Reader Is on the Right Track

Dear Car Talk:

I’ve had the blower motor replaced on my 2013 Nissan Altima. Then a fuse blew. A new fuse was put in. The new fuse blew. I took the car to a place to check the electrical system. They said the electrical system was fine. They replaced two fuses and said it shouldn’t happen again.

My blower motor, when driving, goes from high to low without me adjusting anything. I think it needs a new resistor, but the shop says the fuses should take care of it. They say just wait to see if it blows again. But that means another trip to the mechanic.

I don’t know what or who to believe. I just need to know if I’m on the right track or not. Should I go someplace else? — Donna

I think so, Donna. Fuses don’t just “blow” for no reason. And whatever is causing it will eventually cause the fuse to blow again.

Was the poltergeist fan speed the reason you had the blower motor replaced in the first place? If so, I’m afraid they may have sold you a blower motor you didn’t need. But let’s assume the fan speed gremlins arrived after the new blower motor.

Normally a fuse blows when an electrical device is drawing too much current. The whole purpose of the fuse is to sacrifice itself and cut off the power to that device before the device can draw so much current that it overheats and starts a fire. Although maybe a fire sounds like a good solution to you at the moment?

So the fuse is doing exactly what it’s supposed to do. The question is, why? Normally, it means that something is forcing the blower motor to work too hard. What could that be?

Well, it could be that they sold you a rebuilt blower motor, and it’s simply no good. It could be that the guys who installed the blower motor accidentally dropped something into the housing, like burrito supremo. Or maybe some twigs or debris got into the fan housing and are making the blower motor work extra hard to turn the fan.

Another possibility is that the blower motor relay could be bad. And finally — and most likely — it could be exactly what you suggest, Donna; a bad resistor.

The resistor is the part responsible for changing the speeds of the fan. So if your fan is pulling a Friday the Thirteenth, the resistor would be the first thing I’d suspect. If you came into the shop, I’d probably get you a new resistor for $35 and a blower motor relay for $25. After all, I want to make sure you don’t come back!

To install the resistor, I’d need to remove the glove box, so there’s a good hour or more of labor involved. And while I had the glove box out, I’d pull down the blower motor housing to make sure your fan is turning easily and freely and that there’s no debris in there getting in its way.

So I’d take it to someone you have more confidence in, and be sure to tell them about the issue with the fan speed. That’s a flashing red light that says “RESISTOR.” Good luck, Donna.

Todays Car-o-Scope

What the stars say about your car for 10/25/2020
You will discover the cause of that nagging feeling that you've forgotten something important, and it will cost you $1200.
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