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99 Yukon AC issue

coachdubya

By coachdubya
in Ask A GM Technician

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coachdubya Enthusiast

coachdubya

Posted
Posted

So had to turn the AC on the other day(TX winter ya know) and no cold air, just blows warm......well, d**n. Compressor is not engaging.

 

Checked fuses.....everything looks ok

A/C Relay seems to work fine.....(switched it with starter relay since they are the same)

Unplugged and put a meter on the wiring harness at compressor......no juice.....

 

Ah.....thankfully a clue, but what next?

skills4lou Enthusiast

skills4lou

Posted
Posted

It's entirely possible the R134 just needs to be recharged. There's a pressure switch that won't allow the compressor to run if the low side doesn't have enough pressure. Most of time that's caused by not enough refridgerant (R134). You can either buy the recharge bottles at the parts store or spend the $50 and have a shop do it. Hope that helps

coachdubya Enthusiast

coachdubya

Posted
  • Author
Posted
It's entirely possible the R134 just needs to be recharged. There's a pressure switch that won't allow the compressor to run if the low side doesn't have enough pressure. Most of time that's caused by not enough refridgerant (R134). You can either buy the recharge bottles at the parts store or spend the $50 and have a shop do it. Hope that helps

 

 

 

 

Thanks for taking the time to respond. System is charged.

 

Read something on another post about a low pressure switch @ the accumulator/dryer......if that switch is faulty would that kill the juice? If so maybe that's the culprit.

  • 4 weeks later...
ChevyTech007 Enthusiast

ChevyTech007

Posted
Posted

Hard to say because it depends on outside temp, blower speed and many other variables, but should be around 40 on the low side and 200 on the high side. Did you put a cycling switch on it?

coachdubya Enthusiast

coachdubya

Posted
  • Author
Posted
Hard to say because it depends on outside temp, blower speed and many other variables, but should be around 40 on the low side and 200 on the high side. Did you put a cycling switch on it?

 

 

 

 

Not yet. Weather has been fairly decent so put it off.

 

Decided to take a look at it again today. Removed the plug from the cycling switch and jumped it.......compressor kicked on. For what little I know, seems like that confirms switch is bad. However there may be another issue. Low side pressure is ok, but high side pressure doesn't seem to be increasing if you cycle compressor on (via jumping) for a few secs at a time.

 

Shouldn't pressure increase on high side when compressor engages?

  • 2 years later...
yukonsurf New Member

yukonsurf

Posted
Posted

when you guys say "jump" the switch, do you mean complete the circuit? I have had an issue with the a/c staying cold. It takes a while to get cold ,sometime 15 minutes and then the cool air goes away and gets humid.

 

refrigerant is charged up to stats, and rerecently replaced the low pressure cycling switch but still have the same problem. Maybe if GM had a bad batch possibly I bought a bad new one from the dealer. So I wanted to bypass the swith to see if the compressor kicks in. I 've heard to use a jumper but not completely sure how to jump the switch to check if in fact I have another bad switch or if it is something else. 04 GMC yukon

billydaniel New Member

billydaniel

Posted
Posted

How do I jump the switch on the compressor to get it running so I can add freon?

 

 

Hard to say because it depends on outside temp, blower speed and many other variables, but should be around 40 on the low side and 200 on the high side. Did you put a cycling switch on it?

 

 

 

 

Not yet. Weather has been fairly decent so put it off.

 

Decided to take a look at it again today. Removed the plug from the cycling switch and jumped it.......compressor kicked on. For what little I know, seems like that confirms switch is bad. However there may be another issue. Low side pressure is ok, but high side pressure doesn't seem to be increasing if you cycle compressor on (via jumping) for a few secs at a time.

 

Shouldn't pressure increase on high side when compressor engages?

 

 

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