OK so working on a/c's is not one of my strong suits. In reality I've only done it once when my dad had Big Blue. We found after he had the compressor replaced, a bad seal wasn't replaced. (the old dye trick). Well the wife's 2000 Blazer has no a/c. I've checked and it's still holding a charge but the clutch won't engage when the button is pushed. Light is on, but no engage. Now when my son brought his wreck of a blazer home we trashed it. And among other things we removed totally the a/c system. Everything, coil, condensor, dryer and compressor, intact. I see the compressor is similar to what I have in Big Blue, which also is a 4.3. And similar to my old 95 Jimmy. And his was a 2001 Blazer. But I see something different with the wife's. All 3 of the others had the plug on the compressor directly behind the clutch. But the compressor in my wife's Saphire the plug is on the back of the unit. Anyone else have this. I even go on autozone and the one's they have for this model show the plug behind the clutch, not on the back. It's down underneath the air intake tube.

 

The plug behind the clutch energizes the electromagnet to engage the clutch. Depending on the compressor and/or system design, the sensor at the back of the compressor could be the system high pressure cutout switch.

 

That's what I was thinking but I can not find a plug behind the clutch...anywhere. not even the wiring for it....??? gonna look again. I just had it unbolted a couple weeks ago to replace a power steering hose. That's how I found that 1 plug in the back.

 

If wifes is still holding charge but compressor is not engaging could be low pressure switch has shut off compressor clutch.
This switch is located by aluminum dryer. Unplug it and take a paper clip is press into the wire connection and see if clutch will engage. If does than place your hand of suction side and see if it is cooling some. If there is some cooling than you need 134a. Mine turned out to have the o'rings leaking on the barrel of the compressor and would not hold a charge until the compressor was replaced. If you are going to replace with used compressor, carefully inspect the barrel of the compressor for signs of leakage. They are slide together with a large o'ring, old age and rust can cause them to fail; I am thinking that this is more common than a bad front seal.
Plug on back of compressor is a high pressure switch that cuts out compressor clutch when pressure is to high to protect your system.
L

 

Well I got in there last night (after the rains passed) and got with a flashlight. I could see the indent where the plug should be. Looked closer and sure enough in behind the clutch I can see where the wires have been cut. so the plug to the clutch has been broken off/removed. I still need to find the wiring side of the plug. but basically this compressor is dead. unless I can find a way to replace the clutch. Dunno on that one. But when checked the system is still holding charge so I know it's not leaking at least.

 

If you can see where the wires were cut; take a negative and positive wire from you battey (make test leads) and touch the two reminding what ever on the clutch and see if it works! If it does get out you solder gun and attach a new leads. Changing the clutch is not to hard; you can purchase a puller from Amazon, take the bolts off the compressor so you can get to the front. Also some of the part stores have tool loaning programs.

 

No go. It is broken off up under the back of the clutch. There is no way to get to the leads. BUT I do have a spare compressor off my son's other blazer that I can swap.

 

You stated that wife's car still was charged; I f you remove compressor and exchange will lose this charge and have to vacuum and refill. Why don't you just exchange the clutch off sons compressor to yours. Not a real big job and than you don't have to recharge and maybe the son's compressor is one where the seals are bad. Check you tube on how to do this job, I purchased the puller from Amazon.