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Old 08-07-2017, 04:04 PM
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HVAC Controls Acting Up

Hey everyone! I am starting to run out of ideas for fixing my HVAC.

A little background: About a month ago I attempted to use the heat in my 15 JKUR (out of warranty - I drive a lot) and I would only get cold air. AC worked fine when I manually selected it but the blend door wouldn't move when switched to heat. So after doing some research I found out how to get at the blend door motor and replaced it. You can imagine my elation when the motor took off after getting it hooked up. Unfortunately the whole system would calibrate every key cycle.

A little more research and I figured I may have a problem with the head control unit and went about replacing that. Easy enough, order online - install and keep my fingers crossed... unfortunately it still does this calibration on every key cycle. The rear defrost light blinks until it does its thing and then I have functionality again.

One thing I have noticed though is that while I have cold air all the way on cold and hot air all the way on hot, I don't seem to have much in the way of temp control in the middle. I used to be able to set it to 70 and have a nice even temperature whereas now it does not work that way.

My guesses are possibly a bad ground in the system somewhere or possibly the temp sensor is on the fritz.

My question is has anyone had this issue and fixed it themselves. I'd rather not go to the dealer at any cost. I've read some older threads and one or two did mention a faulty ground. Does anyone have the wiring diagram for the HVAC system? Or does anyone have any other ideas I could try?

Sorry for the long post but I didn't want to leave out what I've already tried.

Thanks everyone.

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Old 08-07-2017, 05:42 PM   #2
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The dealer can hook up the SCAN tool to the OBD reader and read the HVAC errors. Some times it is the HVAC control module, and some times it is the blend door actuators or the motor for them.

Dealer is the only way to get them to read the fault codes...

See this...it's my post there - and the HVAC module replacement fixed mine, but only because I had no errors...

Rear Defrost Light Blinking On Startup - JeepForum.com

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Old 08-09-2017, 07:15 AM   #3
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This just started happening on mine on monday, the day you posted this topic. I'll have to get the codes read. Cant a place like advanced auto read the code for free? Or is it a special reader to get HVAC codes?
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Old 08-10-2017, 07:32 AM
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I don't think the HVAC specific codes will come up unless you have the StarScan thing. I could be wrong though. Are you still under warranty? If so and you do end up at the dealership let us know what they do.
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Old 08-10-2017, 08:43 AM   #5
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Quote:
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I don't think the HVAC specific codes will come up unless you have the StarScan thing. I could be wrong though. Are you still under warranty? If so and you do end up at the dealership let us know what they do.
Correct - you need the StarScan tool to read the fault.
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