rmarks

Plenty of pressure. Checking voltage on input to clutch - is 12 volts but the unit engages and disengeges. When engages, plenty of cold, but disengeges a lot (again with 12 volts coming into the unit).

Obviously something in the unit. Can I replace just the clutch unit or do I have to depressurize the system? Can I do it on the car. Mechanic I go to (when I don't do it myself) says you have to pull the compressor?

Help please.

Dano523

System has a high pressure switch, and if the pressure is too high, then when the system heats up and the pressure increases as well, the high pressure switch will kick the system out.


So what is your pressure readings???

rmarks

Where is the high pressure switch located please?

Dano523

Here are the pressure charts,
http://www.mediafire.com/view/6hw61h...ure_charts.pdf

So again, what are the actual pressures at what temps, since if the Freon pressure is too high, it going to kick out the system so it does not blow the lines.

Hence as the system works, it heats up the Freon which increases the pressure, and again, if the pressures get to high, it will blow the lines. So the pressure switch is used to monitor the pressure, and if the Freon gets too hot at normal pressures, it shuts the system down to the pressure can drop. If the pressure is too high at cooled temps, then as the system begins to kick in, even a slight temp raise will cause too much pressure to kick the system out quickly instead.


So at this point, with the compressor kicking out, does scream that the shop has the Freon pressure to high to begin with, and what is causing the problem as the Freon in the lines heats up to case the system to kick out due to over pressure problems.

Since the shop is not understanding this, then time to take the car to the dealer that has a clue on the system instead.
Note if the car was tuned, then someone may have screwed around with the A/C kick out setting, and could also be the problem instead.

rmarks

I spoke with the shop, they know their stuff. OK Jose rides one of his 2 Harley, not a Corvette, and he is real smart. He forgets the pressures but said they were good. He sees a lot of AC systems.

He said: "it runs for a while and then when it gets hot it cuts out. But there is still 12VDC directly going into the compressor". I questioned him and he said that they are measuring power going directly at the compressor. So there is something in the coils that is screwing up.

Any help?

schpenxel

I think they're wrong but what do I know

The clutch can be replaced without release any refrigerant. It's not a fun job but I have done it so I know it can be done. New clutch was about $100 on Amazon.

Dano523

Ditto, the clutch is not that hard to replace,



But a quick test to make sure that its the clutch that is having a problem, connect a 12V source to it's connector to see if it will hold engage or not.

When the clutch coil goes, it not a spotty thing, but a constant thing of not engaging, and still think that its a pressure problem with the high pressure switch kicking the compressor/system off so the high Freon pressure does not blow the lines instead.

schpenxel

Agree.. why don't they check to see if the power wires going to the compressor is being turned on/off or if it's staying on and the compressor is going off?

That should nail down whether the clutch is doing what it's told or not

I don't think the compressor is the issue. I don't care what the AC guys says.

TX-Techman

How long does it run before it shuts off? My bet would be you are low on Freon and the low pressure switch is disengaging the clutch to prevent damage. Once it shuts down on low pressure the pressure equalizes and the clutch engages and it will run until the pressure drops and it goes off on low pressure again. If this is the case depending on how low it is the compressor will run maybe a few seconds to longer and the ambient temperature would affect the run time as well.

Mike's LS3

I had a Hi-temp pressure switch replaced when the AC would start blowing warm air. There was no CEL, but if you have a DTC code reader it might display a DTC code to troubleshoot.

cclive

I agree that if it is the clutch itself, it would be unlikely to be intermittent...it would either work or not. For the price and ease of a $20 gauge, I would want to see the pressure myself.

Dano523

And again, scroll down to the bottom of the below link/dowload chart and it lists the correct high and low pressures at the air temp that car is at.

http://www.mediafire.com/view/6hw61h...ure_charts.pdf

rmarks

OK, here is the final result.

1 - Put in a new pressure override switch - did NOT help. Like I said, there was 12vdc going into the clutch and operation was intermittent; smells like the AC clutch to me.

2 - Changed the AC clutch and all worked. Nuff said. Did it by removing the compressor and breaking the pressure seal.

Some commented that the AC clutch could be changed without removing the compressor. They could not get in there well enough to do the job. The shop said that, maybe an individual could do it if he was working on it for hours, but the shop works on cars all the time and cannot mess around and wants to make sure it is a quality job. I totally agree.

schpenxel

Good to hear you got it fixed.

I have changed the clutch with the compressor still installed.. but they are right, it was a total PITA and I wish I had just pulled the compressor and either replaced it off the car or just replaced the whole compressor. There are some snap rings you have to get off and doing that in the car is not much fun.

Hindsight, as they say...

kcotte59

I must disagree. Replacing the compressor clutch is about 10% of the work to replace the compressor. Plus no refrigerant is involved. I have removed the compressor clutch on my 07, had to remove a radiator hose that is all. You might have to unbolt the compressor and reposition it slightly if you have trouble getting the pulley snap ring off. Removing the compressor entirely is an ordeal, many other things need to be removed first. Quality is no better if compressor is removed or not, and why would it matter anyway?