2005 Chevy Impala blower motor issue?

Maintenance/Repairs
1

A couple months ago, I turned my car on, and the blower motor, which is usually on at SOME speed, was giving me nothing. Fiddled with the knob for a couple seconds, and nothing. Drove about 500m, and noticed smoke coming from the vents. Drove back home immediately and parked.

Since then, the car has been drivable, I’ve just left the adjustment knob in the OFF position. Yep, no AC this summer. Awesome. Anyway, with cooler temperatures approaching, I will definitely need some defog/defrost action if I plan to continue driving.

Fast forward to yesterday. Bought a new blower motor. Ripped out the old, shoved in the new. Nothing. OF COURSE… when the old motor shorted (?), it would have blown the fuse! Sure enough, 30 A fuse in the box under the hood. Scorched. Back to the store for a new fuse! New fuse in place, let’s try to hook that new blower motor up again… HOLY CROW. As soon as I connected it, it turned on full blast! In my hand! The key wasn’t even in the ignition! Scared me half to death.

As a non-car guy, I only know what I have already Googled. I understand that there is a motor and a resistor module, and a fuse and at least four relays in the box under the hood labeled “fan control.” At least one of these has failed or is failing.

Do fuses smoke when they burn out? Or would the smoke have been from a short? Is the motor fried? Did the resistor go bad?

Everything as is, the old motor is always off and the new motor is always on. So this would lead me to believe that the old motor burned out, yes? But WHY does the new one not work propertly? Is the resistor bad, too? I’ve read that a bad resistor can lead to a fun being stuck on a certain speed (ie. high). Would that apply even when the car is off? Or is it more likely that one of the relays is stuck in the on position? But if THAT were true, why can’t I adjust the speed?

I am so confused and lost!! Any tips??

Thanks for reading,
Jared

2

Chevy’s are horrible about burning up blower motor resistors and the wiring going to them. Find it and check it out. It would not surprise me at all if you found melted and scorched wires and plastic. Although, I’m not sure there is a wire there that is battery power- I would expect only ignition power. So you may have a relay burned up too.

in my wife’s ‘12 malibu, the resistor is up where the floor meets the under dash- right where my 6’ son likes to put his feet… (not sure if your '05 Impala is located in the same place.)

3

A fuse will seldom smoke when it blows. You may hear a faint “tick” sound sometimes when a fuse pops.

These failures often happen in a chain. Worn blower motor draws more current which can in turn burn up the resistor pack or blower module, fan speed switches, and fuses. Odds are the resistor pack is failing/failed and it could also be that the wire connector at the resistor pack has burned from long time high current draw of the blower motor.

I suspect the smoke, if not from the blower motor, came from either the resistor and/or the wire connector at the resistor. My assumption is that if the connector at the blower motor is burned you would have noticed it.
It’s possible a set of contact points in one of the blower relays could be stuck and causing the fan to run even in the OFF position. Tap the relays firmly with a screwdriver handle and see if the fan stops.

4

Thanks for the tips! I haven’t removed the resistor yet… but I examined the wiring under the dash. The wires and connectors all appear to be just fine. Nothing looks burnt or melted. I will try tapping the relays and see what happens.

5

The blower function/speeds is controlled by the logic in the HVAC control module.

image

Tester

6

Okay. So. Connections look fine. Relays all removed. Blower motor still consta-on. I will try removing the module on the dash!

7

Will this simply need to be replaced? I pulled it out, but it’s pretty impenetrable. I cant tell if there’s anything wrong with it.

8

OH MY, I’M LOST. All the relays are unplugged. The HVAC module is disconnected. There is no obvious damage to the wires or resistor pack. But still… the fan is constantly on, even with the key out of the ignition. Whaaaat?!

9

Remove the 30 amp HVAC blower fuse from the fuse box under the hood.

If the blower stops running, the problem is with the blower motor control processor.

image

Tester

10

Okay. So. With the fuse out, it stops. I disconnected the wires from the resistor pack and checked the voltage across the red/grey wires as I turned the speed control knob. The voltage increases as the speed increases. I’m assuming this means the logic in the dash module is working.

So… the inputs to the resistor pack are good and the outputs are bad. I guess that diagnoses the problem, then?

The “resistors”… that must be the blower motor control pack, correct?

11

That 30 amp fuse to the blower motor control processor is hot all the time.

So if you pull the fuse and the blower stops, it’s gotta be the processor.

Tester

12

Thanks, everyone! Put in a new resistor, and all is well! Well. And new motor. And new fuse. LOL.

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