HVAC fan

[GTRS Fiero]

My HVAC fan runs faster at the lowest setting than at the first dot.  My first thought would be the resistor, but that makes no sense.

To pull the fan, how does the squirrel cage come off?

[Fierofool]

Your theory is correct.  There are three resistors on the ballast unit but there are four speeds for the fan.  The larger resister is the low-speed circuit.  The high-speed ciruit doesn't have a resistor.  If the larger coil has burned in two, it should allow the fan to run at full power. 

To remove the squirrel cage from the motor, remove the nut in the middle.  The shaft should be flat on one side to keep the blower from spinning on the motor shaft. 

[GTRS Fiero]

If the large resistor lost some coils, yes, but if separated, I would think that the fan would not turn at all.

For the squirrel cage, I want to remove it without taking the entire dash out.

[Fierofool]

It comes out through the front as part of the motor assembly.  Easily removed.

[GTRS Fiero]

Well, I found some interesting things.  First, I removed the squirrel cage, and found this:


The insulation was actually inside the squirrel cage, and obviously made the motor loud, because the cage was off balance.

After re-assembly, the motor now runs quietly.

[GTRS Fiero]

Next, I removed the heater resistor.  This one was actually more scary.  There was a piece of thread all intertwined in one of the coils, but also more insulation.

[GTRS Fiero]

The resistor itself was not only shorting one coil against another, but had a broken coil, just as Fierofool suggested.



If you look closely, you can see the burn mark on the broken coil at the bottom against the wire going up to the coil on the right.  Looking at the coil on the right, you can see the thread at the very right middle of that coil.

[GTRS Fiero]

Forgot to mention that the fan speeds now work properly, after replacing the heater resistor coils.