1. Welcome to PlowSite. Notice a fresh look and new features? It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

01 Chevy wiring problem

Discussion in 'Western Plows Discussion' started by 2005DMAX, Dec 27, 2014.

  1. 2005DMAX

    2005DMAX Junior Member
    Messages: 20

    I just installed an older 12 pin ultra-mount straight blade on a 2001 chevy 2500. I bought this plow new in 2004, but have had it on multiple trucks. When I plug the harness into the factory headlight wiring, the truck high and low beams both come on together. Without the harness connected to the truck wiring, the truck lights work fine. This all happens without the plow connected.

    I have been over and over the wiring and can't figure out what is causing this. Any ideas??
     
  2. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,975

    You need the relay adapter harness from western.
    Use the quick match and it should come up for the trk
     
  3. 2005DMAX

    2005DMAX Junior Member
    Messages: 20

    What does the relay harness adapter do? This is the harness with 6 relays. It came off of a previous truck of the same model and worked on it.
     
  4. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,975

    Oh it's not the Iso module set up then?
     
  5. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    Not twelve pin. That's a relay system

    I'd check for broken or corroded wires at each spade on the relays. Or possibly replace the relays. You've likely got a shorted wire or relay that's back-feeding the rest of the harness somewhere.
     
  6. 2005DMAX

    2005DMAX Junior Member
    Messages: 20

    I have replaced all of the relays and any bad connections.
     
  7. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

  8. Marlon

    Marlon Junior Member
    Messages: 10

    In addition to double checking each relay connection against the diagram on page 86(you mentioned that you changed the relays),you may want to search this site for information regarding the polarity of the pins on the headlight connectors themselves. Depending on what truck they came off of,the pins may be reversed.
     
  9. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    Previous truck may have been same model but different headlight setup.
     
  10. Western1

    Western1 Senior Member
    from MI.
    Messages: 679

    12 pin harness was used on the Chevys from 2003-2006. Your 2001 requires a 9 pin harness with 6 relays if you want to keep it factory western.
     
  11. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    So you have the 12 pin plug for sure??? It may be that someone upgraded it from the 9 pin but if that's true it's not a problem, it will work fine.

    I am beginning to wonder if you have the correct relay setup. You say you have six relays, that means you should have the HB3 / HB4 headlight system. Look closely at the glass on the front of the lamp lenses and verify this. It may have HB3 / HB4 with the five relay setup as shown on page 80. http://library.westernplows.com/ddcommon/dd_pdf/pdfs/22373.07_110108_for_web.pdf
    Clearly you have some sort of cross connection between the high and low beam through the relays. There is a common dark blue wire on page 86 that connects all four headlights together and then goes to the plow high beam positive wire. My guts is telling me that this has something to do with it. Without the plow being connected the relays are all in their default condition so they have nothing to do with the problem.
    Check also if you actually have an independent DRL bulb. If not then you need to be using the setup on page 80.
     
  12. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    Looking further at that six relay schematic I see that the original truck headlight power is simply redirected to either the truck bulbs or the plow. (Unlike the iso modules which redirect battery power) Both the high and the low beam relay pairs are switched together and all four will either be in truck (default) or all four magnetized to switch over to plow.

    With the plow disconnected all four relays are forwarding power from the original headlight plug wires to the truck bulbs through four relays and then to ground through the dark blue wires. Since the truck lights work fine without the harness then there must be a crossover between the plug and the relay, or from the relay to the truck bulbs. The other two relays shouldn't have anything to do with it. Whatever is wrong is wrong on both the driver's and passenger's side because the two sides are independent from each other.

    Since you have the six relay setup installed go to relay 1 and 2, disconnect the wires going to pin 30 on each of those two relays, this should make the passenger side truck lights go out. Then test the wires with a test light. These wires should be hot on one with low beams activated and on the other with high beam on. If they are both hot in high and low then the short / crossover is between the relays and the original truck plugs. If they are only hot on one or the other the problem is after the relay. The fact that the truck lights come on at all indicates that those four relays are operating correctly. You could do the same with the wires on pin 30 of relays 3 and 5 too but you will get the same result because the same problem exists on both sides.

    What I said above about the dark blue common wire going to plow headlight high beam was wrong, that dark blue actually plugs into a white wire, which goes through the grill plug and then on to the common ground wire on the headlights.... The schematic is ambiguous, it appears the white "line" wire goes to high beam but the picture of the bulb plug (actually says the white is common ground. (That's on page 73, 12 pin plow side) Seems this is just to make it difficult to troubleshoot.

    Sorry if this is complicated to digest. This 6 relay setup is very complicated and hard to follow at the best of times.
     
  13. Western1

    Western1 Senior Member
    from MI.
    Messages: 679

    Yea you can say this again!!!
    This 6 relay setup is very complicated and hard to follow at the best of times.
    Happy new year!