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328is in need.
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6 Posts
Discussion Starter · #1 ·
I have a 1997 328is with some odd heater/AC fan behavior going on, and would like some suggestions on what components to troubleshoot & replace and in what order so I don't waste time & money. I did search the forum first, but am not finding the same issue.

So, about 99% of the time the cabin fan for heat/AC will not work. Sometimes on hot days when the car's been parked in the sun, out of the blue the fan will suddenly start working when starting the car. But, that's very rare. I have the 328 model with the digital display control, and it appears to be responding normally, but the fan doesn't kick on. With the rainy season coming, I need to fix this asap.

I have a Bentley Publishers BMW Service Manual, which details the parts of the system. I've worked on american and japanese cars since I was a kid, so I feel confident in my mechanical abilities. The manual indicates a lot of components that could be at fault here, including the blower motor, the motor's resistor pack, heater valve, heater core temp sensor, control head, interior temp sensor fan, etc.

Any help you could provide in resolving this issue will be greatly appreciated!

Thank you,
Kevin
 

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BE IRIE
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885 Posts
So the fan does not go on when you put it on low medium or high?

Seems like a circuit issue or just electrical connection. Have you tried to remove the covers off to reach the blower from the engine bay and clean the terminals?
 

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328is in need.
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6 Posts
Discussion Starter · #3 ·
that's correct, it doesn't work in any position - it has the digital control panel, so it doesn't work at any level in the variable band: lowest, middle, or highest. i haven't tried cleaning the terminals, but i'll give it a try today! in the rare case when it suddenly works, i think that it only works at the highest point, and if i lower the speed, it will peeder out in a couple minutes, but when i return it to the highest position it won't begin working again. tricky bimmer. i read this thread that seems to point to the resistor, but i'm not experiencing the same symptoms and can't replicate the issue as he can: http://www.bimmerfest.com/forums/showthread.php?t=488926
 

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BMWCCA HPDE Instructor
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23,469 Posts
If the display on the HVAC control unit lights up and responds to button pushing, there is a 99% chance it is one of the two following things:

1) Final stage unit
2) Blower motor

I tend to lean toward option number one. It's a very common problem in E36s, and is easy to fix. Symptoms are intermittent blower functionality, which eventually leads to the fan not working at all. I had this exact problem in my car a few months ago.

Since your fan does come on in rare instances, it's most likely not a bad blower motor.

If you want more reading, search for "E36 final stage unit".
 
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