check. Knowing the characteristics of resistanc vs. temp, I'd expect you could "fake out" the compressor to see if it stops cycling, which would prove or disprove the idea that the issue is the evap temp sensor.

Jag987 on Mon July 14, 2014 6:10 PM User is offline

Quote
Originally posted by: Frank72785
Quote
Originally posted by: wptski .......I mentioned that I had initially put 1.5lbs in the guesstimated the last half of lb because it was a 12 ounce can. So I should have been close to 2lbs. But then my inexperience came in and I bled some out. Maybe the cheap cans that I bought weren't actually 12 ounces each? I generally try to not get the stop leak stuff which this didn't have stop leak in it.


12 ounce cans are hard to get the right weight with. It is near impossible to get all 12 ounces out, and it is still only 12 ounces. Remember, a pound is 16 ounces not 12 and I bet there is a loss of 1-3 ounces per can.

-------------------------
I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

wptski on Mon July 14, 2014 6:31 PM User is offline

Quote
Originally posted by: Jag987
Quote
Originally posted by: Frank72785
Quote

Originally posted by: wptski .......I mentioned that I had initially put 1.5lbs in the guesstimated the last half of lb because it was a 12 ounce can. So I should have been close to 2lbs. But then my inexperience came in and I bled some out. Maybe the cheap cans that I bought weren't actually 12 ounces each? I generally try to not get the stop leak stuff which this didn't have stop leak in it.



12 ounce cans are hard to get the right weight with. It is near impossible to get all 12 ounces out, and it is still only 12 ounces. Remember, a pound is 16 ounces not 12 and I bet there is a loss of 1-3 ounces per can.
Watch your editing, I didn't say that. The OP did.

Jag987 on Mon July 14, 2014 6:54 PM User is offline

Quote
Originally posted by: wptski
Quote
Originally posted by: Jag987
Quote

Originally posted by: Frank72785

Quote



Originally posted by: wptski .......I mentioned that I had initially put 1.5lbs in the guesstimated the last half of lb because it was a 12 ounce can. So I should have been close to 2lbs. But then my inexperience came in and I bled some out. Maybe the cheap cans that I bought weren't actually 12 ounces each? I generally try to not get the stop leak stuff which this didn't have stop leak in it.







12 ounce cans are hard to get the right weight with. It is near impossible to get all 12 ounces out, and it is still only 12 ounces. Remember, a pound is 16 ounces not 12 and I bet there is a loss of 1-3 ounces per can.

Watch your editing, I didn't say that. The OP did.

Aw! You are right!! My bad, sorry.



-------------------------
I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

Frank72785 on Mon July 14, 2014 7:00 PM User is offline

New observations on a later point of the day lol. All I have been doing is crawling the Internet trying to learn about this ac.. When the car is freshly turned on after sitting pressures seem out of whack. Low is like 70-80 high is in the range it should be. Could the expansion valve be bad? Sending too much r134 into the system and making it too cold and tripping the evap sensor? Because the evap sensor is like said before solid state it should fail right away once that cold air gets into the box. The car has no orifice tube. The expansion valve feels like my new light of hope just trying to see if I am completely wrong on that guess?
What are the symptoms of a bad expansion valve?

Thanks again everyone for dealing with this crazy car with me.

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