Question about Chevrolet Silverado 1500

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2004 silverado about twice this month the a/c decided to put out warm air as I was idling at a stop signafter a few seconds it would go back to cold air sisters car now doing the same on a tahoe

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  • Sterling Snyder Jun 25, 2009

    i got a lot more detail than I had hoped..hope it helps



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The evaporator cores on these vehicles are prone to leakage, and have been redesigned. They also have some pretty so[histicated electric controls that an AC tech can cheeck and calibrate for you. They have an evaporator temperature sensor that commonly fails, resulting in no compressor operation. The in car temp sensor located behind that little hole in the dash on the passenger side often blocks up with dust, changing system calibration.
It is absolutely critical that the charge of refrigereant be exact in newer cars; they don't hold nearly as much as older card sis; so a couple ounces off can can be 10% or more on some cars. There is no way to measure with any reliability from cans; a technician will use a digital scale accurate to within a half ounce or so when charging your system.
All air must be removed from an AC system, or it will not operate correctly. Air changes system pressures, and takes up space which refrigerant shuold be in. it also contains moisture, which causes corrosion and other internal damage. A tech will take a vacuumpump and remove all traces of air from an empty system before charging.
If the e=system is empty and contains air, the filter/drier must be replaced; it contains a dessicant bag that absorbs moisture to protect the system. if it is saturated, and the system is operating, it can rupture and spread debris throughout the system causing expensive damage.
Operating with a low refrigerant level WILL cause compressor damage eventually; the refrigerant carries oil for compressor lubrication. Running with low refrigerant before the system gets low enough to shut down is kind of like running your engine without oil; compressor failurte always results eventually. That is one reason exact charge level and finding & fixing small leaks is so important.
One last word of caution: NEVER put any type of sealer in an AC system. they do work sometimes, but are only for a car about to go to the scrapyard as a last resort. Once any type of sealer has been added to a system, it is basically unrepairable from that point on. It cannot be vacuumed for recharge, because sealers will destroy an AC service machine. AC techs routinely test for sealer in a system before begining repair for this reason. Sealers solidify upon contact with the moisture in air; therefore if the system runs completely empty or is opened to repalce a component, the sealer in the system solidifies everywhere , destroying the system. Avoid sealers at all costs!

or try this
my friend is answering you

It could also be the A/C compressor clutch or the pressure switch on the A/C line. Also, it could be the A/C switch on the panel inside the car. If the A/C clutch is not engaging, it can be tested by putting 12v on the plug going to the clutch. I made a test rig using a plug I got at Radio Shack. Just unplug the wiring harness to the A/C clutch ( on the compressor. Take the female side of the Radio shack Item 23-445, "9.6v Connector Repair Kit" and crimp in a wire to each of the leads about 3 ft long so it can be connected to the pos and neg battery terminals. You will have to cut the connector 'lock" of the plug so it will eaisly fit into the VW connector plug to the clutch. It is not an exact fit but you the can find a spot that will make contact and it the clutch works you will hear it click and then use a long pry bar and see if you can turn the clutch while it is engaged. if it is difficult to turn, then the clutch is working. The next most likely problem is the fan control module. I was able to get a VOM on the supply side of the A/C clutch to determine if there ws 12v going to the A/C clutch when the A/C was turned on. If no 12v, then it is more probable the fan control module is the problem, but there are other inputs to the fan control m odule; the A/C pressure switch (F129 or G65) the coolant temperature cut-out (F163) Ambient Air Temperature sensor. There is a procedure referenced on the forum somewhere on checking the Fan Control module using a VOM, but it looks like a pain in the ***. I am at the point where I know my A/C clutch is good, and I am not getting 12v out of the Fan Control Module, so my next step will be to replace the Fan Control module. I found one on UBID for $40 plus $13 shipping and fee. I am waiting for delivery.
-brother ray

Posted on Jun 25, 2009


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