CaddyInfo.com

A/C Repairs

Various Owner Notes

When the compressor won't start, often it is the compressor clutch or coil that has gone out.  These can be replaced separately and more cheaply than the entire compressor.  The compressor retails for $671, plus usually a markup of 30-65% from the mechanic; the cheapest I have seen are around $360 delivered.  The compressor clutch and coil together cost around $80 plus S&H, so a definite savings.  Also if you can replace the clutch/coil without getting into the refrigerant, so it is a much easier home repair.  Try gmotors.com, gmpartsdirect.com, and parts.com for discount new parts.

This page is a collection of posts relevant to this topic.   Chris's first post is good detail on the process.  In Chris' case, he went all the way and just replaced the bearings within the compressor clutch.   However, the same approach would apply if you intend to replace the clutch/bearings as an assembly, or need to get in to replace the clutch coil.

CHRIS wrote: Same exact problem on my 94 STS 6 months ago.   $14. for a new bearing or $350. for a new compressor.  It's a fairly easy and straight forward job,  BUT  you will need a hydraulic press to press the new bearing back into the pulley, and the GM pulley puller and reinstall reverse puller.  Begin by taking off right front tire and removing plastic wheel well.  It come out in 2 pieces and you gain access to engine compartment. Remove serpentine belt. There is a "C" clip on the inside of the compressor pulley - remove it.  I believe there is a nut on the compressor shaft that comes off next.  Now the pulley with the bad bearing will pull off with the use of the GM compressor pulley puller. Remove shot bearing from pulley and press new bearing in. You will need the GM reinstallation tool to get the pulley back on the compressor shaft. YOU DO NOT WANT TO HAMMER THE PULLEY BACK ON THE SHAFT CAUSE YOU'LL RUIN COMPRESSOR SEALS. No need to remove freon or compressor, just the pully.  WELL YOU HAVE FUN NOW!!     chris
--------------------------------------------------------------------------------
If there are no codes and all fuses are good check the voltage at the compressor with a test light and see if there is 12 volts to the compressor when it is supposed to be on.
If you enter the onboard diagnostics you can check the AC compressor status by looking at the onboard display.....
Engine idling,AC on auto....after simultaneously pressing and holding the OFF and WARMER buttons the diagnostics will activate and automatically display the codes...if any.   After the codes are displayed the DIC will prompt you with PCM?  Answer yes with the HI button.   Now you will be in the PCM section of the onboard diagnostics.  
At this point the icons on the climate control panel will indicate certain PCM functions and status.   See below...
The front DEFROST icon is the AC clutch status.   If the DEFROST icon is lit then the PCM is commanding the AC clutch on.   If the AC command is lite but you are getting no voltage to the AC compressor then you are on to something !!!!
If the DEFROST icon is not lit and you are sure the AC should be on then procede....
Press the OFF button once to back up thru the onboard diagnostic menu.   After pressing the OFF the system should prompt you with IPC?  If not then press OFF again.  Once it says IPC? then answer no with the LO buton.   Then ACP? will show up.  Answer yes by pressing the HI button.   At this point the ACP status will be indicated by the icons on the climat control panel.  See below...  
The AUTO icon is the recirc mode door status....AUTO on means recirc, AUTO off means out side air.
The front DEFROST icon indicates AC clutch status.  DEFROST on means the clutch is requested.  If the clutch is not being requested despite the system being on then something is wrong.  Either the system is low on freon or there is another problem.   A code should be setting.
The rear DEFOG icon  is the compressor low pressure switch status.   If the DEFOG icon is on then the switch is open (low pressure), switch closed is icon off.   This is something to check.
The LO icon is the defrost/AC mode door status.  If the icon is on the mode door is in AC.   This won't keep the AC from working.
The HI icon is the air up  solenoid.   If the icon is on the solenoid for the air up is energized.  This won't keep the AC from working....
The FOG icon is the air down solenoid.  If the icon is on the solenoid for the air down is energized.   This is not important for now either.
Maybe there will be a clue here someplace.

--------------------------------------------------------------------------------
A coil does not function as fixed resistance.  A coil will act as a choke when the proper reluctance is inserted, and additional resistance will be seen by the circuit.  In this case the reluctance is the clutch plate which must move closer to the coil when called for, or the coil will burn out. Frequent cycling of the clutch, say 6-8 times a minute, would also burn the coil up.   The initial draw will be much higher but will be reduced when the clutch plate is pulled in.  you could prove this with an ampmeter by wedging the plate with some carboard and then read it again when pulled in.
Regards, Jim Friesen