A/C Problem-2002 T.Blazer

[mpd13078]

Calling on all a/c pro's on this AWESOME forum. 2002 Trailblazer, 137k miles, I'm the second owner - purchased at 35k miles, kept all maintenance up. My a/c blows great cold air for 15-20 minutes on a humid day, then the LP switch dis-engages the clutch. (I tested the LP switch just to check it, jumper cuts off clutch). Warm air blows, the accumulator is hot to the touch so of course the air gets turned off. This system has never been opened, all original equipment.Research tells me that the evaporator is freezing because of course these conditions repeat itself. While the a/c is running normally, the evap. drain tube (is clean, I visually checked) is dripping water & the floor board/carpet has never been wet. I borrowed a manifold gauge set & all psi readings were good with the ambient temp. I change the air filter regularly, inspect air intake, clean throttle body...I'm on top of it all. I haven't visually inspected the evaporator from underneath the glove box panels yet. Idea's? Thanks in advance.

Mike

 

[gmcman]

So when you jump the LP switch, it turns off? Or does it turn back on?

Take a sprayer with cold water and mist it on the compressor after it shuts off, does it turn back on?

Could be the freon charge, hard to say without seeing the pressures. I had this same issue recently and it turned out my clutch was worn. I removed the shim behind the clutch and all is good again for now.....ymmv.

 

[Mooseman]

Or are you jumping the low pressure switch to force the compressor to run continuously? If that's the case, of course it will freeze because this is a cycling clutch orifice tube (CCOT) system and it must be allowed to cycle. Otherwise it will freeze.

As gmcman said, check the clutch. If the gap is excessive, it may not be re-engaging when it cycles off and it's hot. Shim removal could solve this.

 

[c good]

Weak clutch coil and/or excessive air gap as mentioned above.