Re: 1999 Blazer 4 dr 4.3 2wd

This is almost funny, just replaced the fuel pump and took the Blazer for a test drive. Everything worked (fuel pump and a/c). On the way back from the store, the a/c stopped working, the clutch was not engaging. It is was 103 degrees yesterday and not a welcome discovery.

I read up on some of the postings here and thought that I may need to put more R-134a into the system even though my air is quite cool when it works properly. Even so,I figured I would go to the store on Sunday and get a can and a guage to test.

First thing in the morning, before driving off to the parts store,I checked the a/c and it worked just fine. Figuring that I may just be on the border of lower pressure, I went ahead and purchased a can of R-134a with a gauge on it.

I put the gauge on and it turns out that I am on the high side of normal and do not need any more.

Any suggestions? I guess it is possible that my pressure switch is going bad? I guessI should test it out the next time it stops working, assuming it stops working again. Any suggestions on what to check besides the switch and relay?

 

Took truck out today and the same thing happened. Going to the store, the a/c worked just fine. Coming home, the a/c stopped. When I got home, I swapped the relays and the clutch still did not engage. I assume the relay is ok.

Removed the leads from the pressure switch and then put it back on and the clutch momentarily engaged but then stopped. I did it one more time and the clutch remained engaged. Could be the switch or just a poor condition.

If this happens again, what should I measure at the pins of the switch? Is that pressure switch either on or off or is it variable? I am going to assume the switch is normally closed but will open if the pressure drops.

If I attempt to replace the switch, I assume I will lose my freon, right?

 

I believe there is a check valve in the low pressure / cycling switch (located on the passenger side of the engine on the refridgerant line). Replacement procedures in my references do not mention recovery of any refridgerant like the high pressure switch replacement does. You will want to lubricate the new o-ring that should come with the replacement sensor with some 525 viscosity refridgerant oil, but try not to get any of the oil onto the end of the sensor or in the refridgerant lines.

 

Mine was doing this as well, checked the level and pressure was fine, I pulled the plug from the condenser and tapped it with a wire to close the circuit like swartlkk suggested in a past postand it didn't happen again. Try that as a test to prove that it is the switch.