Blower fan shuts off after a few minutes - Why?
 

I'm having a problem with my 1983 280ZX Turbo. The blower works fine on vent and heat, but after just a few minutes (sometimes only 2 or 3) with the AC on, the blower fan stops working.

The AC still runs, but the fan needed to delivery the cooled air stops. Turning the AC off doesn't bring the fan back to life; it will only start working again after the car has sat for a few hours.

This has happened 4 or 5 times. No fuses have ever blown, including the stealth glass tube fuse that's mounted under the blower motor. After sitting for a few hours, the fan works again. But hop into the car when it's hot and crank up the AC - and the fan runs for a couple of a minutes, then shuts off.

If the car sits for an afternoon or overnight, the fan works again.

The way this reasons out to me, it seems like running the AC must make some component associated with the blower fan heat up and fail. When it cools off, the fan runs again. Running the fan with no AC doesn't cause this problem.

Does this sound likely to you? If so, what component do you suggest I check? I was thinking of the amplifier mounted under the blower, but it is used all the time - both with and without AC.

do you have the auto climate control or the manual one??? if its the auto one its most likely the temp sensor doesnt work. the auto system sucks even on the best of days. the sensor isnt used for vent or defrost so that prolly why those work. if you have the manual style then you have to trace relays and find out if one is overheating. mine was the one under the heater motor. it looked fine outside but was melted inside.

I have the manual AC system. Another party suggested checking the temp sensor - but I don't think the manual system has one.

Relays sound like a good idea...I'll check those and see what I can find.

I thought it was the blower relay, mounted on the underside of the blower housing. Replaced it - no luck. Will go through the FSM check procedure this weekend - I have the center dash vent pulled to access the connector.

Bad blower fan!or bad amplifire(goes in the blower motor housing)
Happened to me last summer,just replaced it with another used one....works fine after that.

I have another amplifier - swapped that out and still have the problem. I have two spare blower fans but the one in there has only been in it 2-3 years. This one is tricky....

OK...more about this problem.

I traced everything, then finally pulled the dash and replaced the wiring harness which connects the blower rheostat and AC controls to the chassis wiring...it's accessed by a connector behind the center dash vent. While I was in there I replaced most of the vacuum hoses under the dash, except for a couple that wind around behind the heater unit.

The wiring harness in question connect to the blower rheostat and also has a push-on switch that mounts inside the AC control unit. When you move the top lever into any of the three AC positions, a projection on the back of that lever pushes the tiny ON switch on this harness to engage the compressor.

I put it back together - and still no blower, no AC. DAMN! I've spent the last couple months alternately glaring at it and flipping pages in the factory service manual.

BUT!.......................!

There's good news...not necessarily a permanent fix, but at least a temporary positive note.

Last week I dug into the ZX and checked the wiring again using the FSM directions to check the wiring harness for the AC unit (for at least the 6th time), and darned if I didn't find a blown fuse. It was the 20A fuse on the bottom right corner of the fusebox; I didn't check the label on the slot, but I replaced the fuse and my blower fan and AC compressor both work!! I believe this is the AC fuse.

I drove it around town and on the highway for more than 1/2 hour and everything continued to work.

Do I think the problem is solved? Not really. I think I fixed a symptom, but there's a reason the fuse blew - and that reason is the real cause. However, I'll live with this for the time being. I suspect the test will come when the weather warms up, as the original problem occurred when days were hot. It's possible that when I replaced the wiring harness for the blower fan and AC control unit that I blew the fuse - and if so, I'll be a happy guy.

But after six months of down time, pulling the dash and replacing wiring and vacuum hoses, I'm damn glad to have it driveable again!!

did you actually check for power and ground AT the blower motor when the symptoms occur? also when it stops working, give the blower motor a good kick, if it comes back to life, it needs a blower motor.

It's hard to remember what I've checked over the past months. ...but I know I confirmed power and switched both fan and amplifier. Ground has to be good or they would not operate.

I suspect that something in the circuit is drawing too much power and blowing the fuse, and logic tells me the pattern points to the AC system. As weather heats up I will probably learn more.

I am having exactly the problem as described. Yes, only on hot days when I need the AC most. Did the fuse replacement permanently fixed the problem? I always thought a blown fuse will cut off the 12V permanently and that the blower should not work even on a cool day. I replaced a head unit with climate control recently and that could be the cause of this problem..

I haven't solved it. I have noticed that if I run the fan at half-speed or less, it runs for a longer period but will eventually shut off. I am confident that there is a component overheating as the fan runs, but I haven't been able to find it yet. The car runs great, I just can't use the blower for more than about 5 minutes at a time. Given time, it will evidently cool off, and then it will run again for a few minutes. I'll try to remember to post when I find a solution.