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Headlight issue with port #3 on 26400 module

Discussion in 'Fisher Engineering Discussion' started by skoalcowboi00, Jan 3, 2012.

  1. skoalcowboi00

    skoalcowboi00 Junior Member
    from PA
    Messages: 3

    This is on the truck Ok I have read many posts that sound similar to my problem but I have done many things including changing the configuration from b-c and b-a with no luck or change, making a test plug to check port #3 and I have power coming in on the blue wire but no power going back out the orange wire for low beams on the drivers side I switched #4 plug (passenger side lights) to # 3 and then there is no low beams on the passenger side. I have traced both wiring harnesses for broken wires and find nothing. High beams do work fine on both sides. I have hooked the headlights up directly to the dodge factory headlight harness and everything works fine. I have HB1-9004 bulbs and I have checked fisher website and I have my wires configured right. All my fuses are good. I have a 1995 dodge 2500 with 8' mm It is 4 port isolation module with 3 wires to plow and the light plug is 3 pin. Bottom of the line is on #3 port I am not getting power coming back out for low beam lights. Is the module bad or am I missing something? thank you
  2. Lone136

    Lone136 Senior Member
    Messages: 108

    There was a long tread on this in Western plow treads, But in was more in the line of the lows beams being very dim. I also have a Fisher and they are dim, but are working non the less. It sounds like to me your # 3 port on your module has gone bad since you can hook up the lights to your truck and they work just fine. I think this is why Fisher and Western wait to the 3 port module. I do think I have a used 4 port at work
  3. skoalcowboi00

    skoalcowboi00 Junior Member
    from PA
    Messages: 3

    Mine have been dim for 3 years and I finally spent the last 3 days trying to figure it out and found out I had to switch the blue wire with the yellow wire in both headlight harnesses from A to J and vice versus now I have one awesome low beam on passenger side and 2 awesome highs again. Gotta be something I am missing or a bad module I guess.
  4. Lone136

    Lone136 Senior Member
    Messages: 108

    I had so many problems with mine since I wait the the module setup. I had the old relay and everything was just fine, but live and learn the hard way I guess. I think I may just buy a new one and see if that helps. If not, then I just have a new one if the one I have now stops working on a snow night from hell......lol
  5. Arc Burn

    Arc Burn PlowSite.com Addict
    Messages: 1,141

    Bad Iso Mod,I've only seen one go bad in my shop and it was a 29760 with 1 low beam out (3 port)
    Last edited: Jan 4, 2012
  6. No Shoes

    No Shoes Junior Member
    Messages: 2

    I came across this post doing many searches after having the same issue on a 2000 GMC.
    I took the plow off a 1999 Chevrolet Tahoe. Almost identical headlight bulb setup. Wired everything up and had no port 3, driver side high or low, (could plug into 4 and seemed ok) also no plow lights.
    I even bought another 26400 thinking it could have got damaged somehow.
    Found a used one on ebay, same results. I found it impossible that I had 2 bad modules doing the same thing??
    Well after days of testing circuits/wires and getting nowhere, I read somewhere that someone had swapped polarity to their lights to the input of the module. What really threw me off was I had to swap polarity to the side that was working (passenger side) in order for it to work properly... go figure?
    Out of curiosity along the way I split one open to see what's inside that can go wrong... and not much! Just a series of relays and diodes, actually quite robust.
    Also had to swap configuration plug from A-B to B-C.
    Lights are now working as they should.
    Hope this helps someone out there banging their head against the wall. It sure could've saved me a lot of frustration and a little $.
  7. jday53

    jday53 Junior Member
    Messages: 8

    Mine is doing the same thing. I took one module off one truck to try it on an other and when I put it back it wasn't working. No drivers low beam. Everything worked perfectly before only thing I did was unhook module and rehook it back up.
  8. BigCountryBCE

    BigCountryBCE Junior Member
    Messages: 21

    I am having basically the same problem, I have a MM2 EZV. I just changed the plow lights to intensifires. On the old lights and the new ones I didn't have low beams on driver side. I tried changing the A/B B/C ports on the isolation module. (3 port) I reversed the wire harness on the low beam driver side and now all lights work correctly on high beam but on low beam all plow and front truck lights flash. The C port on the isolation module keeps clicking. Port C clicks with the wires from port c and port b. I am thinking the module is bad?