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lights not switching over

Discussion in 'Commercial Snow Removal' started by choiceland, Nov 11, 2003.

  1. choiceland

    choiceland Junior Member
    from WI
    Messages: 6

    I have a 1991 Chevy 2500 with a western unimount and the head lights do not switch over to the plow lights. I tried two new relays and that did nothing. Any ideas of what else I can check before I bring it in?
  2. Adams plowing

    Adams plowing Senior Member
    Messages: 195

    have you tried bypassing the switch and useing a jumper wire to the side of the relay that the switch would normaly power to activate the lights. if it works the switch is bad... if not then you have another problem also you can use a volt meter or test lite to check for power coming into or out of the relays.
  3. Plow Meister

    Plow Meister PlowSite.com Addict
    Messages: 1,174

    I would have guessed a bad relay. Since you have already replaced it, move on to the next possibility. How about the relay for rhe main truck brights. Do you have brights without the plow on?
    Last edited: Nov 11, 2003
  4. Dieselman19

    Dieselman19 Senior Member
    Messages: 141

    The same thing happened to me i ended up haveing a broken wire in the harness, so i bypassed the wire and got them to work, but the next time i went to use the plow it would not drop, i had another broken wire, i was confused becuase they where both brock under the hood and it was in the black mess, but that was my problem and it sounds like yours also
  5. Crash935

    Crash935 2000 Club Member
    Messages: 2,377

    Since your pretty sure the relays are ok, check to make sure your getting power from your masker lights by checking for power on the brown wire at both relays (marker lights need to be on), Check for ground on the black/orange wires that are opposite the brown wires, and check your 9-pin connector at the grill for 9 pins. Let me know what you find, may take a little time but we can solve this one.
  6. choiceland

    choiceland Junior Member
    from WI
    Messages: 6

    thank you all. You guys are fast!! I will check that stuff and get back to you.
  7. Dieselman19

    Dieselman19 Senior Member
    Messages: 141

    The problem is the marker lights worked on mine, it is becuase the lost the ground wire that is the one that was broken on mine, it grounds out the truck lights and fires the plow lights the only way to test this to put a continuaty test and see if you have continuaty through each wire on the 9 pin harness
  8. Mac

    Mac Member
    Messages: 77

    Make sure your new relays are the right ones. They must be a relay with a N.O (normally open) and a N.C (normally closed) contact. But if you got to from the dealer then you should be o.k.
  9. Brian Simmons

    Brian Simmons PlowSite.com - Sponsor
    Messages: 196

    need a little more info. what kind of lighting do you have? Toggle switch or the 9-pin setup that switches over automatically when the harnesses are plugged together. Do the truck lights shut off when the plugs are plugged together? The way the relays work is you should have a brown wire from the parking light tap that provides 12 volts to the relays and there will be a black wire with a orange tracer that provides ground when the plow is attached. If the plow is hooked up and there is no plow lights check to see that you have 12 volts at the brown wires. If you do then you need to check for ground at the black and orange wire. Make sure you remove the ground wire off of the relays before checking for ground as you may get a false reading.
  10. szorno

    szorno Senior Member
    Messages: 308

    One other thought. We had a little corrosion in the 9 pin connectors. Make sure they are clean and corrosion free before you get too carried away patching and replacing.;)