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Thread: How to test LWB fresh air blower?

  1. #1
    Serial old car rescuer Arne's Avatar
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    How to test LWB fresh air blower?

    Looking at another of the non-working secondary systems - the fresh air blower.

    The blower motor itself works fine (after some oil on the bearing felt). I can jump it with 12v and it spins like crazy.

    But I can't make it work with the switch on the vent panel. The fuse is good, and at the 4-post plug on the blower hosing, one is hot (12v), and each of the other 3 show a ground in one of the 3 switch speeds.

    I've determined that the blower motor is seeing the 12v side, but nothing happens in any of the 3 speed positions, so I'm wondering if the resistor pack in these cars is a common problem. Is there any way to test this stuff?
    - Arne

    Mostly done
    - 1972 911T coupe, Silver Metallic, Fuchs, Appearance Group, F&R sway bars, factory installed Frankfurt. Soon to regain factory A/C.
    Sold - 1984 911 Carrera coupe, Chiffon white; 1973 914 2.0, Saturn Yellow; 1984 944, Silver Metallic

  2. #2
    Senior Member
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    I would look at the slide switch in the dash. It accumulates a large amount of crud and corrosion and might not be making proper contact with the lever. Get some 0000 steel wool and clean the contact area and check that there is good contact between the two.

    Regards

    Jim

  3. #3
    Hi Arne, did you ever determine what your issue was? I’m having similar problems with my blower as well.

    Thanks,
    Rick

  4. #4
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    Hi, I had a similar problem and it turned out to be the resistor pack: inside, you will also find some thermal protection switches (bimetal type). I suppose they are there to protect the system in case one of the resistances starts to go nuclear and melt or cause a fire. These switches are somewhat delicate and need to make good contact when cold, otherwise, no current and no air. I found I picture of mine in case it helps. You can see the bimetal strip just below the spring and, on the left, the metal contact that needs to happen.

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    1972 Targa 911S (one day), silver gray (maybe), member 3337

  5. #5
    Thank you Florio for the response and picture. A friend of mine (also a member here - tom1394racing) is testing it for me. We talked about the resistor pack. I wouldn’t be surprised if that ends up being the problem.

    Rick

  6. #6
    For what it is worth, had same issue. Solution was same as Jim suggested. Contact cleaner and very fine steel wool. Was a bit to access properly.

  7. #7
    Serial old car rescuer Arne's Avatar
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    Quote Originally Posted by rac390 View Post
    Hi Arne, did you ever determine what your issue was? I’m having similar problems with my blower as well.

    Thanks,
    Rick
    Mine was the slide switch, as suggested by Jim in the first reply above.
    - Arne

    Mostly done
    - 1972 911T coupe, Silver Metallic, Fuchs, Appearance Group, F&R sway bars, factory installed Frankfurt. Soon to regain factory A/C.
    Sold - 1984 911 Carrera coupe, Chiffon white; 1973 914 2.0, Saturn Yellow; 1984 944, Silver Metallic

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