VintageAir Gen IV Magnum issue

[parsonsj]

I'm hoping I can describe this problem correctly. New system installed 3 years ago. Has worked perfectly til the customer complained about warm air.

Hook gauges up, I get 100psi on both sides. Start engine, turn on AC. Nothing. So I jump the binary switch, compressor kicks on, and I get 150 high side, 30 low, 58 degree air (80 ambient). I add 6oz refrigerant, pressure goes to high 200, low 35, still 58 degree air.

I remove the jumper on the binary switch.

All is well for about 5 minutes. But then the compressor kicks off and the blower fan stops too. I stop the car, restart it, all seems fine again. Same pressures/temps. I add 2oz of refrigerant, pressure goes to 225, low at 35. Air temp to 51. I add another 2oz of refrigerant, pressures go to 250, low 35. Air temp the same. I add another 2oz, pressure goes to 275, low 35, air temp to 56.

Then it does the same thing: compressor kicks off and so does the blower fan. I turn the car off, and the high side goes to 150, low side 50. And stays there.

And the air temps seem too warm for these pressures. I had a multi-meter on the AC request wire coming from inside to the binary switch. It went to 0V, so something inside the car is turning the compressor and blower fan off, not the binary switch.

What's going on? Anybody got a clue? I've never seen a pressure difference like this with the car off... and I've never had a car stop the compressor and the blower fan.

thanks!
jp

[parsonsj]

More diagnosis: I think this problem is electrical. Once the pressures stabilize, the AC tries to go to its ordinary cycling. As the cycling happens (high pressures oscillate between 275 and 200, it gets slower and slower, and every time it cycles off, the fans stop too. I'm stumped.

Time to call Vintage Air tech support.

[parsonsj]

And: the power leads and grounds are connected to the battery. I have replaced the 30A circuit breaker with a 30A fuse (which is intact).

[dontlifttoshift]

Do you still have the power relay or did you wire around it? You need to solve the "system shuts off" problem first.

[parsonsj]

Donny, I agree. I think it's the electronic control module in the evaporator. I'm hoping to get some VA tech support to help isolate that. I've already told the customer that we're probably looking at a new evaporator plus R&R labor.

Once that's solved, then it'll be time to look at why the car is only getting down to 56* air temps...

The thing that sucks from his point of view is that the car only has 1900 miles in the 3 years since I finished the car.

[cpd004]

I believe the first time you added refrigerant brought it up to the correct value (2X ambient + about 15-20%). Did you make sure the refrigerant you chose had no oil added to it? Also, testing should be done with a fan blowing on the condenser. It almost sounds like a faulty heater control valve. How is the connection there?

[parsonsj]

One thing to try today is to pinch the heater hose to see if that will lower the vent temps... but as Donny put it, until I figure out why the system quits, there's not much point.

And yes, I hear ya about a potential overcharge, but I'm only seeing high side pressures at about 275. Too much oil occurred to me as well..

What I really need right now is some kind of diagnostic code in the ECU that will tell me why the system is shutting down.

[dontlifttoshift]

You don't have to change the evaporator, the ECU is right on the top and you can swap it pretty easily after the glove box is out.....if that is what it needs.

.....and check that power relay.

[parsonsj]

Donny, there's no power relay. The original harness came with a circuit breaker... is that what you mean? Or do you mean the compressor relay? I changed the breaker to a fuse, and its fine. The compressor relay is also fine.

Hope that makes sense...

[dontlifttoshift]

I'm stupid, talking about a GEN IV with the GEN II diagram in my head.

ECU is still easy to change ;)

[parsonsj]

lol, I understand! Where is Ryan (KUL FIR CHKN) when you need him?

[parsonsj]

And so Ryan figured out what was wrong: the controller face plate was grounding one of the circuits on the controller PCB. For whatever reason, the nylon self-retaining washers that keep the face place from touching the PCB were missing. I can't believe I removed them, nor can I fathom Vintage Air forgetting to put them on.

Anyway, V/A is sending new washers, and preliminary testing shows the AC is working perfectly now.

Thanks for all the help everyone!

[eville]

gotta love the easy fixes after hours of chasing your tail...