AC Blower Not...Blowing

I’ve got a 2003 Mazda 6i with the manual air conditioner (if it matters). About a month ago, the blower stopped blowing. The AC is still working (if I’m going fast with it on, cold air still comes out of the vents, though very slowly), but no matter what I have the control speed set to the blower doesn’t blow at all.

Well, sort of. A few times (maybe four out of several dozen car trips) it does come on, seemingly randomly, after I’m driving for a while (I mean a while - 30-60 minutes later). Once it comes on it seems to stay on. If I turn the car off and back on again, it’s still on. If I walk away for awhile (I assume, if I cool it down) it is dead again.

So…I’m sort of suspecting a bad ground wire somewhere, rather than a bad blower motor or a bad speed resistor (which I’ve replaced once already about a year ago). But I’ve pushed, pulled and wiggled on all the wires I can find under the dash that are related to the AC controls and the blower. No effect.
Anyone have any idea?

Also, if I can’t figure this out, who should I take this to? An AC guy? An electrical guy? The (shudder) dealer? I’m at a loss. For weight. I live in Texas and it’s (still) hot out.


I would suggest a local shop that works on electrical stuff on a regular basis.

A dealer likely would be able to do a good job, but it likely will be a lot more expensive. My second choice would be a general local mechanic.

You probably just need a new blower motor. Turn on the fan and whack the bottom of the blower with a rubber mallet or some other similar thing. If you can get any life out of it that way then just replace it.

If you have a multimeter - or even just a 12V test light - you can easily find out about the power delivery.

A variable resistor for the blower motor is the first likely suspect, if replacing it again fixes it, it was bad. A bad blower motor causing the resistor to fail is a possibility.

So…to test the power, I just unplug the blower motor and check the power across the wires? How about the resistor (which is such a pain to get to) any way to test that? (I always thought it’d work on 4 (i.e. no resistance) even if it was bad…)

The fan should still work on its highest speed if its just the resistor that went bad.

And yes - all you need to do is look for 12V at the blower connector. You should end up with 12V at each switch position (lo - hi, whatever they are numbered).

That’s what I thought (about the highest speed); unfortunately it’s not working on any setting so that’s why I was assuming it wasn’t the resistor. I’ll test the wires going to the blower to see if I’m getting 12V first. Thanks - I’ll let you know!

I’m in agreement about the blower motor being bad and possibly the resistor, all depending.

You might also check the fuses. Sometimes when a blower motor drags badly for a long time or just flat seizes up it may cause a current surge and pop the fuse. Fuse replacement will not be the cure for the problem. I’m just mentioning this in case you have a situation with no power present to operate the blower motor.

If you find that power is getting to the blower connection with reference to ground then there may be a thermo-protector inside the resistor pack that has gone bad. That would kill the blower action on all speeds. If you don’t see power at the blower connection and all the fuses are good then I suggest you check the blower relay and the connections to it for a problem. You can verify that the motor is ok by tieing power directly to it.

I think you are going to find that the brushes in the blower motor are worn out or junk has built up on the armature. either way, it is very difficult to get the blower motor apart so you just have to buy a new one.


Okay, I took the multimeter out to the car and here’s what I found:

  1. At the plug to the blower motor, I was getting no volts, no matter what setting the fan speed switch on the dash was set to. So I’m guessing it’s not the blower motor (at least, not only the blower motor, but let’s be optimistic).

  2. After killing myself I managed to unplug the four-wire plug going to the resistor. I tested it and found that I was getting 4.8v on one of each of the four wires depending on which setting the speed switch was set to.

So…assuming that 4.8v is the correct value (anyone know?) I’m pretty much guessing the resistor is the culprit? What do you think?


I’m not sure how you referenced your meter when you measured the voltage at the motor connector. If you measured across both terminals of the motor instead of using ground as the reference I could see how you got those reading.

Most blower circuits run power first from the fuse, then through a relay, to the motor, to the resistors and switch, and then to ground. The trouble is most likely with the relay. If your meter shows no voltage at the motor connection while the other meter probe is tied to ground then the relay needs to be checked. As for the correct voltage there will be 12 volts across the motor connections when the motor is running at full speed. Slower speeds will drop some of that voltage across the resistors.

Maybe I measured it wrong then. I unplugged the blower and took the two leads and connected them to the two wires that were previously plugged into the blower (thinking that one of them is ground). That’s where I got 0v. Is that wrong? Do I need to touch one wire and the other test lead goes to ground somewhere?

Found it! I pulled the relay and one of the pair that’re supposed to show continuity are showing an open circuit. Plus there is some crud on one of the posts and it was quite warm to the touch when I pulled it. Awesome!

Put in the new relay and AC is working like a charm. Thanks!

Thanks much for reporting back. Most often we never do hear about if or how issues were resolved.

I will mention though that you might still want to worry about that blower motor. If it is drawing too many amps it can burn up bits of the power system feeding it - like resistors and relays.