Fan Switch not working well

[VairKing]

Hey guys:
The fan switch for the heater/ac blower on my 91 is having issues. It only works on full. If its on any position other than full, it is off. Is it a bad switch or what? Any suggestions welcome...TIA

 

[Kadarom Douhrek]

Somehow mine lost High.
Works on Low, Med and Max but no High.
Haven't bothered to look into it yet though since good ol' Texas wheather means it's usually set to Max-Heat or Max-Cool.

 

[VairKing]

TTT anybody else have any ideas?

 

[Howard]

It sounds like the resistor is blown. Its next to the fan under the hood. ( the resistor is bypassed for full power)
Hope this helps.

 

[Eddie X]

Blower resistor. Cheap part, hard to get to, and don't bother with parts stores 'cause they are only available at Ford.

 

[CHH777]

My fan only works when it wants to. It works at all speeds or doesn't work at all...

 

[Opera House]

In the resistor assembly

There is a thermal fuse, same as in hair dryers and coffee pots, that is chemical and burns opens at a certain temperature. It looks kike a metal diode. Function is to shut off current if air flow is restricted and resistors could cause a fire. Sometimes these become intermitant. You can just short it out or get another one at Radio Shack. Don't you hate these. With intermitants I end up running some wires back to a lamp hanging from the dash. Then drive around till it happens. I like things that just burn up.

 

[CHH777]

Where is the resistor assembly?

 

[Howard]

The resistor is under the hood next to the fan motor (sort of grey block with plug).

 

[CHH777]

Hey Howard,

You mentioned that this resistor is bypassed for full power? If so this may not be my problem as the fan either works at all speeds or not at all...

 

[Howard]

In your case I would suspect the brushes in the fan motor itself. Fairly easy to remove and strip (new brushes may be hard to find but a clean up may sort it out) only three screws and a plug.

 

[Crankcase]

BTW, the new blower resistor part is a redish color, so if the parts department gives you something else, you will know it isn't the right part.....

The bottom bolt is a PITA to take out too

 

[X-1]

Past experience has been blower motor, about 25.00's at the parts house.

 

[tenikiwon]

I think it could be a possible bad ground. I think I had my blower go out and it turned out to be a bad ground. I giggled the wires and all was restored.

In your case I do think it's the resistor.

 

[CHH777]

Thanks for the responses. I'll check the resistor and fan motor brushes...

 

[nhut]

I also have a problem with my fan blower. It seems to have a mind of its own and comes on when it feels like it. When it is on, it operates at any speed setting. I just changed the fan blower motor and the resistor.It is still doing the same thing. Any other suggestions would be greatly appreciated since summer in TX is around the corner.

 

[tenikiwon]

I guess I would look at the switch next. Also make sure all the connections are tight. Ground and Pos

 

[CHH777]

I replaced the blower motor; problem persists. Can someone post a pic of the resistor?

 

[FIRE and ICE]

I had a similiar prob with all or nothing blower motor operation. after much searching I found that the wires were shorting out where they entered the fan motor housing. ( they were flexing) my blower would cut out when I hit a bump and turn on after hitting another bump!

I replaced the fan motor with one that had a moulded connector and it worked fine after that.

by the way I had a smoldering FIRE in the resistor housing when some built up leaves came into contact with the HOT resistor wires!!!!!!!!!!!!

check and remove any debris in the housing around the resistors when they are out.

 

[CHH777]

Finally found the problem!

Turned out to be the relay in the fuse panel under the hood. Swapped it with the ABS relay and now it works fine.