Just stopped working one morning.

Clutch is not kicking on (was full of Freon). Replaced low pressure switch, high pressure switch, compressor relay, orifice, inside dash controller (with used one), Engine temperature sensor, and accumulator. Recharge unit. Still does not kick on. Bypass the compressor relay and unit runs fine. Lines sweats on suction side of orifice and hot on other side of orifice. Checked all fuses under hood and in cab. AC pressures are 35 on low side, 140 on high side (average) With compressor relay bypass. Tahoe calls for 2.5 lbs of freon, (i recharged with 38 ounces, Should be plenty to kick on) . Also notice engine cooling fan kicking on and off.

I just do not know what else to check/ replace. Compressor has to be good since unit runs fine with relay bypass.

 

i know the older models you could but can you bypass the pressure sensor and see if it still kick on?

 

yes did that and replaced both pressure switches. The high pressure switch, 3 prong, was bad (tested with my volt meter}. Still will not kick on. Something is telling the clutch not to engage. When old and now new relay is bypasses, everything works perfect. Bypasses at 2,000 rpm 35 on low and 150 on high

 

So you bypassed the low and high pressure switches and it still wouldn't kick on?

 

I did not bypass the HP sensor. I tested it with volt meter, it was bad so i replaced it. I replaced the LP sensor as well after I replaced the accumulator / dryer.. Then I bypassed the new LP sensor because replacing it did not repaid the problem. After bypassing the LP sensor, still did not fix the problem. I plug the LP sensor back into place, Bypasses the compressor relay and everything works. It cools like it suppose to and the clutch get power

 

so if the pressure switches are good i would think it was in the hvac switch. but this is just a guess

 

Wow - you "threw"/guessed with 7 different parts trying to "find one that stuck". Most of my AC experience is with "foreign" nameplate vehicles, but I think you would've come out ahead by taking this to a REAL auto AC shop (avoid ones like brake shops or quicky lubes that hang up a sign).


That should be plenty of R134a (not freon) to enable the AC clutch to engage, but high side pressure at about 1800 rpm is typically about 260 psi. I assume that you evacuated the system before introducing the R134a.

 

your on the right track.
I am wondering; maybe the grd control wire from the relay to the pcm is open....if you supply grd to the relay control side and everything runs...maybe a bad pcm, broken wire or inhibited.
the compressor relay is controlled by the pcm. not sure if 06 have this but 07 and newer would should if the a/c in inhibited due to a parameter data to the pcm….some examples would be...ambient temp, psi sensor input, ect etc.

 

Finally found the issue. Short in the wiring harness going to low pressure switch. I guess when I pulled it to check it, i was holding at a certain angle for the wires to make contact, then when plugged onto the switch it went to hell. Funny thing was, the very first thing i thought it was and replaced was the low pressure switch. Took a week to figure this one out. I would just get pissed and start driving my truck around till I cooled off and decided to give it another go.

As the above poster above said, would have been cheaper to take it to a mechanic. Well it is a man thing. Why spend $100 and let some one else fix it, when you can spend $500 and do it yourself. Also I am a gas compressor mechanic that works on 16 cylinder waukesha engines and solar turbines, There is no way i am going to let a little ac compressor eat my lunch.

 

Can the switch on the accumulator/dryer be replaced without losing freon? I have a slight leak and there is oil around that switch, which I'm assuming is the PAG oil (or whatever) from the a/c system.