I'm new to the forum so I hope I'm posting this correctly...I have a 2000 Blazer LS with V6. My current problem is with the AC. The compressor won't engage. I changed the compressor and while changing, found the connector on liquid lines was broken. I changed the lines and pulled a good vacuum on the entire system. I added R134A while watching the suction pressure. The compressor would not engage so the pressure was equalized and read about 90 psi. I tried jumping the pressure switch but no luck. Checked at electrical connector on the compressor but no 12V power. I jumped power to the compressor and it engaged and started cooling. With power jumped to the compressor I finished charging the system...40 psi on the low side at 90 deg ambient temp. I checked HVAC fuses in both fuse blocks and HVAC relay in the fuse block under the hood. These are all good. From what I've read on the forum, I suspect the control panel could be the problem. I understand there are vacuum lines on this panel. Would a vacuum problem prevent the compressor from engaging or is this strictly an electrical issue? Is there anything else that could cause this problem. Any help would be greatly appreciated...it's hot in South Texas.

 

Vacuum will not inhibit the clutch. Manual AC or climate control? Either way, the PCM ultimately controls the clutch. Did you check the, (normally closed) high pressure cut-out switch on the rear of the compressor?

 

Yes. High pressure switch is ok too. If I understand some of the previous posts, it's manual...there are no numbers on the temp control only red and blue lines. Is the PCM the main computer under the hood or is that the control panel for the HVAC?

 

No numbers = manual A/C. PCM is mounted on top of the radiator overflow reservoir, on the right inner fender. The body control module also plays a part in clutch activation and it's located under the dash, driver side just above the tunnel. I'll check the schematic and post some things to check, (tomorrow).

 

Thanks...appreciate the help!

 

Turn on PM.

 

PM is turned on in the User Control Panel. I can't PM until I've been a member of the forum for 2 days. I just joined yesterday.

 

Have you checked both terminals on each fuse, in both fuse panels, with the ignition in the RUN position?

EDIT: I have a schematic for your vehicle and can walk you through component, wiring, and voltage tests if necessary.

 

First of all, thanks to Captain Hook for all the help and guidance in tracking down the problem and thanks to Blazer Forum for providing a great place to connect with knowledgeable Blazer folks.

My problem turned out to be a blown 10 amp fuse labeled "AC" which is located in the fuse block under the hood. I thought I had checked all the A/C related fuses but without a schematic, all I had to go on was the map located under the fuse block cover. Unfortunately, the label for this particular fuse had a wide black mark that made it completely un readable. It appears that over the years the cover rubbed on components underneath to mark out the label for only this fuse.

For anyone having a similar problem with their A/C compressor, I would offer the following information:

In addition to the HVAC fuses located in both the dash and under hood fuse blocks, there are 2 fuses that are key to operation of the A/C compressor clutch. One is a 10 amp fuse labeled "IGN E". This fuse supplies power to the A/C Compressor Clutch Relay coil. The PCM cannot energize this relay if this fuse is blown. The second is a 10 amp fuse labeled "AC". This fuse supplies power through the A/C Compressor Clutch Relay contacts to engage the compressor clutch. Either of these fuses will prevent the compressor from coming on.

 

Bingo! Good job, glad you found it. Thanks for posting back with the fix.