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Voltage drop when engaging lift motor.

Discussion in 'Truck & Equipment Repair' started by musicars, Oct 31, 2015.

  1. musicars

    musicars Junior Member
    Messages: 20

    I have '94 F-250 with an older Western Pro Plow. Since I bought this I have had a significant voltage drop whenever the lift motor is engaged. I've searched this site and used the tips I've found but so far no improvement. I have installed a new lift motor, added a heavier cable between the alternator and the battery, added an extra ground from the battery to the chassis, and installed a heavier duty alternator.

    The factory volt meter drops to 8-10 volts when I hit the switch. It is so bad that if I go to lift the blade while I am backing up the engine starts missing (real bad when cold).

    I recently decided to put heavier cables to the lift motor and came across something strange. I took the cables off to the lift motor so I could measure them and when I started the truck up the battery light came on. After checking a bunch of stuff and not finding a problem I put the cables back on and the light went out. The only cables removed were the cables that run the lift motor. I can't help but think this has something to do with the drain. The controller was connected at the time but was not engaged. I turned the controller on and off but that made no impact on the battery light being on.

    I brought it to a mechanic for another issue. When I asked about this one they could not give me an answer other that "maybe the battery was low". The battery is fine and that would not explain this weird thing with the battery light coming on when I removed the cables.

    Any thoughts?
  2. Brian Young

    Brian Young PlowSite Veteran
    Messages: 3,394

    How much reserve capacity does you battery have, it should say on the sticker. Whats the alternator putting out, those older plows draw a lot of amps when going up. Get a volt meter and check actual numbers, I wouldn't go by the battery meter in the truck. On a volt meter it should be showing right around 14.4 when the truck is running.
    Last edited: Oct 31, 2015
  3. Randall Ave

    Randall Ave PlowSite Veteran
    Messages: 3,593

    Clean all the ground connections, motor to frame. Frame to body, etc. How did you test your battery and charging system?
  4. seville009

    seville009 Senior Member
    from CNY
    Messages: 877

  5. FredG

    FredG PlowSite Veteran
    Messages: 3,413

    On the older western could it be he needs a dual battery set up? Electrical is not my thing. I'm having some trouble myself on the older back up trucks. Everything worked when parked last season.

    Just a lot of clicking, Solenoid has been changed.
  6. musicars

    musicars Junior Member
    Messages: 20

    The battery is an Interstate 85 month with 1000 cranking amps and 850 cold cranking amps. There is no rating for the reserve anywhere on the battery. I have tried a couple different large batteries with the same results.

    The volt meter in the truck is pretty close to the numbers I get with my digital meter. While the actual numbers are not exact the drop in voltage is correct. It's around 9.8 under load from the lift motor and 14.4 at idle using the digital VOM.

    I've checked most connections The only one I currently question is the engine to ground. I've added a HD ground cable from the battery to the frame. I plan on adding one from the battery to the engine as I'm not even sure where the factory one is attached. It's buried somewhere behind the the accessories.

    I was planning on replacing the skinny Western factory cables anyway. That's how I found the weird thing with the battery light coming on when I removed those cables. I still think that is significant. It makes me think the juice is having problems going the path it is suppose to go or there is some kind of short. Just not sure exactly what to look for. I hate replacing things until it is fixed. I would like to know why first?

    Thanks for tips.
  7. seville009

    seville009 Senior Member
    from CNY
    Messages: 877

    If you follow the links in my posts above, when I had a similar issue, the Western dealer told me that Western had a design flaw prior to 2009. Whether that is true or not, I don't know, but it did fix my electrical issues. This was a different dealer than the one that installed the plow in 2007.