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Blower Fan Stuck on High - HVAC Controls Dead

Posted: Thu Jul 07, 2016 6:09 pm
by GFremont
I started having issues with my HVAC controls and blower fans the other day. They were working normal and then the front and rear fans shot to HIGH, the HVAC controls went dead, and all the HVAC indicators on the screen disappeared. The truck is equipped with the Automatic blower/fan option.

Here is the link to the YouTube video:

https://youtu.be/n4xyhqc-TNI

The noise in the background are the fans running on HIGH.

The CANBUS diagnostic has the Rx(HVAC) Status as UNKWN

Any suggestions would be appreciated.

Posted: Thu Jul 07, 2016 6:21 pm
by smj999smj
Fans on high speed is a default mode; it's better to have fans on high all the time than no fans at any time. Hopefully, the HVAC control head didn't bite the dust. I would start by checking your fuses and fusible links. If those are okay, then you'll have to refer to the symptom chart in the factory service manual to get the appropriate diagnostic procedure.

Posted: Thu Jul 07, 2016 6:33 pm
by GFremont
smj999smj wrote:Fans on high speed is a default mode; it's better to have fans on high all the time than no fans at any time. Hopefully, the HVAC control head didn't bite the dust. I would start by checking your fuses and fusible links. If those are okay, then you'll have to refer to the symptom chart in the factory service manual to get the appropriate diagnostic procedure.
I'm working that now. I replaced the Variable Blower Control but that wasn't it. Fortunately I was able to take it back for a refund.

Posted: Fri Jul 08, 2016 4:45 pm
by Kael2001
I think the 2008 still had the self diagnosis mode built in.. Try going to the 'secret' stereo menu by pressing and holding the Setting button then rotating the volume knob till the menu pops up (usually 40 clicks just go crazy lol)

It should then have an option for confirmation/adjustment.
Click on it and go to climate control. It should run a self diagnostic check and show any error codes in the ambient temperature screen bit.

If you post the codes I'll tell you what the book says lol.

If there isn't the option no harm done!