QuestionI have a 2003 Silverado. When first started the ac blows cold, after 1-2 min it switches to hot. I located the rubber elbow drain on the firewall and inserted a plastic straw a few times, at least a quart of water drained out. I thought that may be it, but it still does the same thing. There was some water dripping from under dash before I cleared the drain. Is there a sensor that detects water accumulation and turns off ac function?
AnswerTom,
There is no sensor for water accumulation, that I have ever seen. But you should definately not have that much water there near your evaporator. You took the right first step by cleaning your drain hose. But if it was clooged that bad, I would dig further into it and see how much junk you have in the evaporator housing. It should be relatively clean.
My first thought is that with all of that water that had accumulated under the dash, there may be some moisture interfering with your blend door electrical connection. Your blend door is the door that seperates your heat from the heater core and the cool from your evaporator. Depending on what you set the dash control on depends on how it opens or closes. On many vehicles this is controlled by vaccuum lines. But on many newer vehicles they use electronics. Any moisture crossing the connections may send signals back to your control head to close the door. It's one possibility. If this is occurring, I recommend letting it dry out for a while, allow that moisture to evaporate off and see what happens.
If you ran it prior to this and it worked fine (recently,) and now it is allowing that much water to back up, that sends me in a new direction. It is very possible that your evaporator is freezing up on you, that could be the reason for the quart of water. The humidity in the air sticks to the evaporator as it absorbs heat. This usually just drains out the bottom of your vehicle. If your low side pressure drops below where it should, then that humidity is freezing on your evaporator and turning it into an ice block. Several things could be causing this one of course would be that you have a leak and have a low charge of refrigerant. Or you could have a restriction in your refrigerant line itself. Does your compressor remain running or does it cycle on and off? If you have access to a set of gauges and are able to send me your pressures and the temperature outside I will be able to tell more.
Thanks for your question and hope I helped a little.
