Hey all.

So I just got a 97 C5 about a week ago. Everything seemed ok but then it got really hot and when we turned on the a/c the light just blinked - tried again the light came on, blew ice for about 20 minutes and then went off again.

So searched around did all the troubleshooting, took it in tested for leaks etc but nothing. The system showed fully charged, no leaks, compressor is good etc.

I have had two place look at it plus all the knowledge I have gathered from here and my google-fu and I am coming up empty.

So basically here is where I am at.

I can turn the a/c on, get ice cold air, then between 5 minutes and say 30 minutes that light goes out and the a/c goes off. It will not come back on again no matter how much I try - if I press the button again it will blink and then go off - after sitting for 8-12 hours I can repeat this process. Works, off, blinks & off etc.

I tried pulling codes from the info center all the DTC stuff and there is nothing there for it.

Anyone have anything like this happen before? Advice? Ideas?

 

Sounds like a relay is getting hot and when it cools off it works again till it gets hot and quits?

 

compressor going bad, see a professional to confirm.

 

Relays checked and even swapped but still same results. I haven't replaced them with brand new ones yet though because I didn't think it would be root cause. Should I?

 

Brought it to the shop already they confirmed compressor was good and no leaks in system

 

Maybe this can help, I used it and found it to be bad relay. (my light would blink a couple times and go out)

 

Maybe this?
https://www.amazon.com/ACDelco-15-40...rvettewebce-20

 

That is a TON of info ... wow! Thanks for this!

 

I was wondering the outcome of this? I am having the exact same issue on a 2001 C5 Lingenfelter with 55,500 miles. My neighbor's friend was a 30 year GM mechanic. He said to evacuate and pull down the vacuum in the system and then recharge. I just had that done that today and replaced the high pressure switch a couple days ago. No improvement yet. He also said if that doesn't do it he would be looking at a new compressor. From what I've read the Corvette's up to 1996 C4 gen had a low pressure switch but, in 1997 C5 they started using a variable valve compressor which eliminates the low pressure switch. Replacing the compressor also means replacing the accumulator, orifice tube filter, and I've heard it's a real good idea to replace the condenser too. I presume because it's nearly impossible to flush it due to the small openings of the mesh, or fins. Flush, evac, and refill. High or low pressure, and a low pressure switch are the common answers to a clicking compressor clutch which when it goes on and off the ac button light does too. I've watched the high pressure sensor voltage with my HPTuner while it was going through the problem and while the AC is working for the first 20 minutes or so the voltage is 1.9-2.2 volts. When it quits it's about .90 volts. I've read that the sensor outputs 1 volt per 100 psi roughly and that would make sense with my physical gauge readings. The AC compressor is obviously shutting off going down the road and the lines are returning to ac off pressures.

 

go though the doc. I provided in a earlier post and do the step by step process, like I said mine did just what your describing and it was the ac relay, or just put a new one in and see, it's the cheapest part in the system !!!!

 

I appreciate your reply. I have seen the steps in the doc in a 1999 DVD factory service manual I bought used off eBay. I haven't been through the voltage and ohm checks but after posting I tried jumping the 30 and 87 pins of the relay and that seems to keep it on but I couldn't make it the 20 or so minutes I was hoping to because the car idle was surging. I'm not sure why this is but when I removed the jumper it went back to normal idle. It acted much like when I bought the car and it had an underspeed idle which I fixed with an HPTuner by upping the idle to 1100 and increasing the stall saver reaction times in the PCM. The two other posts normally connected by the relay weren't connected to anything when jumped. I didn't notice this behavior the other day at idle. It only surged when I drove it during decel. Back on topic - I swapped relays with the fuel pump because I figured I would notice if the fuel pump was cutting out. No fuel issues and same AC issues. I just learned of the DTC code reader in the car's dash so I went looking through these. I cleared all of them as the car has had five owners and I haven't had it long. Now that I think back the light may have flickered a time or two over the winter but I wasn't calling for any cooling. I probably just noticed it when hitting defrost or playing with the controls. I haven't had the battery out, or even disconnected the battery, or fuses, to try to let the charge drain off the components. I haven't looked these up yet but here are the DTC's I'm getting. One related to HVAC about a left actuator out of range, and a couple PCM codes returning right after clearing them. They are marked H and C for history and current as I understand it. On a Bosch reader the other day I had a PCM lost communication after clearing I believe so we'll see if one of these is that. Since I cleared the codes I took it out with intention to get on the highway to heat it up but, the AC wouldn't come on from the start after the car had been off for a couple hours. The AC light doesn't always flash either. This time I got 3 timed flashes and then off. Subsequent presses resulted in a solid AC light for a few seconds and then off without flashing.

PCM
P0103 H C
P1546 H C

99-HVAC
B0441 H C

 

I stored my 1999 Corvette last year with my account in working condition. Now that I have uncovered it my AC light just blinks and then turns off when I push the AC button.

 

I finally resolved this. The first thing I checked was the AC Clutch relay when I started all this. I couldn't get it to do anything by wiggling it, or swapping with another. On the auto climate control cars the relay is powered when ground is sent from the PCM. On the ignition feed side the hot is always hot. When ground is sent the switch is closed and power is sent. If I grounded the wire in the relay coming from the red PCM connector pin 43 my AC clutch would come on. I replaced the PCM and flashed my tune onto it (yes, it cost me two HPTuner credits even with VIN programmed by eBay seller) and then the relay would work only if I put pressure on the top. I bent the pins out in both directions (important to do both in my case) and it has worked like a charm ever since. I think my problem was two problems. The PCM and the relay. There are things that can cause the PCM to shut off power. Stall saver, high coolant temp, high pressure ac switch, etc. I notice that the AC relay gets hotter than others and I've read that it's actually 12 volts on both lines going into the AC clutch. My AC relay was much easier to pull out than any of the others. I'm guessing the heat might have caused the connectors to expand. The problem is getting to them to fix them. It's hard to get the fuse box to turn all the way over with all the wires connected to it. I tried. For now, bending the relay pins is working so I'm calling it good.

 

I am going to throw a monkey wrench into the mix, I have a 98 base model coupe, auto trans., with a manual AC controller & no digital temp display of any kind or code displayed. Bought the car last summer & immediately had to add r134 & that worked just fine. this spring when temps began to warm up had to do the same thing, again worked ok for a short while. now all of a sudden nothing. my friend that runs a shop checked the ac for me & found the clutch was engaging on the compressor, the system was actually over serviced with r134 so he took some out & got it working. worked ok for 1 day now back to no ac at all or intermittent cold air. What's really odd is that sometimes after driving around for 30-45min. then u will start getting cold air???? All during this time no diagnostic codes & temp is ok. Is it electrical or is a failing compressor, or should I just go ahead & eat the cost of a compressor & the parts that make up an ac repair kit??? Need ideas please!!!