Hello, everyone. I've searched through all the forums for a similar problem and can't seem to find this variation of the blower motor demons...2002 Maxima GLE - auto climate control. Blower comes on/off intermittently without warning. I've taken out the glove box to locate the culprit (I thought bad wiring or loose connection) but all connections are good. Fan amplifier seems likely BUT everything I've read states that when that fails you get either high setting only or nothing. Not the case with mine. All 4 fan speeds work when on. I wired the blower directly to a power switch to test if it fails, and it has not failed through constant power. I saw the repair tutorial for the fan amplifier so I'm trying that, but the question still remains. Can the system act as mine does if the fan amplifier fails, or am I chasing a ghost here? I don't want to throw hundreds of dollars at parts that aren't necessary. I know the connections are good, and the blower itself is good. Any ideas?

 

Did you check anything in the control panel? There are rare cases of problems with loose connections in the under hood fuse box where the blower motor fuses are. And there have been intermittent fuses.

What you need to do is hook up a voltmeter to the wires on the fan control amplifier when the motor doesn't run. This will tell you if the control panel is telling the fan motor to run. I can get you the voltages that should be present, but I'm not at home right now.

 

I pulled out the fan control amplifier and the circuits were a bit dirty, I'm not sure how gunk gets into there since it's sealed. Anyway, I cleaned that up a little and used the tutorial I found to solder a jumper to the 2 outside leads...apparently that bypasses the thermal circuit that could be dead? However if it's dead then it should either be full blast or not work at all. Anyway - so far it's working, but again my problem has been intermittent so I'm going to give it a few days before I call it solved and buy a replacement; I assume it's not ok to operate with the jumper permanently. Or is it? I'd happily sink that extra $70 into the power steering pump that just failed.

Thanks for the reply, Dennis - if this isn't the solution then I will be testing the control panel and connections like you suggested!

 

That thermal circuit thing you referred to is in actuality a fuse. So jumpering/bypassing it won't have any effect on the different speeds, they will be the same as they were. Since the fan ran sometimes, I hate to be a pessimist, but I doubt if you fixed it.

As you probably saw, there is a big transistor in the fan control amplifier. The control panel fan speed setting turns the transistor on a little , medium or all the way. If the transistor fails, the fan will either not run at all or only run full blast, no in between. Not at all is by far the most common.

As far as using a jumper to power the fan, this won't hurt anything as long as you have a fuse in that jumper wire arrangement. But then, that is just for safety reasons if the fan motor were to develop a short. If you have a good fan motor that you can guarantee will never go bad, you don't need a fuse.

 

That's great information, thanks! I didn't take a picture of the jumper I ran (I honestly didn't think it would work) but it was the thermal circuit. I didn't realize it was a fuse. The blower motor seems pretty strong - however I would rather err on the side of caution and replace the fan control amplifier if the problem doesn't reappear. When it would shut down before, it was intermittent to the tune of two or three times per hour of driving. It's been several days without fail so far but I haven't made any super long trips. It's one of those things where I'm afraid to do anything differently to jinx it because it's 8 degrees here!