HVAC switch only working on high setting

[Doc Dave]

Sudden onset - lower settings blower not working at all, works fine on high.
2001 CTD truck, NV5600 transmission
Thanks

 

[BarryG]

Been a while since I dealt with that but am thinking you should check the blower motor resistor. It is down by the blower on the pass side. Two screws hold it in am thinking on the bottom of the blower box to left of the blower. Check to see if it is broken up into pieces or burnt to toast. High setting bypasses the resistor iirc. It will only take a few minutes to check. If it is that it will probably be obvious. I think genos garage still sells them for a reasonable price at least compared to the dealer if they even still sell them. Sometimes the blower motor is getting stiff from age and the bearings are not what they were 20 years ago. So if there is any squealing when you turn the fan on I would take a hard look at the blower motor as well causing to much elec draw and frying the resistor. On my previous 01 I went through three of them in the 18 years I had the truck and two blower motors (granted the replacements were the el cheapos from the cheap auto parts store but the dealer wanted $300 for the motor vs $65 from Advance Auto Parts) Easy peasy swap if needed.

 

[GAmes]

I get my blower motors from low mileage 2nd gens in the u-pull-it yards along with the resistors. A lot less cost that the parts house ones and they last much longer.

 

[BDaugherty]

Working on high only is typical blower motor speed resistor failure.

 

[KATOOM]

Its the blower motor resistor. Easy fix.

 

[B.G. Smith]

Had same problem, bought new resistor and when I removed the plug in to the resistor there was corrosion,,,,,,,, cleaned and still works great. Also still have the resistor I paid about $40.00 for in the tool box. Mine is 06.

 

[Joe Mc]

Yep what they said.

 

[mwilson]

The one thing I want to add after decades of selling resistors and heater motors for just about anything..

If the resistor is NOT corroded and shows signs of heat, missing resistor coils, etc. then do yourself a favor and change the blower motor out as well. Many times the resistor fails because the blower motor is drawing more amperage as it gets ready to cash out.....

 

[KATOOM]

Or...take the motor out and oil the bearings/bushings... They're only assembled with oil soaked pads which do dry out over time. I took mine out a few years ago and re-oiled the pads. Works as good as day one.

 

[Doc Dave]

Thanks to all for the good advice. I will check out the resistor first, then the blower motor, will try to lube it.

 

[Joe Mc]

RockAuto shows blower motors. I suggest getting one that already has with the squirrel cage.
https://www.rockauto.com/en/catalog...602,heat+&+air+conditioning,blower+motor,6916.
They also have the motor control module/resister
https://www.rockauto.com/en/catalog...g,blower+motor+control+module+/+resistor,6557