91 F150 351.

My heater blower only works on high. Vent, floor or defroster all the same.

So the question is what controls the blower and what are some trouble shooting ideas? Or has anyone had this issue before?

 

blower motor resistor is out... $10-$15 and 15mins to change..

MOTORCRAFT Part # YH1698
DORMAN Part # 973011

 

Awesome, Wheres it located?

Thanks for the information!

Greg

 

It's right next to the blower motor-it has a wire harness that plugs into it.

 

PS if you get the cheap one at the part store spray the coils with some clear aerosol sealant.... That will keep the rust and water off the coils for a few extra years. You don't need to do it heavy... just a light dusting to keep moisture off them.

 

Nstueve,

Thanks for the info. Swapped it out today and all is good!

 

i have the same problem... where exactly is the blower motor located?

 

The blower motor is under the hood. It is next to the heater hose on the right side of the engine compartment and like said above the blower motor resistor is right next to the blower motor.

 

The new resistor only lasted about a month. (Never got around to posting) So I am going to buy a new one now and what type of spray do I use on it to make it last longer?

 

Spray?

 

Spray??? If a new resistor unit only lasted a month I'll bet your motor is getting old and the bearings are dry causing the motor to pull too many amps...

You can try to oil the bearings if you want but it won't last long....

 

yes guys, SPRAY! LOL...

The only reason I spray mine with a light layer of clear coat (or wild dog 40 depending on what i have at hand). It helps keep the salty wet conditions off the coils that go inside the heater housing. I have had a couple fail within 3-4 years on me, so I coat the coils to prevent the coils from rusting so quick (it could be b/c I am buying the cheapest resistors too ).

That being said the clear coating only helps to keep the resistor coils from rusting... You shouldn't be having a resistor fail within a month! How do you know it's the resistor failing???

 

How do I know its failing... When the fan only works on high, I replace that part and it works at all sopeeds. Lol. The truck hasnt been used much since the part was replaced. But I did notice some noise from the fan motor the last time I drove it. i will have to take a look.

 

I am having the same issue yet a new resistor did not solve. I am curious what else could be causing this issue, and how I would test the resistor. without being to intrusive I traced wires and saw nothing strange or unplugged. If someone in this trucks past bypassed the resistor where would be a likely location they may have done it? The motor still blows on high with the resistor unplugged, blows hard with no strange sounds (new to me truck so cant be positive on that),no noise or ozone smell when motor wont run on low. Could a faulty switch on the dash present this fairly unique symptom? I have no idea how long this has been going on. 91 F150 custom 302. I am no mechanic but I'm not used to running into something I cannot figure out even if the fix is over my head