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light problem on mvpp

Discussion in 'Western Plows Discussion' started by dancing bear, Jan 15, 2016.

  1. dancing bear

    dancing bear Junior Member
    Messages: 20

    I have a MVP with the two plug harness ,three port module its on a 98 GMC the problem I'm having is the plow light on the passenger side is out ,both high and low beams.truck has DRL lights, while plowing the light went out and a buzzing sound is coming from behind the dash,if I change the beam to low the buzzing stops but still no light on the right side.any ideas on where to start looking
     
  2. Philbilly2

    Philbilly2 2000 Club Member
    Messages: 2,557

    Is the buzzing under dash (inside cab) or under the hood against the fire wall?
     
  3. dancing bear

    dancing bear Junior Member
    Messages: 20

    It sounds like its behind the dash , from under the hood I can hear it behind the firewall
     
  4. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    I am a bit confused with your description of the plow. "I have a MVP with the two plug harness ,three port module." If it's a two plug / three port it must be an MVP+ with the multiplex four pin controller.

    My suspicions would take me to the isolation module first. But it would be nice to know exactly what the source of the buzzing is. At our shop we have an isolation module tester, perhaps call your local dealer and see if they have one and how much they would nail you to test one.
     
  5. dancing bear

    dancing bear Junior Member
    Messages: 20

    Yes sorry for the confusion it is a MVP+ I will source the buzzing noise this morning
     
  6. Randall Ave

    Randall Ave PlowSite.com Addict
    Messages: 1,950

    If plow is off, is noise gone and do the truck lights work?
     
  7. dancing bear

    dancing bear Junior Member
    Messages: 20

    OK with the plow unplugged truck lights work fine,with the plow plugged in the right side plow light is out on the bright with no buzzing low beam is out and it buzzes this is on the DLR, with headlight switch on the light is out both beams but the buzzing is reversed no buzzing on low , high it buzzes,side note here the wire for the DLR was never hooked up and everything worked fine for two years
     
  8. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    Still sounds like an isolation module problem to me. But you still didn't say what exactly is buzzing? Is it under the dash or in the engine compartment? Some trucks are so packed full of engine that the isolation module is stuffed behind a headlight or down around the master cylinder. Just make it buzz and then follow the noise.....
     
  9. dancing bear

    dancing bear Junior Member
    Messages: 20

    I couldn't find the source ,it is behind the instrument cluster, I know it is not the modual buzzing it is fastened to the lid of the underhood fuse panel out in the open
     
  10. Randall Ave

    Randall Ave PlowSite.com Addict
    Messages: 1,950

    Be specific, with plow hooked up. What works, what doesn't work.
     
  11. dancing bear

    dancing bear Junior Member
    Messages: 20

    With plow hooked up plow works fine no right side headlight left one works when I change from high to low beam and buzzing starts the left light gets dim(DRL) headlight switch on it buzzes on high beam and left light gets dim .I will have the dealer check the insulation module Mishnick suggested on Monday. I never hooked up the wire for the DRl when I installed the plow because they worked on the plow without it.does it sound like that may have caused the problem?this plow was new in 2013 and has worked fine till now
     
  12. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    If the plow worked at one time it's not a matter of being miss-wired, it's a matter of component failure. I have installed hundreds of plows and I know it doesn't matter if the DRL wire is connected or not. Forget about that.

    It would be nice to know what that buzzing thing is but whatever it is I still suspect the isolation module is at fault and causing this buzz as a symptom rather than a cause. Eliminate the isolation module and then we can move on to other possibilities.
     
  13. Philbilly2

    Philbilly2 2000 Club Member
    Messages: 2,557

    Dancing Bear,

    What Nick and I are trying to figure out here to get you on the right track:

    Is the buzzing from the isolation box under the hood (commonly up near the firewall) - this leads us to relay failure inside the isolation box (my guess too)

    OR

    is it coming from something inside the cab under the dash - which would lead us to a truck side HI/LOW switch, headlight switch, or a truck side headlight relay. (lots of small issues here that can possibly cause something.

    This is the info you really need to get for us. Once we know which item we need to diagnose, it is a pretty simple process - either direction. Hate to have you throw money at the wrong part.
     
  14. Philbilly2

    Philbilly2 2000 Club Member
    Messages: 2,557

    See if it is this that is buzzing. Yours should look very similar this is from a 2000 3500 you might have two if you have factory fog lights

    This is your DRL Relay on your truck - under dash, down by the parking brake pedal.

    DRL Relay.jpg
     
  15. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    As Philby2 is saying.... It's either a truck problem or isolation module... Possibly a wiring problem. But you must break it down to plow or truck. You could disconnect the western headlight harness from the truck headlight plugs to put it back to factory. Then test all the lights. If buzz and problems continue its a truck problem. If trouble goes away focus on isolation module / western headlight harness.
     
  16. dancing bear

    dancing bear Junior Member
    Messages: 20

    Well I got the module tested and it was good so the parts guy sent me home with a truck side harness to try, before I changed it I pulled out the bulb again and looked it over ,the bulb is not burnt out but I took it out of the wire plug this time and tried the lights ,no more buzzing so for grins I put it in the left side and it worked so I put the left bulb in the right side and it worked with no buzzing,all lights working so I dont know what the problem was or is but for the time being it's working I guess only time will tell if it fails again .
     
  17. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    "parts guy sent me home with a truck side harness to try," Which cable? Headlight harness? Part #?

    Switching the bulbs corrected the problem???? Which bulb did you swap, plow or truck?
     
  18. Philbilly2

    Philbilly2 2000 Club Member
    Messages: 2,557

    What??? You switched the drivers and curbs side bulbs and the issue is gone... now that is a first! [​IMG]
     
  19. dancing bear

    dancing bear Junior Member
    Messages: 20

    Yes just switched the bulbs from side to side and it works now ,the harness was the the one from port C on module to plow but I never tried it after they started working. I feel like I deserve a ( turn the switch on stupid) remark, so with that said thanks for allthe input and help I'll let you know if it fails again