So I’ve replaced the blower motor and blower motor resistor. My A/C clutch is good and I can feel cold air through the vents as I speed up. For some reason my fan is still not coming on speeds 1-4. I’ve already pulled the dash to start pulling the control unit. Does anyone have any troubleshooting ideas? Or am I just best off getting a new controller?

 

What year is the truck?

So the highest blower fan speed works but not the other speeds?


George

 

It’s a 2000 and no, no speeds work at all. I just know the condenser is good because it cools down when the clutch engages. I just can’t get the fan to turn on.

 

I am assuming manual AC because you said blower motor resistor.

Check the HVAC fuse 9 - 20A in the IP fuse block
Check the HVAC fuse - 30A under the hood

If no joy yet will it be easier to test the voltages at the blower resistor or the HVAC relay?


George

 

These are the controls I have. All fuses are good and have been replaced with fresh new ones. And both the resistor and relay are easy for me to get to. I’ve replaced both.

 

First make sure that you have 12v coming into the controls on the brown wire at the control Head connector. There are three brown wires. Two are power out to the resistor bridge and the third is the one we want, it is power from the HVAC9 fuse.

Then with the mode switch on anything but off and the fan speed on med 1 (the second fan speed), is there power on the tan wire from the control head to the resistor bridge?

with fan on high is there 12v on pin 86 in the blower motor relay socket or alternately on the associated orange wire from the control head to the blower motor relay socket?


George

 

I am assuming this is the control head connector and when I am measuring for DC voltage my readings are all over the place and never get 12v

 

Testing my volt meter, I believe it has taken a crap on me. Hooking up to the battery I only momentarily saw a 14v reading so if possible do you have any ideas how to trouble shoot without a volt meter?

 

Do you have a test light/probe?


George

 

Grabbing one right now. Could you clarify the connections I should be looking at? I’ve found multiple brown wires in different locations and I’m not sure what the 86pin is. I really appreciate your time!