No Low/mid Speed On Heater Blower Motor

[roberth]

Hi folks, can anyone tell me where the Blower Relay is on the 1991 GMC K1500 p/u model? I lost the low and mid speeds...only have the high speed. Got the new Blower Relay ,but it is not where I thought i t was. Any knowledge of where to find it is greatly appreciated.

 

Could not find anything in the Haynes Manuals on it.

[rodram]

.... it should be behind the glove box (unless the '91s are different somehow) ... pull the glove box right out as far as possible and it should be on a harness up behind the dash.. reach in a pull out whatever harness is flexible enough the come out

[roberth]

Thanks Rod....I found it behind the glove box. A cluster of 3 relays are in a row attached to a bracket held down by 2 screws. It was the far left relay. I changed it with the new one. Didn't fix the issue. I could hear and feel the clicking in the reley as I changed the speeds on the switch from low to medium to high. The blower only runs on High Speed? If it is not the relay, it is possible the blower motor is bad? Assuming the motor has some type of control for handling variable inputs to control the speed. If not, what else could it be? I would not think the switch could be an issue if the relay is clicking and the new relay was no different.

[rodram]

.. when I had my blower motor replaced last fall, my mechanic said that if it was dead at all switch speeds, then it is most likely the blower motor (which it was in my case..)

 

.. he also said that when only high speed works then it is most likely the blower resistor that is gone .... now you are talking about a relay... while I understand it is a resistor that causes this problem... check to see if you have any other part on that harness that looks like it might be fried ... if so, then that is your blown resistor...

 

.. very seldom is it the switch causing the problem

[matt76]

i have had to replace the heat\ac control assembly twice now on my 98. the first time i lost control of fan speeds, pulled the unit from the dash and noticed the wire harness for the fan control had melted. bought a new one for $150 bucks and four years later the same thing has happened. melted wire harness. you can buy just the blower control switch for $20 at auto zone instead of buying the whole control assembly for 150.

[grosss]

Relays are different from resistors... you wouldn't find the blower motor resistor making noise or vibrations no matter what you do on the dial, and it's a common failure for the resistor to go. The resistor (if it's similar to the 99+ style) will look more like a circuit board sticking out of a plastic box... and it's quite obvious when it's fried. do a search on the internet for the part to find a picture of it.