Calling all car AC gurus...

[Bignate603]

Car AC isn't something I normally mess around with so I figured I'd ask around before diving into this. The AC on my 97 Chevy venture went out a few days ago. It appears that the AC clutch isn't engaging. (push AC button inside the car, compressor never spins up).

I pulled the connector from the AC clutch and checked the voltage across the two lines going in (one black, one green, double checked to make sure green is ground by checking continuity with the frame) while the AC was switched on, I'm only getting 0.5 volts at the clutch. That makes me think I've got a bad fuse or relay somewhere upstream of the AC clutch that's preventing me from getting power to the clutch.

Before I dove in and replaced all the fuses and relays having to do with the AC clutch I wanted to make sure that this was the likely culprit. Does anyone know if there is any other reason why I'd only be getting 0.5 volts at the AC clutch?

It would be really nice if I could fix this with a fuse or relay, I'm hoping that's not just wishful thinking.

 

[1prophet]

Car AC isn't something I normally mess around with so I figured I'd ask around before diving into this. The AC on my 97 Chevy venture went out a few days ago. It appears that the AC clutch isn't engaging. (push AC button inside the car, compressor never spins up).

I pulled the connector from the AC clutch and checked the voltage across the two lines going in (one black, one green, double checked to make sure green is ground by checking continuity with the frame) while the AC was switched on, I'm only getting 0.5 volts at the clutch. That makes me think I've got a bad fuse or relay somewhere upstream of the AC clutch that's preventing me from getting power to the clutch.

Before I dove in and replaced all the fuses and relays having to do with the AC clutch I wanted to make sure that this was the likely culprit. Does anyone know if there is any other reason why I'd only be getting 0.5 volts at the AC clutch?

It would be really nice if I could fix this with a fuse or relay, I'm hoping that's not just wishful thinking.

There is also a low pressure switch that opens if the refrigerant level gets too low pressure wise to prevent the compressor from turning on and burning up.

 

[Bignate603]

There is also a low pressure switch that opens if the refrigerant level gets too low pressure wise to prevent the compressor from turning on and burning up.

Ok, so I should check the freon pressure before I do anything else. I'll see about scrounging up a pressure gauge to check that.

 

[BUTCH1]

There is also a low pressure switch that opens if the refrigerant level gets too low pressure wise to prevent the compressor from turning on and burning up.

I've had that happen, the compressor engages for a few seconds then cuts right out, OP, a few things happen when the AC is turned on, the electric fan should start immediately and the idle speed gets bumped up to compensate for the compressor being on, are any of these things happening?.

 

[Bignate603]

I've had that happen, the compressor engages for a few seconds then cuts right out, OP, a few things happen when the AC is turned on, the electric fan should start immediately and the idle speed gets bumped up to compensate for the compressor being on, are any of these things happening?.

I'll check if the electric fan comes on but I haven't noticed a change in the idle or anything else.

Whatever is happening it's preventing power from getting to the clutch relay. I used a set of wire leads and a multimeter, the relay isn't getting triggered so its happening earlier in the circuit than the clutch relay.

 

[HarryLui]

When you're tired of working on it, take it to this place. He'll treat you honestly and with respect.

http://www.yelp.com/biz/ajs-auto-repair-mesa

The a/c clutch would not engage if you have a low level of R134A. You most likely have a leak in your a/c system.

 

[Bignate603]

When you're tired of working on it, take it to this place. He'll treat you honestly and with respect.

http://www.yelp.com/biz/ajs-auto-repair-mesa

The a/c clutch would not engage if you have a low level of R134A. You most likely have a leak in your a/c system.

I use Ronnie's Auto in Tempe. If I can't figure it I'll take it over to him.

 

[BUTCH1]

I'll check if the electric fan comes on but I haven't noticed a change in the idle or anything else.

Whatever is happening it's preventing power from getting to the clutch relay. I used a set of wire leads and a multimeter, the relay isn't getting triggered so its happening earlier in the circuit than the clutch relay.

You might want to check the low pressure switch by temporarily jumping across it and see if the clutch engages, if it does don't run it very long to avoid damaging compressor. If it blows cold you've found the problem. A long shot, might be the switch on the dash, cloud be a pain to get to (depending on the car)..

 

[bruceb]

I tend to agree, your system has lost most or all the freon charge. If that is the case, the leak needs to found and repaired, vacuum pumped to remove air and moisture and the proper freon amount weighed into the system. Cars with R-134A systems are very picky about using the designed for amount of refrigerant. Too much or too little will cause the system to not perform as it should.

