Ideas, please - 208ZX blower motor cycles on and off - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 12 (permalink) Old 05-16-2018, 10:08 PM Thread Starter
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Ideas, please - 208ZX blower motor cycles on and off

I have my 83 280ZX Turbo back in service after a few years of work, but one problem persists.

When I turn on the heat/AC blower (manual control), it runs for 5 minutes or so, then the blower turns off. If I'm using AC, the compressor remains on.

After 3-4 minutes, the blower will turn on again, and the cycle repeats - a few minutes on, then it dies. A few minutes off, and I can turn it back on.

I've checked the fuse on the motor's lower area, and all wiring connections. I believe what's happening is that some component is heating up, then failing. When it cools off a bit, it will turn back on.

I can use help with how to test components or where to look for a bad part. Perhaps a relay?? If so, which one?
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post #2 of 12 (permalink) Old 05-17-2018, 12:51 AM
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Originally Posted by pilgrim View Post
I have my 83 280ZX Turbo back in service after a few years of work, but one problem persists.

When I turn on the heat/AC blower (manual control), it runs for 5 minutes or so, then the blower turns off. If I'm using AC, the compressor remains on.

After 3-4 minutes, the blower will turn on again, and the cycle repeats - a few minutes on, then it dies. A few minutes off, and I can turn it back on.

I've checked the fuse on the motor's lower area, and all wiring connections. I believe what's happening is that some component is heating up, then failing. When it cools off a bit, it will turn back on.

I can use help with how to test components or where to look for a bad part. Perhaps a relay?? If so, which one?
Did you try cleaning the fuse terminals?

1978 280z - stock L28 engine - Dallas, TX
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post #3 of 12 (permalink) Old 05-17-2018, 12:29 PM Thread Starter
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Originally Posted by chaseincats View Post
Did you try cleaning the fuse terminals?
Yup, I've had the fuse in and out a few times checking it. The intermittent nature of the shut-down is a poser to me. I have a spare amplifier and have swapped it (been a while) and there was no difference.
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post #4 of 12 (permalink) Old 06-19-2018, 09:38 AM
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Do you have Auto Climate Control in your car?

1983 NA
1980 Needs front clip
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post #5 of 12 (permalink) Old 06-20-2018, 06:35 PM Thread Starter
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Nope. Manual controls.
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post #6 of 12 (permalink) Old 06-21-2018, 03:59 PM
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I don't know anything about the ZX specifically, but in general:

That sounds a lot like a circuit breaker or thermal safety switch. Is there anything like that in the system?

Does it do it on all fan speeds? If just low/med, I'd suspect the resistor pack is faulty (assuming it has something like that).

Maybe it's just the brushes/commutator. How hard is it to pull the blower, take it apart, clean the brushes/comm?

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post #7 of 12 (permalink) Old 07-02-2018, 11:57 AM Thread Starter
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Originally Posted by kyle242gt View Post
I don't know anything about the ZX specifically, but in general:

That sounds a lot like a circuit breaker or thermal safety switch. Is there anything like that in the system?

Does it do it on all fan speeds? If just low/med, I'd suspect the resistor pack is faulty (assuming it has something like that).

Maybe it's just the brushes/commutator. How hard is it to pull the blower, take it apart, clean the brushes/comm?
Sorry to let this sit before responding - been traveling internationally and not great Internet connectivity.

It happens at all fan speeds. It definitely appears to be a component heating up and failing - but not sure which component. If you know where the "resistor pack" is, please let me know and I'll try a parts swap.
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post #8 of 12 (permalink) Old 07-20-2018, 01:40 PM Thread Starter
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There's some new info - last weekend I cleaned the blower power connector with Deoxit, and tried going on a long drive with the blower set to slightly below 1/2 speed. The idea was that if a component was heating and failing, perhaps a lower load on the blower would cause less heat.

It seems to have worked. The blower ran fine for half hour,but when I turned it up to nearly full speed, it shut down within a couple of minutes. I turned the blower off for five minutes, then back on at less than half speed. It ran OK for the 10 minutes it took to get home.

My deduction is that I do have a component heating up and failing, but not sure which one. Suggestions are welcomed - I can pick up most relays and parts on Ebay.
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post #9 of 12 (permalink) Old 07-21-2018, 12:27 AM
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Mr.Pilgrim:

Your accounts leave me wondering about your fan speed control; is it a stepped speed switch (3speeds?) or a rheostat?

A stepped fan control should have a couple resistor paths to create the slower speeds. This might be a place to look for continuity loss owing to heat warp/loss of contact.

The windings of a rheostat offer opportunities of heat-stress issues (broken winding, excessive resistance, etc.).

Unless you find a source of feed power interruption to the fan unit, it's hard to see how you can solve this issue without removing the switch and fan for bench testing.

Just a thought.



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post #10 of 12 (permalink) Old 07-23-2018, 05:53 PM Thread Starter
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The rheostat on the blower is continuously variable, not stepped. I've replaced it once, but having owned the car for 20+ years it's hard to remember when - certainly more than 10 years ago, as the car was in storage for 4 years. Mileage-wise, I am pretty sure it doesn't have 10K miles on it since I replaced the rheostat. I could probably measure resistance, but not sure that I can do that meaningfully without running power through it before testing - and it's not easy to get at.

I also have a spare blower motor and amplifier (one accumulates spares over years.)

I can't discount the rheostat as the cause, but perhaps it's more likely that another component is failing - but which one if what's puzzling me. I'm probably at a point where I need to do some part swapping, one item at a time. Ebay isn't a bad source for the components.

I'm still open for ideas on which parts are most likely failure points.
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