GenVibe - Community for Pontiac Vibe Enthusiasts

I have been reading a lot of posts on here about the clutch not working and how to determine that it is in fact the clutch and not something more basic. I have a 2004 Pontiac Vibe base model. The clutch is not engaging when I turn on the a/c. I have tested fuses and relay. When I pulled the wire from the compressor and tested it for 12v it has 12v no problem. Is it safe to say that since the wire going to the compressor has 12v the clutch is most likely at fault?

I have tried moving the clutch when the car is off and it will spin by hand. Any help you can give would be appreciated. Thank you.

The most likely cause of the clutch not engaging is lack of pressure in the system. If the pressure sensor doesn't detect sufficient refrigerant pressure, the A/C won't engage. Test the low side pressure. If it's low, there's a leak in the system that needs to be fixed.

kumquat wrote:The most likely cause of the clutch not engaging is lack of pressure in the system. If the pressure sensor doesn't detect sufficient refrigerant pressure, the A/C won't engage. Test the low side pressure. If it's low, there's a leak in the system that needs to be fixed.

Is there a certain type of gauge I need to get to test the pressure on the low line? What psi is normal?

Phacade wrote:

kumquat wrote:The most likely cause of the clutch not engaging is lack of pressure in the system. If the pressure sensor doesn't detect sufficient refrigerant pressure, the A/C won't engage. Test the low side pressure. If it's low, there's a leak in the system that needs to be fixed.

Is there a certain type of gauge I need to get to test the pressure on the low line? What psi is normal?

Yes, you need an refrigerant gauge. The compressor will kick on if the LP side is between about 20 and 40 psi.

If the clutch doesn't engage, it could be any number of things:

Insufficient refrigerant
Broken pressure switch
Broken clutch
Broken compressor (often leads to LP being too high)
Electrical problem
A/C switch in the cabin

That's all I can think of at the moment. Realistically, this is one of those things you'll probably pay a lot less to have professionally diagnosed. It can be very difficult to find refrigerant leaks and it costs a bunch of money every time you charge up a leaky system in the attempt, plus you need some relatively expensive gear for it.

My suggestion is to take it to a local mechanic.

Phacade wrote: When I pulled the wire from the compressor and tested it for 12v it has 12v no problem.

You have 12V reaching the clutch, and the clutch in not engaging. This could be caused by :
1. The clutch is bad
2. There is corrosion on the clutch electrical connector terminal, so that the 12V is getting to the end of the wire, but not making across the connector to the clutch. You could try using a little sand paper or a piece of an emery board to try to clean the contact on the compressor, but I doubt this is the case. Still, I'm cheap, and would try this before spending money and time on a new clutch.
2. There is no ground. The clutch only gets one wire, which is 12V to engage, open to not engage. This circuit requires a ground for the clutch to activate. It gets this ground from being bolted to the engine, which is also ground. If this were the case, either the engine is not grounded, or there is corrosion between the compressor and the engine preventing good electrical contact at the mounting surfaces. I'd be inclined to highly doubt that either is the case. Still, to verify, you could connect a ground directly from the battery to the compressor case to rule that out.

I think that worrying about pressure in the system is premature. It might be low, it might be ok. Could be high. It Doesn't Matter Yet. Your testing shows that the controls are trying to turn engage the clutch, and the clutch is not working. You pretty much need to fix that issue before you need worry about any other issue that may or may not be in the system

sounds like a bad clutch to me, but that's from my perspective here across the ether, and as much as I hate to admit it, I can be wrong sometimes

Voltage is only one part of it. Current is what is needed to energize the clutch coil and make the clutch pull in. Have you checked the resistance of the clutch coil? Read the following link as it may help you figure out what part is bad:
http://www.freeasestudyguides.com/ac-cl ... -test.html

You still have a outside chance of the controller/relay being bad and not letting enough current through to the coil. Your voltage reading is just the wire hanging out in the open with no load on it...meaning the coil connected. If you put a load on the wire, meaning hooking the clutch coil back up and the voltage drops, then you do not enough current. This would then lead to the controller / relay or something back that ways as the problem.

I'll add another source of info about testing an A/C clutch: http://www.4s.com/Upload/Four%20Seasons ... 20DIAG.PDF