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