99 FLD120. Wiper switch problem

Discussion in 'Freightliner Forum' started by xsetra, May 29, 2022.

  1. xsetra

    xsetra Road Train Member

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    This started couple months ago. Driving and needed wipers on. Turned switch on. Wiper motor didn't come on. Turned switch on off a few times. While idling on off ramp. Wiper motor didn't come on.
    I checked all the fuses in the panel, none were bad.

    I hot wired the switch to get home.

    I replaced the ignition switch. That didn't fix it. Then I replaced the wiper switch that didn't fix the problem.

    Sometimes when I start the truck the wipers work.
    Now before I start the truck I turn the wiper switch on, then I turn the key on. If the wipers move I start the truck. If they don't move, I'll turn the key off and on until the wipers move, then I'll start the truck.

    Sometimes I have to key on/off several times before I start the truck.

    The wipers will continue working using the switch until I turn the truck off.

    My concern is the wiper motor not coming on at some point.
    What electrical thingamajig is between the ignition switch and the wiper control switch?

    I guess it's a bad relay, I can't read any labels on the relays. Can someone show me which relay is for the wipers.
    Thanks.
     
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  2. Big Road Skateboard

    Big Road Skateboard Road Train Member

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    Surely you verified no power to motor? Cause it sounds like a bad motor.
     
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  3. xsetra

    xsetra Road Train Member

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    The power problem is the feed to the wiper switch.
    When the power is coming out of wiper switch the motor works.
     
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  4. Tigerfishinc

    Tigerfishinc Light Load Member

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    If the wiper has a wipe sensor mounted on the windshield- change that sensor. Sounds exactly like a rain sensor issue
     
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  5. Rideandrepair

    Rideandrepair Road Train Member

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    Are you sure? Did you use a test light at the plug for the motor? Maybe you turning switch on and off and turning switch on first, then ignition on and off is doing the same thing either way. Putting power to the motor. Maybe the motor itself is the intermittent problem. Reminds Me of a Dodge Dart that would only start holding the key on, while shifting from d to n to r to n to d etc. till it grabbed. The Owner was baffled. Neutral safety switch was bad.
     
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  6. xsetra

    xsetra Road Train Member

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    Thanks for the replies.
    The wiper motor coming on, Only works with the wiper dash switch having power out.

    The power from the ignition switch into the dash switch is the problem.

    When I hotwire direct from fuse panel to dash switch input the wiper motor works every time.

    Is there a in line fuse or a relay in the circuit somewhere?

    I suppose the dash switch I replaced could be bad same as the first. I'll try a third switch.
    It doesn't act like a wiring problem because I can get the wiper to activate just sitting and toggle the switches.
     
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  7. xsetra

    xsetra Road Train Member

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    No sensor.
     
  8. Tigerfishinc

    Tigerfishinc Light Load Member

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    Get a probe 3 -
    With ignition on - test if you’re getting a current at wiper switch. If so - then it’s working
    If no power - check the ground for wiper switch
    With ignition off - apply power to wiper switch and see if wiper works
    Apply ground to wiper switch see if it works
     
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  9. xsetra

    xsetra Road Train Member

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    If I turn ignition switch on and the wiper motor doesn't come on with the dash switch. I have turned dash switch on and off 30 times without the wiper motor coming on. BUT if I turn the ignition switch off and on again (it has taken up to 6 times) to get power to the dash switch to power the wiper motor.

    As long as I don't turn the ignition switch off, the wiper switch operates normal. Couple days between starts.

    I can try a different wiper motor. I don't think the motor is the problem.
     
    Last edited: May 30, 2022
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  10. xsetra

    xsetra Road Train Member

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    That is the problem. Power to the dash switch.
     
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