A/C troubles, not easy to find fix.

[R Cashman]

Ok here I go.

07 gmc sierra classic hd 6.0L.

A/C clutch cycles on and off randomly and cannot duplicate. Here's what I've done.

Replaced: low and high side switches, relay, controler in dash, outside temp sensor, headliner temp sensor. The only thing I haven't replaced is the truck it self.

Pressures are within range when I've been able to keep the clutch engaged

It will not engage when jumping the low side. If I power the #87 pin in the fuse box (under the relay) the clutch will engage.

I've also adjusted the clutch air gap. Now at .025.

I cannot figure out where to look next. Or what to do. I really do not wont to run a new wire and toggle switch. 

 

Any suggestions. 

BTW. I'm fairly mechaniclly inclined (just replaced oil pump on the same truck w/o dropping front dif) but not up on technical verbiage so please dumb it down.

 

Edited April 21, 2020 by R Cashman
Forgot part of diag preformed

[swathdiver]

16 minutes ago, R Cashman said:

Ok here I go.

07 gmc sierra classic hd 6.0L.

A/C clutch cycles on and off randomly and cannot duplicate. Here's what I've done.

Replaced: low and high side switches, relay, controler in dash, outside temp sensor, headliner temp sensor. The only thing I haven't replaced is the truck it self.

Pressures are within range when I've been able to keep the clutch engaged

It will not engage when jumping the low side. If I power the #87 pin in the fuse box (under the relay) the clutch will engage.

I've also adjusted the clutch air gap. Now at .025.

I cannot figure out where to look next. Or what to do. I really do not wont to run a new wire and toggle switch. 

 

Any suggestions. 

BTW. I'm fairly mechaniclly inclined (just replaced oil pump on the same truck w/o dropping front dif) but not up on technical verbiage so please dumb it down.

 

There are AC specialists on here, I'm not one of them!  

[Formulabruce]

Did you know that the AC compressor clutch WILL cycle On and off when the Control inside is on ANY part of a "defrost" ??

 Yes it cycles in the winter too when defrost is selected, or partially selected.

 Maybe you do Not have an issue? 

Edited April 21, 2020 by Formulabruce

[R Cashman]

It does not cycle when defrost is on.

[Formulabruce]

Has to be the dash A/C switch, and, or, the air direction control switch on the dash. It should cycle on Defrost.

Power to #87 happens when pressure is satisfied and the A/C switch is on, or one of defrost positions is selected.

 make sure the controls are on outside air when you try a defrost mode.

 I am betting its in the dash. Good luck@!

[swathdiver]

If the computer detects anything amiss, there will be trouble codes for it stored in the Body Control Module/HVAC module.  You need an advanced scan tool to see these, like a Tech-2 or other bi-directional scan tool.