Truck fan blower doesn’t work on high speed

Maintenance/Repairs
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1

2011 Ford f 150

For a couple of years I’ve had an issue with the high speed fan setting on my truck. After a while, all speed settings started to fail. The blower motor would make this weird moaning sound and no air would come from the vents. After looking at different problems online, I decided the fix would be to replace my blower motor resistor. Once replaced, my problem was solved until a few weeks later, I had the same problem again.
Today I removed the blower motor and ,while pulled out of its cavity, the motor worked perfectly on all speeds. Once secured back into its cavity, the moaning/no air flow would start again. Does this indicate a blockage somewhere in my vents/air intake?

2

The motor might spin freely, but the cage part (w/the fan blades) could be sticking & stalling the motor. Are you able to verify the fan blades turn freely? If not, there could be leaves/sticks obstructing something inside the fan blade cavity.

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3

Hi there, thank you and sorry for the late response, I never got a notification.

I was able to see the cage/blades spin freely on all speeds, as the motor and blades are all part of one assembly. I even turned the fan speed all the way up (blades spun fast with no problem) and then inserted the motor back into the hole and it would immediately bog down once fully seated. Once it was pulled out, the blades would spin freely again. Another problem may be that something is physically restricting/blocking the blades from moving once inserted. Then again, it spins fine on all other speeds which is what makes me think it’s blockage in the vents.

4

maybe the motor is weak. it spins freely when out and there is no pressure on it. but when put back together its staining. just a thought.

5

A lack of airflow from a blockage will cause the fan to spin faster. Something else is going on. Is the squirrel cage rubbing against anything in the heater box, like an errant piece of foam rubber seal?

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6

Definitely could be a possibility. I’d have to price some motors out. Thanks for the response

7

I’d never thought of that! There could be something rubbing against it, I’ll have to have a look.

8

I ended up buying a new motor from 1A auto, slapped it in there and all speeds work again! Hopefully it lasts, thank you all for your help.

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9

it’s also a good idea to look at the wiring going into the resistor for the blower motor. these can get hot and melt and then start to lose connection. It may work now, but wiggle it and it may not.

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10

If you are able to feel the new motor casing without too much effort, check it occasionally after running, making sure it isn’t getting overly-hot. If it is there may still be a problem, for example with the air flow path. An electric motor that overheats will eventually melt the insulation, developing short circuits in the windings (coils). The electric current not following the intended path reduces the magnetic field strength and reduces the motor’s power.

12

I didn’t notice any signs of melted/compromised insulation on my old motor. There was, however, quite a bit of carbon dust from the brushes.

13

It can be hard to tell just by looking. The wires that form the coils don’t have the standard plastic insulation material, instead they are coated with a very thin layer of insulating paint. Not to say melted insulation was the cause your old motor’s demise, could well have been a problem with the brushes or commutator. The latter usually don’t cause overheating, just under-power.

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