Suburban Heater AC Fan Won't Shut Fff?

Last post on Oct 24, 2009 at 7:22 PM

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#1 of 1 2005 Suburban heater/ac fan won't shut off? by myze Oct 24, 2009 (7:22 pm)
I am fixing up a 2005 Chevy Suburban that was laid over on it left side. I have all the body work completed but when I connect the battery cable the front compartment interior fan comes on high speed. The fan runs wide open & the speed cannot be controlled by the fan speed knob, even though the light bar shows increasing & decreasing bars. The rest of the heater/ac position & temperatture controls work fine. What is really weird is that the fan runs even when the ignition switch is turned off. The only way to stop it is to disconnect the battery or pull the fan fuse. The rear heater/ac fan speed, discharge position, & temperature controls work fine as well. My first thought was that the fan speed control switch was bad, but that doesn't explain why the fan would continue to run even when the ignition switch is turned off. My next thought was that there must power supply relay to the fan is stuck closed. I checked every relay in all of the fuse boxes, but couldn't find anything that appears to control the fan. Also if it was a stuck relay, it doesn't explain why the speed control doesn't work? I removed the kick panel on the P.S. & there is some sort of control board between the fan & the supply harness. I was hoping somebody could point me in the right direction, so I don't end up buying expensive circuit boards that won't fix the problem...

#1 of 1: 2005 Suburban heater/ac fan won't shut off? by myze; Oct 24, 2009 (7:22 pm)

I am fixing up a 2005 Chevy Suburban that was laid over on it left side. I have all the body work completed but when I connect the battery cable the front compartment interior fan comes on high speed. The fan runs wide open & the speed cannot be controlled by the fan speed knob, even though the light bar shows increasing & decreasing bars. The rest of the heater/ac position & temperatture controls work fine. What is really weird is that the fan runs even when the ignition switch is turned off. The only way to stop it is to disconnect the battery or pull the fan fuse. The rear heater/ac fan speed, discharge position, & temperature controls work fine as well.

My first thought was that the fan speed control switch was bad, but that doesn't explain why the fan would continue to run even when the ignition switch is turned off. My next thought was that there must power supply relay to the fan is stuck closed. I checked every relay in all of the fuse boxes, but couldn't find anything that appears to control the fan. Also if it was a stuck relay, it doesn't explain why the speed control doesn't work? I removed the kick panel on the P.S. & there is some sort of control board between the fan & the supply harness. I was hoping somebody could point me in the right direction, so I don't end up buying expensive circuit boards that won't fix the problem...