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Silverado - Blower Motor Runs After Engine Is Shut Off

stampeder

By stampeder
in Ask A GM Technician

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stampeder Enthusiast

stampeder

Posted
Posted

2000 Chevrolet Silverado 2500 4WD

 

Found the battery dead the other morning, discovered the blower fan had come on in the night when the truck was shut off.

 

Disconnected the blower at the resistor so I could have my truck back. Conventional wisdom on the boards says this problem could be caused by a faulty relay. I swapped out the Air Conditioning relay under the hood with no change.

 

Could this problem be caused by the Blower Motor Resistor? I have read in another thread on this board that resistors are a common problem, but they are usually associated with fan speed problems.

 

The truck and I are currently in Mexico for the winter, so I will likely have to import the part from the US, so I would like to be sure before I order any parts.

 

Thank you

Rob (from Calgary, currently in Puerto Morelos...near Cancun)

Fortune50 Enthusiast

Fortune50

Posted
Posted

The blower motor resistor module has the blower relay built into it and it could stick as it does have power to it all the time from the FRT HVAC fuse.

Test to see if you have a faulty ignition switch, turn OFF the ignition switch and test for power at the HTR-A/C fuse which supplies the power to the HVAC controller's fan switch. If there's power, there's either a short to positive in that circuit, or the ignition switch is faulty.

If no power at that fuse w/ the keyswitch OFF, then there shouldn't be any power reaching the fan switch to power the blower resistor/relay in the low speed settings. Anyway, to test to see if power is coming from the HVAC controller's fan switch, test w/ the ignition switch in the OFF position and test for power (connect one test light or DMM lead to terminal, the other lead to ground) at these wires at the resistor/relay harness: yellow, tan, light blue, purple, & the correct orange wire. There will be two orange wires, one will ALWAYS have power straight from the FRT HVAC fuse, the other will be from the HVAC controller's fan switch and will only have power when the fan is set to high and the ignition keyswitch is turned to ON. If you want to find the correct one which comes from the HVAC controller, you can test the orange wire which has power, then pull that FRT HVAC fuse and see if it lost power, if so, then you know you have to test the other orange wire. If everything is testing ok, then you could probably assume the resistor/relay module is faulty. Good luck to you!

Here's a schematic, sorry if it's pretty crappy, cheap cellphone, lol. The upper right is the FRT HVAC fuse which is always hot, the upper left is the HTR-A/C fuse which is only hot w/ the keyswitch in RUN.

GMtruckblowermotorresistor.jpg

stampeder Enthusiast

stampeder

Posted
  • Author
Posted

Hola Fortune50,

 

I did those tests and everything was exactly as you said. Looks like I have a faulty resistor/relay.

 

Many thanks!

Rob

stampeder Enthusiast

stampeder

Posted
  • Author
Posted

Just a follow up here. I was able to obtain a new blower motor resistor/relay here at the GM dealer in Cancun, a miracle to say the least! The part number has changed again, it is now 89019089. They had exactly one in stock.

 

It looks quite a bit different, so hopefully it is a little hardier than the old design. In any case, it fit and it worked. Solved my problem completely. (Driving a truck on a highway in Mexico without moving air is not exactly fun)

 

My thanks to Fortune50 and this board for helping me out. This board is a precious resource!

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