As the title says, I picked up a 2000 SL1 4dr 5 speed with 101,000 miles yesterday for $1500.00. The car's history was a 15 mile commuter everyday since new. Every thing works except the A/C compressor clutch. Still had the original owner's manual in the glove box along with every maintenance receipt for the car.

So, without looking at my 1994 saturn books, that are about an hour away, does anyone know if I can get just the compressor clutch, or do I have to buy a complete compressor? I am HVAC certified, so no problems on swapping the compressor, just wanted to save a little money.

Thanks,
Rob

 

As you are an hvac guy, I am not trying to insult your intelligence nor training.
Have you ensured that the low side pressure is at least about 35? Otherwise the low pressure switch will inhibit the A/C clutch from kicking in. (The switch is actually a combo low pressure/high pressure switch). That and the A/C relay would be the things I'd check if not done already.

 

Yes sir, hooked a set of gauges to it and verified that it still has a charge. After that I went straight to the compressor clutch wire. I have 14VDC potential when the air conditioner button is on, and I have 0VDC when the air conditioner button is off. Also the radiator fan comes on like it is supposed to if the button is on. Thanks for the helpful info. I have found a remaned compressor on ebay for 159.00. That and a new AC Delco filter dryer should set me up.

 

Before you go that route, Rob, why not just call a few of your local parts stores and see about getting a clutch? No need to open the system if you don't have to. I'm a cheap basta...I mean frugal person and that's what I'd try. As far as I know, most a/c clutches are replaceable.

 

Trust me, I am a believer of leaving a system closed, but the clutch alone was over 200 dollars. That and I would have to purchase a 3 blade spanner wrench as well. I have a lot of tools, just not a 3 blade spanner wrench. I have the R134a, gauges, and the vac pump. I just hate to invest in a clutch, just to find that the compressor is jacked as well.

 

When you checked the compressor wire for voltage, was the wire still connected or disconnected? This may sound stupid but if the wire was disconnected, you could still have a bad relay, especially if you were checking for voltage with a digital voltmeter. A DVM will feel voltage through a bad contact because it does not load the circuit. If you probed the wire and got 14VDC, that indicates that there is an open at the clutch coil.

If the clutch was mechanically bad and you probed the wire, you would have gotten a much lower voltage, maybe close to ground potential, but you would only have it momentarily as the fuse would blow in short order.

Before you go and replace the clutch, try removing the clutch relay from the underhood fuse/relay panel and jump the contacts with a bare wire and see if the clutch tries to engage. I believe the hot contact is hot all the time, the coil is activated by the BCM. This is the only surefire test that I know of for checking the clutch. The clutch relay is problematic in this series. I think it's the same one used in Toyota's, where it is also a problem.

If the clutch still doesn't try to activate, look for the wire coming out of the clutch that is grounded to the compressor and make sure it is OK. I'd hate to see anyone change a compressor clutch for a loose wire.

 

Man, these are all good points. I checked the voltage with the wire unplugged with a Fluke DMM. I think I will check everything before I commit to changing the compressor. I have already ordered the compressor, but I could just seal it up and keep it for a spare. It just sucks that the wiring schematic in the book is horrible. I never would have thought that the BCM controls the a/c. I'm used to the pressure switches regulating the compressor.

So, if the relay is bad, my pressure switch is good, and my charge in the system is good, I could run the a/c system like that, just would not be able to turn the a/c off with the button on the dash, right?

(Nevermind, my guess is the pressure switches activate the relay, not the hot wire going to the compressor.) edit

 

Ok, update time. So on my particular car, I have the same Siemens relay for my compressor as I do my horn. I swapped those relays, because my horn works. With the relay in, a/c button in the on position, and tapping the wire going to the clutch, I have 14VDC at the wire to the compressor. I also had my negative lead on the clutch body, so that rules out a compressor clutch ground issue. Unplugged the pressure switch in the system and the radiator fan went off, jumped the switch and the fan came on. Pulled the jumper off the switch and the fan went off. Plugged the wires back into the switch and the fan came on again. I'm thinking this indicates that the BCM is acting correctly. I'm still saying compressor clutch.

Edit:
I guess I could have verified that the coil was bad on the clutch by doing a continuity check from the terminal on the clutch to ground.

Thanks for all the help and suggestions.
Rob

 

Either that, or run a wire with a switch directly from the battery to the clutch actuation terminal ...

 

Jumping the contact terminals on the relay block is the same as taking a wire directly from the battery to the compressor wire. The BCM is in the circuit because the AC not only needs input from the pressure switch, it also used inputs from other sources such as manifold vacuum. I.e. low manifold vacuum from WOT, like going up a steep hill cuts off the compressor. But if you swapped the relay with a known good and it didn't come on, that pretty much eliminates the relay. The FSM really sucks when it comes to the AC system.