 

[Meghan54]

I tend to agree, your system has lost most or all the freon charge. If that is the case, the leak needs to found and repaired, vacuum pumped to remove air and moisture and the proper freon amount weighed into the system. Cars with R-134A systems are very picky about using the designed for amount of refrigerant. Too much or too little will cause the system to not perform as it should.

Either that or the low pressure switch itself is bad. That's what happened to our AC on our Blazer. Worked one evening, didn't work the next startup that following morning.

After checking fuses, relays, jumped out the low pressure switch, instantly came on and was as cold as ever. Replaced switch, working perfectly. Did refrig. pressure after replacing switch but it was fine. Just a bad switch and a cheap and easy fix.

 

[hanoverphist]

I use Ronnie's Auto in Tempe. If I can't figure it I'll take it over to him.

i use AZM Tint for pretty much everything. they do tons of AC repairs and replacements. in mesa. hes one of the few mechanics that actually told me what i didnt need when i thought i knew what was wrong.


and i agree it sounds like a relay or switch issue if the level isnt too low.

 

[SuperSix]

Put a set of gauges on it first, and see if you still have any freon. The fans/etc won't come on if the system is los on freon, jumpering the low pressure switch BRIEFLY should make the clutch engage. BRIEFLY, because if you are low/out of freon, you may be low/out of compressor oil. And don't use leak sealer, that's just a quick fix that could cost you dearly later.

 

[BUTCH1]

Put a set of gauges on it first, and see if you still have any freon. The fans/etc won't come on if the system is los on freon, jumpering the low pressure switch BRIEFLY should make the clutch engage. BRIEFLY, because if you are low/out of freon, you may be low/out of compressor oil. And don't use leak sealer, that's just a quick fix that could cost you dearly later.

Good idea, you keyed on the word "briefly", if OP finds this is the case he should re-charge immediately. OP still hasn't responded to as how the system was performing before it quit..

 

[Bignate603]

Good idea, you keyed on the word "briefly", if OP finds this is the case he should re-charge immediately. OP still hasn't responded to as how the system was performing before it quit..

It was working ok right up until it quit. It took a while to cool off but when the car is over 120 degrees I didn't think that was odd.

I borrowed a cheesy parts store AC pressure gauge from a friend but it doesn't seem to be working. It reads zero pressure but it doesn't seem like it is seating correctly on the fitting. There's definitely pressure in the system because you can tap the valve core and you can hear pressure escape.

 

[LTC8K6]

I would just recharge it with a store kit and see if it starts working. If it does, you have a leak to find.

 

[Bignate603]

It's official, I've got a leak. I tried another pressure gauge and that read zero also. I pushed the valve stem in all the way and I only got a very weak hiss, very little pressure.

The blue book value on this car is almost nothing and we're planning on moving in a few months without bringing this car along with us. I think I'm just going to deal with it for a few months and then dump the vehicle cheap on craigslist when we move, list for something like $1500 and the first person with $1000 in cash can take it.

 

[BUTCH1]

If it's just an o-ring won't be too bad but like you said, summer's almost over and it is a '97, see if an AC shop will give you a free estimate to fix it.

 

[Bignate603]

If it's just an o-ring won't be too bad but like you said, summer's almost over and it is a '97, see if an AC shop will give you a free estimate to fix it.

Even if it is an easy fix I'd still have to get the AC system flushed to remove moisture and refilled with the refrigerant. At the minimum I'm looking at a few hundred which I'm not willing to put into this car.

 

[alkemyst]

check out http://www.youtube.com/user/richpin06a

He helped me do my wife's saturn a/c for about $300 vs $1200 at a shop...took me about 2 hours.

 

[Bignate603]

check out http://www.youtube.com/user/richpin06a

He helped me do my wife's saturn a/c for about $300 vs $1200 at a shop...took me about 2 hours.

Nice link, I'll save that for other jobs but I'm not going to be doing anything else on this one. I've decided I'm not really interested in spending any more time or money on this car. A few hundred bucks and a weekend to track down the leak, get the parts, and then replace them is not worth it. I'd get a a few weeks of AC before it got cool enough I can get by without it.

It will get sold in a few months when we move and I don't have a problem letting it go cheap. This thing paid for itself in the first month I owned it, we bought it because it cost the same as renting a u-haul to move cross country. Getting 4 more years out of it was just icing on the cake.