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2013 Sierra Rising Temp Gauge No AC and No highspeed fan

Michael Lauze




I have a 2013 GMC Sierra Nevada 4.8. I live in Manitoba Canada where for 10 months out of the year it is below freezing! Last week we had a warm day so while my wife was shopping I decided to turn on the AC while I was waiting for her, I got the 3 flash light and it went off, I thought it was because it was to cool still. Than I noticed me temp gauge start to rise. I have owned this truck since it was new and pull a small 5th wheel around with it I have never seen the temp gauge move before. So I sat there waiting to here the fan kick on... It never did, slowly the temp went back down, but within 15 minutes it was back up again. I'm wondering is it possible that a fan relay could be gone and that is why the highspeed fan never kicked in as well as why the AC won't work.


I also tried it yesterday and had the same problem.... I'm stumped!

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Is the compressor engaging? If it is not engaging, then the cooling fan will not come on until the engine temp requires it. Because there are actually two completely different fan systems involved, one for the cooling system/condenser and one for the cabin air circulation, it is important to specify which one you are referring to when you say "highspeed fan".


You can "estimate" the refrigerant level by feeling the temp on both lines at the condenser, as well as both lines at the heater box. Small line at heater box should be hot, then cold right after the fixed orifice tube crimp on the small line. The large line coming out of the heater box should be cold. If the temps are the same at the heater box, then the compressor is not likely running. This can be due to low level. The two lines at the condenser should be both hot. The outlet side may feel slightly cooler, but not much. Main function of the condenser is to change the high side from hot gas to hot liquid.

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