Blower problems (strange)

[av8r4aa]

My 635 just developed an odd blower problem.
The blower knob only controls 7/8 through max fan positions .

Does not matter where the knob is placed, the fan(s) fun at 7/8 power.
The knob can be at the lowest setting, yet still at 7/8 power.
You can go to max throw and it does go to override setting.
The CFM increases in override.

I think my blower switch is bad but never seen this before.

Does anyone have a used fan switch for sale or trade?

[Kennums]

Do you get the same symptoms with both the heater and a/c fans?

[av8r4aa]

Yes,
Same operation with AC .
The fan motor is unresponsive to the rotary dial.

[bimas]

My vote goes to the transistor inside the controller. I think it's a generic NPN transistor in a TO-220 size. BD543A is originally used but Radio Shack should have a replacement (under $2).

The variable resistor may also be worn inside the heat control dial. That one is specific to the car AFAIK.

[Taylor Marshall]

I'd be more inclined to believe that the in switch pot is pooched and not the in switch transistor. I do not think a transistor can partially fail (it works or it doesn't) but I can certainly see an old fashioned rotary potentiometer partially failing.
Greg,
I have an extra blower switch that I rebuilt (replaced the transistor) for the heck of it a couple of years ago. I checked the pot after the rebuild and it ohms out more or less in spec.
I don't mind mailing it to you but I never actually installed it into a car to be sure it functions properly in real life and I don't want to accept any payment for it unless I'm sure it works. You're an honest trustworthy dude and a long time inmate here so, if you like, I'll mail it to you and you let me know if it works or not. If it does, great, and we'll work out a reasonable deal on the shipping & price. If it doesn't then you can chuck it or cannabalize it as you see fit. Shipping surface mail won't cost me much so I'm not worried about getting that disbursement refunded if the switch is no good.
Taylor

[tkohl]

I'm having the same issue if there are anymore switches out there. Are there any other models that use the same blower switch?