Heater blower gone mad

[Themoog]

A year ago I replaced the heater blower fan in my X5. In the last few weeks it's been going mad - runs OK for the first 10 minus then it speeds up and slows down constantly.
Has the FSR gone crazy? I'm sure I swapped it at the same time as the fan but I found 2 in the garage that are brand new and not OEM so maybe I didn't. What dya reckon?

[andrewwynn]

I would swap in different FSU. With experience it's a five minute job

[workingonit]

Originally Posted by Themoog

A year ago I replaced the heater blower fan in my X5. In the last few weeks it's been going mad - runs OK for the first 10 minus then it speeds up and slows down constantly.
Has the FSR gone crazy? I'm sure I swapped it at the same time as the fan but I found 2 in the garage that are brand new and not OEM so maybe I didn't. What dya reckon?

Apples to oranges, but the same anyhow.

I've got a '98 GMC Sierra pickup that has a similar problem, for several (maybe even 8-10 years, I forget). The blower will run fine for awhile, slow down , speed up, then quit. I turn off the blower for a minute or two, and sometimes it'll work fine, or I have to hunt for the speed it likes: low, medium, medium-high, and full speed. Or it won't choose to blow at all, and I have to repeat the process.

Blower: I've tested and replaced one blower that was going bad, and replaced its' replacement with another, though I didn't think it was drawing too many amps, and finally stopped replacing them. Fan speed problem stayed the same.

Control Unit: Same procedure. Replaced the original with a Dorman piece, then with another A/C Delco unit, and the fan speed problem persists.

Resistor (hedgehog): You guessed it, changing it makes no difference. I've used many (and have a new spare in the glovebox), practically one per every two years, and the fan speed problem always crops up.

Possible reason: After years of research, I've decided that GM used too thin of a gauge of wire(s) in the harness to the resistor and blower, and that it gets really hot after a few minutes, and the fan speed "merry-go-round" starts again. The previousowner ALWAYS ran the fan on high (I know, I rode with him for 7 years before I bought it from him), because the vent arrangement isn't the best. So, I too, usually started with the blower on high, just to initiate cooling faster. But sometimes, even if I used low or medium, the problem would start as well.

Possible (temporary) solution: A few times, after I thought I knew what the problem was, I would start out on each fan speed and run it until the problem started. Eventually, I found that "medium-high" was the sweet spot, and the problem did not happen. I now leave the fan on med-hi, and made sure that my wife does the same (it's her back-up vehicle), and the fan has worked OK for months now.

Possible (permanent) solution: There's an upgraded wiring harness on the market, with better connectors and thicker wires, that I'll buy the next time the fan speed problem happens, I swear. I haven't replaced the harness yet, because it's really buried under the dash, I'm old and don't work well under dashes anymore, and my penchant for work-arounds tells me to wire the blower directly to power...but my wife says no. Oh well, I'll get around to the proper fix some day.

[getty150]

My problem not as drastic as your but ...https://r.tapatalk.com/shareLink/top...ink_source=app

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[andrewwynn]

Contact problem: deoxit gold


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[getty150]

Originally Posted by andrewwynn

Contact problem: deoxit gold


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Yeah, I've got it!
Use on the fan connector right?

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[andrewwynn]

FSU plug yep. Just unplug replug a few times usually scrapes off enough contact gremlins to make it work for a while but deoxit will actually fix it if contact resistance is the problem


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[getty150]

Originally Posted by andrewwynn

FSU plug yep. Just unplug replug a few times usually scrapes off enough contact gremlins to make it work for a while but deoxit will actually fix it if contact resistance is the problem


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Good reasonable sound suggestion thanks

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[Homerlovesbeer]

Hopefully that does the trick

[andrewwynn]

I had one FSU overheat and i left it dangling in the foot well it stopped overheating. That's another failure mode to be aware of