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Thread: I'm terrified of a blower motor fire..

  1. #1
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    I'm terrified of a blower motor fire..

    I was driving today and smelled a burning smell. Pulled over and didn't notice any smell under the hood or anything. As soon as I got in I noticed the smell again. I have a 6/1990 with no cabin air filter and no sword. What's the cause of the fire? The resistor? The motor? How do I prevent this? I can't seem to find consistent information. I've started keeping a fire extinguisher but it's winter and I can't go without the blower.

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  2. #2
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    Is your fan making a lot of noise? It will seize up and catch fire. Also you should change out the 30 amp fuse for the fan to a 20 amp.


    Andy

  3. #3
    moroza's Avatar
    moroza is offline MORΩN ΛABIA BMW CCA Member
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    Seems to be a few things that can cause fires:
    - Fan motor seizing, overheating, catching fire. Should blow the fuse but doesn't always, hence the recommendation to switch to a 20A fuse.
    - Wiring short-circuits because of insulation either cracking (moderate overheating over time, from moderate overloading) or melting (severe overheating at one time, from severe overloading). Same thing regarding the fuse.
    - Leaves get onto the resistor and catch fire.

    If the fan is noisy, by all means investigate it. But just because it sounds ok doesn't mean it's healthy. And vice-versa: my motor was healthy with ample brush material left, but the hamster-wheel fan impellers were deteriorated to the point of shifting side to side in a turn and hitting the housing.

  4. #4
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    I replaced the resistor and I saw no leaves. Does this rule that out?
    Last edited by shogun; 12-04-2018 at 12:37 AM. Reason: double posts merged
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  5. #5
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    How are you mounting the fire extinguisher? Loaded question
    - Brent
    www.angry-ass.com

    Quote Originally Posted by danespann View Post
    Every E34 needs the same things in the end.

  6. #6
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    Quote Originally Posted by Spaceturtle917 View Post
    I replaced the resistor and I saw no leaves. Does this rule that out?


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    I have seen the cabin filter burned by the resistor.. pulled it out and a nice square shaped black charred space in that corner.... check the filter?

  7. #7
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    Quote Originally Posted by jehu View Post
    I have seen the cabin filter burned by the resistor.. pulled it out and a nice square shaped black charred space in that corner.... check the filter?
    His car doesn't have a filter, early E34s didn't and I'm pretty sure all 535s didn't.

    Chances are that the blower motor could be running hot since it likely still has the 30A fuse installed and is burning some of the leaves and debris that's built up around the motor over the last 30 years. This was the leading cause of the fires so most people take the motor out, clean the area and then install a 20A fuse since the motor should at most only draw about 15A. I recently had this done myself since my motor started squealing and I knew there was a bunch of leaves back there, so I got the motor changed and all the leaves taken out. There were a lot of crispy dead leaves in there and combining them with a hot blower motor was a scary idea.

    So if you're afraid of the car going up, check that resistor (since you don't have the sword, yours will be on the drivers side and will have a blue tab) then replace that fuse with a 20A. Then for ultimate safety, take out the blower motor and clean that area out.

  8. #8
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    I have the exact same problem. I tried putting in a 20A fuse but, the blower wouldn't start. I checked the fuse and the fuse was blown. I put the 30A fuse back on and it started up again. I do get the light burning smell from time to time.I turn off the heat as soon as I smell it. I'll try another 20A fuse again but, I don't think the fuse will hold and I'm not sure why.

  9. #9
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    Blower motor and resistor pack combined should not be pulling 30 amps. I would replace the blower motor and use a 20 amp fuse.
    demet

  10. #10
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    I have a 20A fuse installed (maybe 25a i dont remeber). I've recently replaced the resistor. I think my next step is just inspecting the motor.
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  11. #11
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    moroza is offline MORΩN ΛABIA BMW CCA Member
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    Electric motors commonly draw a lot more current when starting than when running.

  12. #12
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    FWIW, the symptoms when mine started to crap out were just the whirring noise, and couple of days later blowing the 20A fuse (twice). Turned out to be the motor.

  13. #13
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    Quote Originally Posted by drewusmaximus View Post
    I have the exact same problem. I tried putting in a 20A fuse but, the blower wouldn't start. I checked the fuse and the fuse was blown. I put the 30A fuse back on and it started up again. I do get the light burning smell from time to time.I turn off the heat as soon as I smell it. I'll try another 20A fuse again but, I don't think the fuse will hold and I'm not sure why.
    The motor is very likely clogged with debris and is drawing too much power to try and turn. You'll have to remove the motor and clean out the area, unless you want to be really warm for winter...

  14. #14
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    Fuses don't blow just for the fun of it. Suggest you buy a new fan assembly and replace it. Peace of mind. No doubts. No carbeque.

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