'98 Tahoe AC does not turn on

[Flamingdeath]

I have a '98 Tahoe that I have been trying to get to work consistently for a year now. First, the compressor was not cooling, so I had the AC looked at by a shop and they replaced the compressor(supposedly flushed out the sytem as well to clear any debris), charged the system and it worked, for about 4 months.
Then it all of a sudden would not turn on at all when I hit the AC button. There is no engagement of the compressor (no clicking sounds or nothing). I have checkked the fuses in the dash and in the engine compartment. I tested the voltage in the wires at the ocmpressor and there is no voltage there at all.
This is where I stopped. Does anyone have any ideas? I am pretty versitile with a multimeter. Thank you in advance for your time and help with this.

Rodney

[brcidd]

65% of mobile a/c failures are due to loss of refrigerant due to a leak. Does your Tahoe have rear air? If so, rear lines are highly suspect- look for oily/greasy residue at any and all grommets- very common leak area-- also compressor body/belly leakers are common, but primarily with OEM units, not replacement units. What you need to do is measure the system static pressure with an a/c pressure gauge-- if less than 47 psi, you have lost 95% of your refrigerant....and compressor has been disabled for that reason.

[Flamingdeath]

Thnx brcidd,

I was thinking it was an electrical issue with the on/off portion of the AC switching. So if there is a leak, the computer will shut down the compressor automatically if the pressure is not up to where it needs to be? I just want to understand, oh, and yes, I do have rear AC. Where is this notorious bad junction area located? I would like to check it out as well to be sure (this baby has 304K on her).

[777stickman]

Look in the underhood fuse center. There maybe an "a/c compressor clutch relay".

[j cAT]

Originally Posted by Flamingdeath

Thnx brcidd,

I was thinking it was an electrical issue with the on/off portion of the AC switching. So if there is a leak, the computer will shut down the compressor automatically if the pressure is not up to where it needs to be? I just want to understand, oh, and yes, I do have rear AC. Where is this notorious bad junction area located? I would like to check it out as well to be sure (this baby has 304K on her).

the low pressure switch is at the under hood passenger side refrigerant filter dryer. has 2 wires see if voltage is on both or one wire.if no voltage could be fuses/relays. if its on one jump the switch for a quick 2 sec. see if compressor clutch cuts on turns on if so next step is to measure the pressure at the test port there.if its below 10psi that is why it is not turning on ... if it was fully charged it would be over 100 psi . ac compressor not running.. normal running in warm weather it should read 40-45 psi .. so my recommendation is bring it back if it is with no refrigerant because they screwed up ! they may have not used NEW O rings/SEALS.......... or the compressor seals are defective that would be expensive.

[Flamingdeath]

Thanks to both of you. I will do all those checks and go from there. Thank you again for the suggestions.