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Big Voltage Drops While In Use

Discussion in 'Meyer / Diamond Products Discussion' started by CP Paul, Feb 1, 2011.

  1. CP Paul

    CP Paul Member
    Messages: 99

    I have big voltage drops while operating the plow, 7 1/2 E46, even after it is warmed up!

    I take good care of the plow, change the hydraulic fluid frequently...etc, etc.
    I use dielectric compound of all electrical connections, including the battery.
    I've just changed the alternator, just added a second new 875 CCA battery and still the gauge (mechanic verified) drops to 10 VDC when in use.

    The lights dimmed a lot before the second battery and still does somewhat but not as bad.

    Plow works great (when warmed up) and the new(used) TouchPad I put on instead of the old SlickStick makes 12 hrs of plowing a lot easier.

    Anyone got any ideas as to why this happens? Thought I thought of everything....

    Paul tymusic :drinkup:
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Poor connection between the pump motor and battery causing high resistance, or a worn out motor. An amp draw test will tell you if it's drawing an excessive amount of amperage.
  3. CP Paul

    CP Paul Member
    Messages: 99

    Was starting to suspect the pump motor, even though it seems to work fine.

    Has someone got the test set/method up to check how much the motor is drawing and...how much amperage it should be drawing?

    Thanks B & B...
  4. sefh

    sefh Senior Member
    Messages: 436

    Check your ground and make sure there is not rust building up on it. That was cause a resistance and make it draw more amps.
  5. Bashby

    Bashby Senior Member
    Messages: 228

    How can higher resistance cause it to draw more amperage? Everything I've been taught says the opposite.
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    If you have access to a clamp on DC amp meter they work well. If not then try a local parts store for the test. Simply tell them you want an on vehicle starter amp test done, works the same way for a pump motor. 230 amp against the pump relief is about as high as you want to see it. Any more than that it's just eating current unnecessarily.

    Note: be sure all your connections are 100% FIRST. A poor connection will skew any amp test results.
    Last edited: Feb 2, 2011
  7. CP Paul

    CP Paul Member
    Messages: 99

    .....We had a mother of a storm here.......man!

    Once again B & B, your a life saver! I'll check to be sure the ground on the pump is still good.
    Thought of the grounding problem first, just not the pump. Removed to truck ground on block, sanded, cleaned and dielectric compounded it...and that wasn't it.

    I'll check to see how many amps the motor is drawing and redo the ground on the motor too...first.
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    If your plow ground cable is on the engine get it off there and move it directly to the negative battery terminal. Grounding anywhere but directly to the battery creates it's own set of issues. Poor plow performance is the minor one, damaged truck side electrical components is the major one.

    Can't stress it enough....never never ground a plow anywhere but to the battery.
  9. swa136

    swa136 Senior Member
    Messages: 149

    Is it OK to ground to the batt cable where it connects to the block? That's grounding to the batt in a round about way isn't it?
  10. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Afraid not Sean, because now you're depending on that single cable to ground not only everything on the truck...but the plow also and most OEM cables are only adequate to supply the current demands of the truck let alone another 200 amp the plow will consume. Even with a cable upgrade it's far from ideal. It needs to be directly on the battery.
  11. CP Paul

    CP Paul Member
    Messages: 99

    Actually I meant that I re-did the ground for the truck. From the battery to the block. Just to make sure that the battery itself a a perfect ground.