Does anyone know why an AC compressor would not engage if: the freon is full, it is not locked up, all fuses/relays are okay, there is power all the way to the compressor, and the pressure is okay. We are desperate - already giving up our house b/c of the economy, we cannot afford the $160 that the dealer will charge to fix the problem, nor the $1100 they are quoting to replace the compressor if it must be fixed. Are there schematics of the Ac system available anywhere that we can take to our mechanic to help him find the problem? We live in South Florida and it’s already been 90+ degrees here. We have a small child and it is difficult to not have AC for him. Help!
Sorry, that should be “the $160 that the dealer will charge to DIAGNOSE the problem…”
Don’t go to the dealer. Find a good independent…maybe even one who specializes in AC.
If you have a voltmeter and are careful, you can check and see if power is getting all the way to the compressor clutch. Check the connection at the clutch with the AC on and the engine running. (Be careful of moving parts!) If you get 12V or so there, then you can conclude that the AC clutch is bad. If you are not getting 12V there, then it is more complicated to determine why.
Thanks, Mike
Okay, not sure what happened there to the first reply I wrote, but here goes again…
Hi Tardis: Thanks for the info. Is there any possibility of getting a copy of the schematic for this system anywhere online? Neither mechanic we visited (and to whom we’d like to give the business, because they are both great guys) was super familiar with Saturn, and neither one mentioned the clutch at all. Is the clutch an obvious part that can be seem from above when looking into the engine at the compressor? Or from below? Everything he did from above and below he did with the engine and AC on.
Okay, again, it’s not posting my notes, so here goes one more time…
The car is a 2001 Saturn L200 with 70,000 miles on it. When our mechanic replaced the fuel pump last year to the tune of $700, he said the same thing he said when I went in with the AC problem: this car is not old enough for this to be going wrong. Small consolation to know that it SHOUDLN’T be happening since it is!
There’s a poster on this board that frequently posts links to diagrams for particular cars. Maybe he’ll chime in soon. The clutch is inside the pulley that is attached to the AC compressor and driven by the engine belt. It should have a connector with one or two wires (probably two) coming out of the stationary part of it. If it is two wires, one should be ground (when operational) and the other +12V (when operational).
(The clutch is the thing that engages the AC compressor.)
If the clutch has indeed failed, it maybe that the compressor is also bad and caused the clutch to fail.
Thanks for going forward with me on this…I do hope the other poster pops up as well. Thanks for all the info. I’m going to print the page and go back to the mechanic and ask if he did go this far with it.
I’ll take a look around this evening for a wiring schematic, peruse it, and post back with hopefully helpful comments. This car may use a controller for the compressor clutch but I’ll take a look at that later today.
Your mechanic could be a bit off base on this.
The fuel pump should not fail at comparatively low miles? That depends a lot on the regularity of fuel filter changes. Even a partially clogged filter that does not affect engine performance can shorten a pump’s life.
As to the A/C, the car was likely manufactured in the year 2000. That makes it going on 9 years old and A/C leaks and problems are common on an aged car.
Hi ok4450:
Thanks so much!
No luck on schematics in my stash; all older stuff. However, I took a look at the AutoZone site schematics. Horribly undersized and unreadable so I picked one out that I thought might be applicable, enlarged it, and printed it out.
Just to clarify something, or reclarify it. There is verifiable power being provided to the clutch on the compressor; verified with a test light or voltmeter?
If so, this means there should be a dark green wire that is powered up by the A/C relay. Power flows through the clutch into the black wire which then goes to ground in several places; with several connections along the route in the underhood fuse block.
With a voltmeter or test light power should be present in both the dark green and black wires at the compressor clutch.
If power is present at the green wire and not at the black one the schematic shows that the clutch has what is apparently a high temp fuse in or near the clutch; possibly screwed into the compressor body. If this fuse is faulty the clutch will not energize.
If power does flow through the black wire and the clutch will not engage then there could be a problem with one or more of the ground connections that flow through the underhood fuse block.
The schematic also shows a diode in the fuse block. We won’t get into why and how a diode works at this point, but the odds of a diode being the cause are very, very slim.
Hope that gives you something to work with for a while. Will check back on this thread later tonight or tomorrow.