Blower Relay?

keepontruckin

Original poster
Member
Dec 5, 2011
82
Hey everyone,

My heat/AC blower does not seem to blow as hard as it used to, once halfway up or so it stays about the same speed...where is the relay for the blower motor? I'm assuming this is the problem since it works just not as well.

Any help is appreciated,

Thanks,
Rob
 

willn513

Member
Dec 4, 2011
918
Take the glovebox out and you'll see it right there. Assuming you have the manual controls it's a simple fix. Not sure about the digital controls though. Do a search on here for blower motor resistor and you'll find what you need.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR

keepontruckin

Original poster
Member
Dec 5, 2011
82
thanks guys, sorry about the late reply...

I have the automatic/digital display, and I do have a voltmeter...If its not the blower motor, then its the blower motor resistor right? and im assuming with the digital display its a more complicated fix?

-Rob
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
The digital system has a more expensive speed control module, but it's located in the same place near the blower motor. And fewer wires go to it, but they can still overheat and melt the connector body. Look at it closely first, and you can decide if you need the wiring pigtail to repair it or just the module. You could use the voltmeter to check out the input voltage to the module (on a 3-pin harness), the output to the blower, and also (put on the AC range) the control line to the FET module, which is the skinniest wire of the three. It's a PWM signal if you have any engineering background.

It's controlled by a FET (field effect transistor) inside the module, more like a room light dimmer with smoothly variable speeds. The lower-end manual control with five discrete speeds uses the cheaper resistor design to slow down the motor. Both units need to be placed in the airflow of the blower, because the airflow is needed to cool off the heat sink (for the FET) or the resistors themselves. But the engineers always have a challenge because the way the resistors work is that whatever energy doesn't go into the blower needs to be thrown away (dissipated) in the resistor. The slowest speed has the highest need to discarb unwanted power. But that's ALSO the speed with the least airflow. The problem is sort of obvious.

Here's the thread for the digital unit:

http://gmtnation.com/f23/possible-control-module-problem-blower-motor-wont-turn-off-1440/
 

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