AC Question--04 Silverado

[crroyalflush]

I have a 2004 Silverado LS w/ the 5.3. On occcasion the a/c will just stop blowing cold air. If I turn the truck off and back on then it starts blowing cold air again so I think its a switch, Im just not sure which one. Can anyone help?

[brcidd]

You (and we) need more hints.. Like does it do it when it is really humid?- or does the air flow quit, or does the the air just get hot? Is there a big puddle of condensate water under the truck when you shut it off? Is the compressor running when this happens? This would require stopping and crawling under the truck to see if clutch hub is turning- or at least feeling the low side pipes to see if they are warm, cold, or frosty?

Could be electrical, freeze-up, or something else at this point.

[j cAT]

Originally Posted by crroyalflush

I have a 2004 Silverado LS w/ the 5.3. On occcasion the a/c will just stop blowing cold air. If I turn the truck off and back on then it starts blowing cold air again so I think its a switch, Im just not sure which one. Can anyone help?

your cabin air filter may be plugged up...this is in the air duct under the dash next to the blower motor...this usually needs replacement often in dusty areas..replacement costs 20.oo...if you just discard this filter your evap will get plugged up ,and this will also give you your problem...perhaps this was already done..if so it will be pita.....

[jdmccright]

My guess is either a pressure or temperature cut-off switch. I would get an HVAC manifold gauge set and watch when it cuts out. Does the high side pressure get too high? Low side pressure too low? Typically they will cycle back on once pressures have returned to normal. I'd also feel the accumulator pipes for abnormal temperature. One should be cold and sweaty and the other hot, but neither to the extreme (icy/frosty and burning, respectively)

Is the AC air good and cold when it IS running? A vent thermometer should read abt 40-deg at max setting and HI fan speed at abt 1200 rpm.

Not sure abt the cabin filter since that would obstruct all air flow, not necessarily stop cold air from being produced, but the original poster is a bit vague in that. But I will say that if the evaporator gets too cold from lack of airflow it could trigger a low-temp cut-off switch.

[silicon212]

I'm going to take yet another approach. Under the dash on the passenger side is the resistor array. My friend Jim has an '06 Silverado, and his experienced exactly your problem. It was diagnosed as a bad resistor array, we replaced that (along with a replacement wire harness 'pigtail'), problem solved.

[crroyalflush]

I havent noticed any specific conditions that create the problem, ie, humidity etc. The air still blows but it just blows hot air. When the air is cold, it works great and is cold. I havent noticed any larger than usual puddles under the truck when its shut off and I havent noticed if the compressor is still running or not. It seems pretty random when it does it but when it does, it will do it several times in a day and then it wont do it again for a while.

[j cAT]

Originally Posted by crroyalflush

I havent noticed any specific conditions that create the problem, ie, humidity etc. The air still blows but it just blows hot air. When the air is cold, it works great and is cold. I havent noticed any larger than usual puddles under the truck when its shut off and I havent noticed if the compressor is still running or not. It seems pretty random when it does it but when it does, it will do it several times in a day and then it wont do it again for a while.

If the temp goes from cold to hot this may mean the temperature control motor is defective ..this is located directly above the hump in the floor under the dash...this is called a stepping motor..operates on 0-5volts dc

these have a good failure rate...