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Headlight Problem

Discussion in 'Truck & Equipment Repair' started by ajquint, Dec 23, 2012.

  1. ajquint

    ajquint Junior Member
    Messages: 10

    2005 Dodge with Fisher MM2 LD. I have plow headlights but when I disconnect, passenger side truck headlight not working. I checked all the connections and can't figure out if it's the c port in the isolation module or in the wiring, which looks fine. I'm new to this...thanks.
     
  2. ajquint

    ajquint Junior Member
    Messages: 10

    I read a bunch of other posts and checked as many of the likely culprits that I saw, i.e. high intensity bulbs, dirty plugs, grounds, etc. Just trying to avoid buying new isolation module if that is not the issue.
     
  3. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,977

    Ok. You need to ck a few things. Ck for pwr at the headlight plugs,,,tk and plow are you loosing it at the tk side wiring or plow side wiring. You prob have pwr into the ISO,,,so you gotta see if you have pwr out for the tk lights also did you ck fishers website for the wiring diags??
     
  4. ajquint

    ajquint Junior Member
    Messages: 10

    I have power on the truck side, when I got the truck they had bypassed the plow/iso and went straight to the tk headlight and that worked fine (but the plow hdlt on that side would not work of course). I did find the schematic, but I am not known for my electrical prowess. Could I swap the plugs at the b and c ports at the 3 port iso and expect the problem to be the same but on opposite side? I was thinking if I did that I would know the iso was the problem, but I don't want to burn anything up. Thanks, sorry if I am confusing the issue...
     
  5. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,977

    You can switch the port plugs. Now here's what you need to ck plug c....letter e, low beam out. And pins j & k for gnds that's output to the tk lights
     
  6. ajquint

    ajquint Junior Member
    Messages: 10

    No power at letter e, no ground at k. J was grounded and the high beam pin was weak...
     
  7. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,977

    Hummmm. Ok did you switch a ans b port
     
  8. ajquint

    ajquint Junior Member
    Messages: 10

    No I didn't. That would be the b and c ports for the head lights I think and I see the DRL is on one side where the other has park lamps so I am short a pin on the b port
     
  9. ajquint

    ajquint Junior Member
    Messages: 10

    I did try swapping b and c and that put power to the truck headlight on the affected side but I lost the plow lights and some other goofy stuff.
     
  10. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,977

    Hummm. Did you test the plug at the ISO with it plugged in? Make sure that the headlight plugs are on the right way. They can be flipped you know.
     
  11. ajquint

    ajquint Junior Member
    Messages: 10

    I tried the plugs both ways a while ago, but they are flipped and matching the bulb number now. I did the test with plug in and was not getting any results so I tested it unplugged to get the results I gave you. Maybe I was doing it wrong, I removed the grey plastic piece and put the probe down where the wires go into the plug, looked like brass. Thanks, merry Christmas.
     
  12. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,977

    well as far as the plugs at the lights,,,they and flipable. you have to install them per your tks lighting circuit, switched pwr, or gnd. its the a or b on the plow plug.. the plugs at the iso need to cked while they are plugged in. and the lights "on" remember you have pwr to your lights coming into the iso box, then either out to the tk lights or plow lights,and it sends out pwr and gnd. it changes from tk to plow via a gnd wire. at the grill/plow motor.
     
  13. clark lawn

    clark lawn PlowSite.com Addict
    from NE ohio
    Messages: 1,233

    Dumb question bit did you check the bulb? Have seen more than one person rip out a whole wiring harness because of a bad bulb
     
  14. ajquint

    ajquint Junior Member
    Messages: 10

    I would not be beyond doing that,lol, but if I bypass the iso the trucks good, when I have the harness plugged in (I hope correctly) the plow is all good. Just can't get them both at the same time. I still am not having any luck with the tester on the port when it is plugged in, gonna take another run at it after the festivities today. Thanks again to all...
     
  15. sectlandscaping

    sectlandscaping Senior Member
    Messages: 314

    I just had this problem on my chevy. Drivers side wouldnt work with harness plugged in. I ran a ground from the lighting harness to another ground behind the headlight. That fixed the headlight. Then I ran a ground from the plow light to the marker lights and that fixed plow side.
     
  16. ajquint

    ajquint Junior Member
    Messages: 10

    When you ran the ground wires, did you tap into the wires on the harness or from the plug? Sorry if that's a dumb question, I don't trust myself much with wiring. The wires are clearly marked, so that sounds like something I could try easy enough. Thanks.
     
  17. ajquint

    ajquint Junior Member
    Messages: 10

    Well, just to put a bow on it, I should have went with my gut this time. It was the isolation module like I originally thought. Thanks again to everyone who tried to help.
     
  18. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,977

    Thx for the update on the fix. Glad you did get it fixed in the end