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High Only Blower Motor

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I posted in that one thread, but I never fix stuff unless the truck wont run it seems.. I still have just high setting, so if it gives you any peace of mind that it wont go out until you getter fixed :)
 
I had one of my switches start smoking once. That incident has encouraged me to keep a small fire extinguisher in all our vehicles now - within handy reach of the driver. (wifes is on the center hump - havent decided where mine shall live in the burb yet)
 
ak diesel driver said:
on mine the diode was blown (part of the resistor)
Click to expand...

If the motor stops spinning the 'diode' looking thing blows. It is actually a Thermal fuse. This prevents a locked up blower motor from burning the truck down as the air cooled resistors would overheat and melt otherwise.

I illustrate how to test the resistor pack. Circle is the tester and the line are the test leads. Test the fuses first and the resistor wire coils next. They should all have a reading. An open means the resistors or fuses have quit.

You need to find out why before you replace it. Loose wire, failing blower motor... Because if the motor stops the fuses will burn out again.

Fuse test:

test fuse.jpg

Resistor wire test, coils:

resistor test.jpg
 
What year was that off of? I'm pretty sure my 96 only had 1 diode/fuse and I had high only. It went out all at once when I turned the fan off quickly while waiting for the glows. I might have saved it I'll have to take a look tomorrow.
 
It went out all at once when I turned the fan off quickly while waiting for the glows. I might have saved it I'll have to take a look tomorrow.
Click to expand...

So if your fan is on while the glow cycle is operating, you blow your climate control switch......funny thing cause I have a "BRAND NEW" head control and the 2nd speed mysteriously stopped working....and I did shut it off while attempting a ice cold first start of the day, which I needed to jump/boost and tighten up a driver side ground cable on the batt.....HMMMMM?????
 
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You can see the actual "Blown" Diode and know which speed isn't working??

Yea I've changed a few in my rigs lifetime....Thanks for the info AK


Louis
 
So where exactly is this resistor block? Get at from below? Remove dash faces?

From that diagram it appeared to be at the top of the dash?
 
Shown is the 1993 resistor pack. Testing is the same for newer model units with more speeds - 4 resistor coils and the different design of only 1 Thermal fuse. Good pic to post, AK.

No you can't tell by looking at them as corrosion makes it look bad but it is good.

1993 is behind glove box and a relay pack on top of the HVAC unit. The bolts require a wrench and time to get the stubborn tight fit one out.

As the other threads show check the main HVAC power connector for melting and add a extra ground to the blower motor.
 
Perhaps it would just be easier to mount a better type aftermarket resistor 12v switch? Knob perhaps.??

Think it takes more than 20a?
 
Matt Bachand said:
Perhaps it would just be easier to mount a better type aftermarket resistor 12v switch? Knob perhaps.??

Think it takes more than 20a?
Click to expand...

you need to use the factory type, the air flow (hot or cold) cools the resistor for the fan speed, one of the knob type (dimmer switch) would overheat and fail or burn.
 
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