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A/C Cycling - TXV?

rperry435

rperry435

New member
Exactly what the title says my car will blow cold air while driving down the road but as soon as I'm sitting still it starts to warm.

Just changed the ac condenser because it had a hole. Had the system sucked down and done by an automated snap on machine. Correct ammount of refrigerate is in the system. Fans are coming on the issue is only sitting still its just not that cold.

Any suggestions to what I should change out?

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Re: A/C Not blowing cold at idle

Guess I only notice it while sitting but I can clearly hear the compressor coming on and off reguardless if I'm sitting still. On it gets cold. Runs for a few seconds and off. Almost like a pressure issue.

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Re: A/C Not blowing cold at idle

I'm leaking at the black clamp style locking tab at the condenser. I'm swapping out the old orings and putting in a new. Also changing the Schrader valve at the fill port for preventative issues.

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Re: A/C Not blowing cold at idle

We put it on the snapon machine sucked all the refrigerant out. Replaced the leaking o rings and the Schrader. Vacuumed it down, added the 2lb 4oz (1.05kg) it calls for even used a sniffer on the whole system, no leaks... but still having an issue.

A/C blows cold while the compressor is running, low side pressure is steady at 40psi. Pump is still kicking off occasionally. I'm going to have to plug the tech2 in and see what I can find.

I'm not sure if I messed with the a/c settings in hptuners

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Re: A/C Not blowing cold at idle

I think I only messed with the delay, not sure why really it was just something I did when I first got it. I'll put those back to stock later on today.

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Re: A/C Not blowing cold at idle

The only thing I typically do in HPT to aC is set the turn off to a higher TPS. Screw power, if I have the AC on, I want AC. :cool:

What are the high side pressures looking like?
 
Re: A/C Not blowing cold at idle

I believe 150psi.. Not 100% but the machine says pressures are correct especially while the pump is running.

Just weird that it's cutting out for no reason. I still have to plug the tech2 into it but I might jump the high and low switches one at a time to see if ive got a bad one.

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Re: A/C Not blowing cold at idle

I'm going to replace the pressure sensor since I can't find any codes leading me to a problem.

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Re: A/C Not blowing cold at idle

I didn't modify anything in hpt besides the delay turn on at startup. Not sure why i did but either way still doing it. Pressure switch in the way..

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Re: A/C Not blowing cold at idle

The pressure switches are built into the PCM, and they return a 0-5v reading. You would have to emulate the correct pressure for it to "jump".
 
Re: A/C Not blowing cold at idle

Yeah there's no jumping that sensor already looked into it. Ive heard the 3pin sensor on the line be called several different things.. A/C pressure switch, cycling switch, etc. I couldn't find anywhere on Mitchell to tell me what the correct voltage is for a good sensor. GM lists for $55 and my cost is only $22 so I'm just going to replace it first. I know the pcm turns the ac compressor relay on and off and I can see the relay command with the tech2 go from on to off but a/c shows no DTCs.

Seems like the compressor stays on for long duration in the morning for first startup but gets worse through out the day. Already tested the clutch.

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Re: A/C Not blowing cold at idle

Replaced that sensor does the same thing. :confused: :banghead:

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Re: A/C Not blowing cold at idle

I'm going to do a recover and change the Accumulator. Vacuum and Charge it back up. It's a cheap part might as well give it a shot.

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Re: A/C Not blowing cold at idle

Not that anyone is paying attention to my thread but put a new accumulator on it didn't help. I'm going to try flashing stock programming with the tech2 since that won't cost anything and if the problem persists I'll buy the txv (thermal expansion valve) since it's basically the last thing to change.

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Re: A/C Not blowing cold at idle

Stock flash with the tech2/mdi yields same results. On to the txv.

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Re: A/C Not blowing cold at idle

Tech2 shows its will not engage the ac clutch upon my request because of a pressure issue. Look at my high side it shows 300+ and increasing to about 400 before shutting down the compressor after a couple seconds. I know the switch can't be bad I just changed it with a GM Part number sensor. I think the obvious would have to be the txv not opening properly causing the pressure to rise to an unsafe level.

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