Hi Guys ...

I'm trying to troubleshoot my A/C issues, so any help would be appreciated ...

First, this is a '95 LT1 Z28 ...

When I turn on the A/C I only get hot air ... and I do not hear the Compressor kicking on (nor do I ever feel any sort of surge that is often observed with the A/C system starts) ...

I checked the PCM for codes via my LT1 scanmaster and it's showing no codes ...

I added more refrigerant to the system and this didn't help ...



What are some troubleshooting techniques that I can use to ensure the compressor is faulty before replacing it ???

Thanks

 

Do you have a set of manifold gauges? It will be tough to do a diagnostic without them. Haynes has a good book on A/C repair and AutoZone has a good DVD on A/C repair.

If you know there is enough freon you can make sure the compressor is getting the signal to turn on. It make be a fuse, a relay and of course the solenoid in the compressor may be defective. I'm not sure how to do it but you can jumper the A/C relay to force the compressor on.

Here's a wiring diagram of the clutch on Shoebox's site.

http://shbox.com/1/hvac_compressor_control.jpg

 

No ... I don't have any manifold gauges but could pick some up if needed ...

I swapped out the Compressor relay but didn't notice a change ... after swapping out the relay should I disconnect the battery before retesting?

Not sure how to apply the jump ... I'll try to search on it ...

 

From the diagram I linked to, it looks like you would jumper B1 to B4.

You shouldn't need to disconnect/connect the battery though it's always not a bad idea to disconnect the battery when doing electrical work but I don't think it's necessary in this case.

The gauges aren't too expensive though they're not cheap either. I'm glad I have a set since I have about 6 cars between my kids and me.

I got mine at Harbour Freight on sale for about $30 and they do ok. They make it real nice in pulling a vacuum and putting in freon.

 

I guess a first question I might should have asked is did you have the A/C system open? If so you need to pull a vacuum and get all the moisture out. You probably should replace the Dryer/Receiver too. I used a venturi type vacuum pump but it needs a big compressor, mine is a 29 gal 160 PSI max. AutoZone lists that they have an HVAC pump available but my local stores don't have it.

 

You definitely need a set of gauges to diagnose any a/c system problems.The gauge set i have cost me almost 250 bucks, but it's specialized for the work i do. as far as a vacuum pump KYWes, i highly advise against the venturi type. yes, it works ok, but it's loud, does not pull complete vacuum, and does not completely remove moisture. just take your car somewhere, and pay a tech ten bucks to suck the system down. as a general rule, electrical is always first, then mechanical, followed by an actual refrigerant problems. check for voltage at the compressor when the a/c is on. if not, check for power at the relay and check the compressor pressure switch for wire problems. if the pressure switch is bad, it won't let the compressor kick on. if you do have voltage at the compressor, but it wont kick on, check the plug for good contact, and ground. the compressor clutch is almost bullet proof, not much will hurt it, and it rarely dies. also check for short cycling of compressor. first of all, make sure you have a charge in the system. if there's nothing in it, it won't cycle. if theres not alot in it, it will short cycle. a normal r134a system pressure while running is about 30-50 on the low side, and 200-240 on the high side. static pressures are normally around 150 lbs.

 

cuz28 - what you say is too true, however, I don't have $250 for a gauge set and the verturi type is inexpensive too. I've had good success with it but I did give it a long time to work and it is noisy. I used it about 2 hours on my system. I had replaced the compressor, the receiver/dryer. and the expansion valve. I was able to get the near 29 hg of vacuum and now I am running good high and low pressures of the numbers you quoted. I also have 40 deg air coming out the registers on a normally temperate day and it's worked for quite a while as have other cars of mine I've done.

It is best to let a trained mechanic with the proper tools do a job...however for us who like to do our own work, there are ways to do so without breaking the bank.

Our emails give the range of choices and information for help.

 

lol. good point with the price of the gauges. the cheepies at the auto part stores work just fine for car stuff. I'm a diesel mechanic specialzing in transportation refrigeration. basically, i fix semi trailer refer units, semi apu's and straight truck roof units. thats the only reason my gauges are so expensive, trust me, i didn't have the money for them either, but i had to have the fancy 4 port ones with 3 gauges (one gauge of which i added). i know the venturi vacuum pumps work good, but i don't have any expiriance with them. i just know that electric is alot better.

 

If you have a Harbour Freight near you then you can get the gauges for <$100. They also now have a nice little scroll type (real) vacuum pump for <$100. I just bought one and it works very well.

Warren