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Thread: Fan Speed 3 Not Working

  1. #1
    Senior Member BladeBronson's Avatar
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    Fan Speed 3 Not Working

    What would cause only fan speed 3 to stop working? Fan speed 4 works and is on the same fuse. Is it the switch itself?

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    Delorean Guru
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    Quote Originally Posted by BladeBronson View Post
    What would cause only fan speed 3 to stop working? Fan speed 4 works and is on the same fuse. Is it the switch itself?
    Wire not connected to the fan speed switch
    Bad or missing relay or connector backed out in the block
    Some other wiring problem. Speeds 3 and 4 each have their own relay.
    David Teitelbaum

  3. #3
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Could be the switch but most likely is the relay esp if it's an original.

    Troublshooting chart for fan:

    Lost all speeds - likely the fuse or the switch.

    Lost speeds 1, or 1 and 2, or 1 and 2 and 3 but not 4 - resistor pack

    Lost 3 and 4 but not one and two - circuit breaker.

    Or any of the associated wiring in all cases.

    Lost speed 3 or 4 only - relay or switch.
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

  4. #4
    EFI'd dn010's Avatar
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    Quote Originally Posted by DMCMW Dave View Post

    Lost speeds 1, or 1 and 2, or 1 and 2 and 3 but not 4 - resistor pack
    Where is this located? Losing all but 4 is my exact problem.
    -----Dan B.

  5. #5
    Senior Member BABIS's Avatar
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    Quote Originally Posted by dn010 View Post
    Where is this located? Losing all but 4 is my exact problem.
    on the bottom side of the evap. box, near to the blower motor..
    VIN 4502

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    Senior Member BladeBronson's Avatar
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    Man, leave it to Dave to come through with encyclopedic accuracy. Thanks!

    I opened up the panel to check the 3rd speed relay last night, but found that all speeds were working. A few weeks ago, I thought that the 3rd speed wasn't working, but did when I checked the next day, so this seems to be an intermittent problem. My relays are metal with a diagonal red line going through them. I don't know if that indicates the type or age of the relay. Rob Grady inspected my car about a month ago and didn't have any notes about the relays, so I think they're probably up-to-date and correct.

    I'll check to see if there's a loose wire on the back of the switch.

  7. #7
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by BladeBronson View Post

    I'll check to see if there's a loose wire on the back of the switch.
    Unplug and remove the resistor pack. Nice thing is that you can tell if it is bad with a visual inspection (a bad one will be rusty and have a visibly broken wire inside), and the part is cheap.
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

  8. #8
    EFI'd dn010's Avatar
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    Wow, this whole time it was a $6 part! Thank you guys!

    Quote Originally Posted by BABIS View Post
    on the bottom side of the evap. box, near to the blower motor..
    -----Dan B.

  9. #9
    Senior Member BladeBronson's Avatar
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    Apologies for not reporting back sooner. The issue was loose wires at the resistor pack. I made sure they were all clean and firmly connected and I haven't had any problems since.

  10. #10
    Senior Member DMC-81's Avatar
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    Quote Originally Posted by DMCMW Dave View Post
    Could be the switch but most likely is the relay esp if it's an original.

    Troublshooting chart for fan:

    Lost all speeds - likely the fuse or the switch.

    Lost speeds 1, or 1 and 2, or 1 and 2 and 3 but not 4 - resistor pack

    Lost 3 and 4 but not one and two - circuit breaker.

    Or any of the associated wiring in all cases.

    Lost speed 3 or 4 only - relay or switch.
    So, I recently experienced the bolded scenario. I used this thread to troubleshoot (Thanks Dave S!).

    Sure enough, my old (original) resistor pack (DMC part number 101275) was the problem. The front resistor (speed #1) is deformed and broken:



    I got a new one:


    I noticed the new one (nor the parts I cross referenced) came with the original 1/8" foam gasket, so I decided to make one out of some closed foam 1/8" x 10mm wide self adhesive gasket material I had:


    This part is located next to the blower fan under the passenger side footwell, and is secured by 2 screws with a 7 mm hex socket head:



    Woo Hoo! Now cabin fan speeds 1-3 are working again. Easy Peasey.
    Last edited by DMC-81; 02-16-2019 at 09:35 PM.
    Dana

    1981 DeLorean DMC-12 (5 Speed, Gas Flap, Black Interior, Windshield Antenna, Dark Gray)
    Restored as "mostly correct, but with flaws corrected". Pictures and comments of my restoration are in the albums section on my profile.
    2006 Dodge Magnum R/T (D/D)
    2010 Camaro SS (Transformers Edition)

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