Blower fan shuts down after a few minutes

[Pilgrim]

The car: 1983 280ZX Turbo. When I run the vent/AC blower fan for a few minutes, the fan dies. This happens whether or not the AC is on. If the AC is on, the compressor is still engaged but the fan blowing the air inside just dies. No fuses blow, but the car has to sit for an hour or more before the blower will work again.

Since no fuses are blowing, this has the appearance of a component that's heating up and failing, then working after it cools off. But which component? Or is my reasoning faulty?

Ideas...?

[5thhorsemann]

That car is unknown to me, but on some cars there is a resistor bank in the duct used to controll the fan speed. Check your FSM wiring digram to locate the speed controler and focous on the comon terminal wire. Hope this helps.

[Pilgrim]

It's not the amplifier - that was the first candidate. Now checking the blower relay that mounts next to the amplifier. The FSM says it's most likely culprit.

[palladin]

It is the auto air function. By design the blower slows down as you approach the designated temp but the lo-hi function was supposed to override that. At 28 yrs old the elec contacts have gotten dirty. There are close to 10 sensors whose measurement of resistance determines blower speed. Down load the FSM and AC supplement from xenons130.com.

[Pilgrim]

I have manual air, not auto air.

[Pilgrim]

Thought I had traced it to the blower relay that mounts on the underside of the blower housing. By replacing it, I determined that it's unfortunately not the problem. Will go through the FSM check procedure this weekend - I have the dash vent pulled to get at the connector behind it - and see what I learn.

[Pilgrim]

Latest indication is that it's the rotary fan speed switch on the AC/Climate control panel. Rats. Well, I had to pull the dash to replace all the vacuum lines anyway.

[Pilgrim]

Just for your info - the car is down for now...I pulled the dash and replaced the harness with the rotary fan switch and the micro-switch that toggles the AC on and off. I'm replacing the vacuum lines as well, and having trouble finding vacuum hose that's the right outside diameter. It has to fit into some vacuum connections where exterior size is an issue.

[Pilgrim]

So, after two months of sitting while I got around to the vacuum hoses, I have replaced the fan speed rheostat and AC engagement switch that are inside the climate control panel. They come as a unit on a small harness.

Fired it up, drove it, and no fan. Nothing. No AC engagement either, which is increasingly odd because when this started, the AC compressor would engage even when the fan wasn't running.

Guess I'll go back through the electrical diagram to see if I can figure out where the signal is getting dropped. Before installing the dash, I checked the little AC engagement switch (a small push-button contacted by the AC lever; it mounts on the back end of the climate control mechanism) and it definitely is good. At least the AC compressor ought to be engaging.

I'm stumped for the moment, but when I find the problem it will most likely be something very basic and simple.

[Pilgrim]

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 wiring, 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 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!!

[Darrel]

That is the fuse for the a/c according to the factory service manual.

[Pilgrim]

That is the fuse for the a/c according to the factory service manual.

That makes sense...and confirms which circuit is involved. Not that I didn't already pretty well know that.