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Blower motor resistor - check before buying

I have a 2002 Nissan Maxima with 118K that the heating and a/c fan always blows on high. Even when you turn everything off. I’ve been told it’s the blower motor resistor. Part is $103, is there anyway to check with a volt meter before purchasing new one? Once I buy the new one I don’t think I can return

I haven’t seen every variation of these but quite a few. The ones I’ve seen use a small relay for high speed and series resistors for the lower speeds. If the relay got stuck ON, it could continuously run on high speed regardless of switch selection. The relay is located right on the resistor pack card on the type I have encountered. Pull the resistor pack out and use your meter, but measure resistance rather than voltage to see if the relay is bad. I actually repaired the one from my Trailblazer. It blew out a trace when squirrels decided to store nuts in the cage, That overloaded the motor and blew a trace on the resistor card. Had to remove some of the conformal coating to expose the traces and repair it but much cheaper than the $55 the part cost new. Been working fine for years ever since then.

Got any U-Pull it junk yards? Id go there first and just grab one from there. When y ou look at it you will see 3 little wire coils (old style) and if they all look cosher with no breaks in the wires then it will most likely work just fine. Many times you can get to the little bugger by dropping out the glove box, it is often directly behind the glovey. It’s held in by one screw (maybe a couple screws and will have a plug going into it) If you see something like this behind the glove box you just found your resistor. It is a rather small yet delicate part so be carful handling it and try NOT to touch or handle the wires, they dont like being fondled. The part will fit inside your tool box very well…

You might consider eBay.

To know for sure you need to access the resistor and do some testing. If the resistor is bad you really need to consider the strong possibility that the resistor failed because of an aged and dragging blower motor.

With an ammeter you could test the current draw with the blower motor on the HIGH position. If the motor is pulling a large amount of current (say 20 amps or more) then the motor is on the way out also.

It’s not the resistor(s).
It would have to fail in a short circuit, and resistors don’t do that (except high voltage carbon resistors).
Like Turbo says it could be a relay, or the controlling switch itself.

If it is the resister, buy it off the Internet at greatly reduced price - I found one for your car for under $30.00.

If it is a bad high speed relay the OP can take it out of the circuit by cutting one lead or trace and he’ll still have the lower speeds without buying a part.

Feeling Lucky ?

Hey, it’s probably the resistor. Then if the new resistor blows shortly after installation then it’s probably the blower motor (and another resistor).

You could pay some outfit 100 bucks to diagnose it and then mark up the price on parts to fix it or . . .

. . . roll the dice, be a “big shooter” and buy a resistor and stick it in there. If you’re lucky then the problem’s solved. If not, well then there you go.

This is the world of DIYers. Win a few, lose a few, but in the end you’ll usually come out way ahead and the ones you lose will make you smarter for next time.

Harry Callahan: “I know what you’re thinking. “Did he fire six shots or only five?” Well, to tell you the truth, in all this excitement I kind of lost track myself. But being as this is a .44 Magnum, the most powerful handgun in the world, and would blow your head clean off, you’ve got to ask yourself one question:
Do I feel lucky? Well, do ya, punk?”


Somebody explain to me how a resistor could make the blower run “Even when you turn everything off”!

That’s just blind parts changing.

Basic electricity isn’t that mysterious.

I agree and I’m wrong. While thinking about this I completely forgot the “everything off” part, which I assume means fan switch and/or ignition switch off.

Off the top of my head I don’t think these cars use a high speed only relay but I could be wrong on that.
Some late model cars use blower control modules so a faulty module is always a possibility.

Back to a check of the schematic and a review of the technique used is called for here.Once you know the technique you can either follow the flow chart (hopefully there is one) or come up with your own.