1990 Trooper w/ 2.8 v6. When a/c is on, and idle is under 1000 rpms, the compressor spins and sounds just like ICE IN A BLENDER. When rpms go over about 1000, clutch engages and noise goes away. A/C blows cold. I know that the previous owner changed the compressor, and it is prob. converted to r134. If I can get away with just changing the compressor's clutch, I'd be saving money and time. If anyone out there has experienced the same phenomenon, please let me know. Thanks!

I think the best way to find out if it is the A/C clutch is to take a look at it when it is cycling to see if it makes noise when disengaged.

SOUNDS LIKE THE BEARING IN THE CLUTCH IS GONE, NOT A BIT UNUSUALL , JERRY

Thanks, guys. I have a feeling that it is the clutch bearing. Now, if anyone can tell me what tool(s) I need to get at that bearing...

YOU CAN DO THIS ON THE VEH, IF YOU HAVE ENOUGH PATIENCE, REMOVE THE CENTER BOLT A MM WRENCH, WILL DO AND THEN REMOVE THE FRT CLUTCH PLATE , YOU WILL NEED A SPECIAL PULLER FOR THIS ,DO NOT USE 2 SCREWDRIVERS ,YOU WIL BEND THE CLUTCH PLATE, THEN REMOVE ONE LARGE SNAP RING INSIDE THE FLYWHEEL, THEN REMOVE THE FLYWHEEL (THE PART WITH THE BELT GROOVES), THIS IS THE PART THAT HAS THE BEARING IN IT , REPLACE THE BEARING AND TAP IT BACK ON TO THE COMP SNOUT , REINSTALL THE SNAP RING, AND THEN REPLACE THE FRT CLUTCH PLATE OH DON,T LOOSE THE SMALL THIN WASHERS THAT ARE IN THE FRT CLUTCH PLATE ,THEY ARE THE SPACERS TO GET THE CLUTCH PLATE CLEARENCE CORRECT, TIGHTEN THE 10 MM HEAD BOLT BACK TO ABOUT A MAX OF 9 FT LBS OR YOU WILL BREAK IT . JERRY

Thanks, Jerry. Your expertise is sooo much appreciated. While on the subject of A/C systems... I was wondering if shops convert the old r12 systems to r134 as a matter of course whenever a/c components are replaced.

SOME SHOPS DO CONVERT ,ON YOUR TRUCK IT WOULD BE REALTIVELY EASY AS GM MAKES THE R4 COMPRESSOR AND IS R134 COMPATIBLE CONFIGURATION , IT LOOKS IDENTICAL TO THE R12 COMP. , R12 IS PRETTY EXP TO RECHARGE A SYSTEM WITH , IF EVERYTHING ELSE IS WORKING OK, I WOULD LEAVE IT R 12 IT WORKS MUCH BETTER THAN 134 SYSTEMS, JERRY

Freeze 12 will make your 134 system cool like R-12. If it were only legal to add Freeze 12 to a 134 system without a lot of work....

Freeze 12 is ≈75% Freon 134A and ≈25% Freon 142B.