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Strange headlight issue chevy fisher mm1

Discussion in 'Fisher Engineering Discussion' started by livetoplow, Nov 1, 2014.

  1. livetoplow

    livetoplow Member
    Messages: 49

    Hi I have a 2002 Dmax and have a strange headlight issue that I can not seem to fix. I have read through this as well as other forums and asked many people local with no answer so I'm hoping someone has had this issue or has the answer

    When I turn on my headlights, they work fine. I can switch from low beam to high beam no issues. Now when I go to drive I will occasionally switch and the high beam indicator will come on the dash and then both high beams and low beams are on at the same time and cause my fogs to shut off. When it acts up I can not switch it with the high beam indicator. When I do it will just turn off the low beams but highs will stay on. I have taken out the headlights, checked fuses, switched relays and grabbed every wire that I could and shook it to cause it to switch so I can know where the issue lies. Nothing changes. Now when I close the hood though you can see the headlight flicker and even sometimes clears it up and the headlights go back to normal.

    I even tried to go to a local chevy dealership and suck up the cost but was turned away by them as they stated my truck is too old and they don't work on Chevys that old. Never heard of that one. I told them your a damn chevy dealership. I want to bring in my chevy. So you all are my last place to turn. I do have a fisher mm2 plow setup in the truck also. I have been told by others it is most likely a fisher wire issue. I know you guys know your stuff when it comes to plows. I am willing to pay to have someone look at it. Many of the fisher dealers want to hose me for tons of cash to just look at it

    Thanks for any and all help

    Keith
     
  2. ss502gmc

    ss502gmc Senior Member
    Messages: 473

    Sounds to me like you have a shorted wire inside your lighting plug, you may not be able to see it as it can be inside the molded rubber. The hard part is determining whether it's the truck side or plow side harness. If you know someone with the same plow, hook it up plow and see if you can get it to act up if it doesn't there's your problem but if it still does it, replace your truck side harness. That's the best I can tell ya, I'm no expert on wire testing but it's what I would do in a jam. Good luck! Just realized that it seems like your talking about the truck headlights? With no plow connected? If so the problem may be in the isolation module in which case your better off waiting for a reply from someone that knows them better than me, but still could be in your light harness like I was saying because if 2 wires are making contact it can be sending false signals back to the ISO module
     
    Last edited: Nov 1, 2014
  3. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,966

    First, call that dealer back, get the name of the guy that said that. Then call back and talk to the G.M and tell them that, also mention that your out of warranty and paying book time.
    Ok rant over.....

    What do you mean, you go from drive but switch to the multifunction switch?
     
  4. livetoplow

    livetoplow Member
    Messages: 49

    Yeah I was a little pissed off being told by a GM dealership that they do not want my business. I told them I have no problem paying the $90 hr rate just want it fixed as winter is getting closer. We have slush mix right now in RI. They said the truck is too old. It's a 2002 :dizzy:

    The headlights are strange just started doing it. It will do it out of park just noticed it one day was fine idling in the driveway then when I put it into drive they acted up that day. Could have been just a fluke. But the problem is, they will act up out of no where. The high beam indicator in the truck comes on and when it happens both high and low beams are on and fog lights shut off. Then if I hit the high beam switch, just the lows will go off but highs stay on. Now I have tugged and grabbed on every harness and wire I can get to. Nothing changed it. Now usually when I close the hood though. It will flicker like it is clearing itself or sometimes it will actually fix itself and go back to normal.

    Just started doing it. I can't figure it out to save my life. Had a fisher dealer tell me $95 an hr and has no clue how long to figure it out which is crazy. Just hoping I can find the solution on forums.
     
  5. livetoplow

    livetoplow Member
    Messages: 49

    How would I determine if I had a bad ISO box. Also would I notice the bad connection inside the plug. I've looked at them and didnt see anything out of place. Also thought the ISO box myself. It's a 4port box with a 3 plug setup. I tapped on the box seeing if that might be it but nothing. Get a reaction usually when I close the hood though
     
  6. ss502gmc

    ss502gmc Senior Member
    Messages: 473

    im just thinking the iso module because that's really the only thing where factory meets fisher, I'd shake the **** outta the ISO module to see if it does anything related to the problem. Especially if it affects it shutting the hood. When you put truck in drive it turns the daytime running lights on which is what I'm thinking has something to do with it. The fog lights are supposed to shutoff when you turn hi beams on also. Maybe try beating on your steering column to get it to do it? I have basically the same truck so I'm trying to think what I'd do. My ISO is mounted right next to the hood spring which is why I mentioned. Also you usually can't tell in my exp that the plug is messed up, gotta check at the base of the pins where they go into the rubber but mine always looked great even tho they were junk
     
    Last edited: Nov 2, 2014
  7. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,966

    Try taking the plow set up out of the equation. Plug the factory trk light harness.back in and see what happens.