97 gmc seirra 2500

[birchhatchery]

on my truck it will blow heat in all setting just the same as if having the vent on but it will only blow faster if its on high what could cause this bad switch?

 

[RHamill]

Sounds like it could be your HVAC controls, remove then and inspect the connector, mine burned and melted black plastic into back of knob causing a bunch of problems like that.

 

[badazzbulldog]

resistor at the blower motor below the glovebox

 

[gmcyukondriver]

resistor at the blower motor below the glovebox

All the lower fan speeds get powered through this resistor. "Hi" doesn't use the resistor, essentially full power to the blower motor. If your high is good, but lower speeds aren't, it's most likely the resistor.

 

[great white]

All the lower fan speeds get powered through this resistor. "Hi" doesn't use the resistor, essentially full power to the blower motor. If your high is good, but lower speeds aren't, it's most likely the resistor.

By the OP description, I concur.

Resistor is gone bad or potentially the connector has melted on the resistor (it happens sometimes):

http://www.youtube.com/watch?v=SDk3UaWeC9Q

FF to 2:27 for the resistor.

 

[birchhatchery]

also when I run the heat on the high the truck has a smell of antifreeze but I don't have any leaking down the firewall from the heater core onto the floor of the cab. is this a type of heater core that it will just puddle up and not leak out or will it leak? or maybe its just the smell of the truck as I have not owned it long

 

[birchhatchery]

anyone

 

[birchhatchery]

and I also check the anti freeze in the radiator its been the same level for days