My blower motor for my climate control changes speed when I apply the brakes. I replaced the resistor thinking that was the most logical reason, well that wasn’t the case.
Blower motor isn’t making any funny noises and no other symptoms, other than increasing/decreasing speed when brakes are applied.

 

check the charging system/battery first. You should see 14v at the battery when the truck is running at idle. Blower motor is a high demand device, and may be showing you the first symptoms of possible problems.

Could be other stuff, but check the simple things first, look at serpentine belt condition, general wiring condition

 

Possible short circuit in the brake light system causing power drain when you hit the brakes...

 

leaning towards a short. blower wasn't doing nothing for a short period of time till I drove over some rail road tracks and it kicked back on. hunt it down tomorrow


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That sounds like a bad ground. Try running a ground wire from blower motor to frame or good ground point and see if that does any good.

 

I have to agree with a bad ground... You might even want to try grounding the TB as many of mentioned on here....