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Two electrical issues

Discussion in 'Chevy Trucks' started by Woodland, Nov 21, 2008.

  1. Woodland

    Woodland Senior Member
    Messages: 269

    First a little background info. The truck is a 2004 Chevrolet K2500HD with the factory tow package. I purchased it used this spring.

    Issue #1 - No power at the battery feed line on the trailer hitch. I have been using a dump trailer all summer, using the hydraulics probably 2 or 3 times per week. All was well until about a month and a half ago when the dump action slowed to a crawl. Upon investigation, I was somewhat surprised to discover a drained battery. I tested the battery feed at the trailer hitch and discovered there was no power. thus the battery was not being charged. I have since charged the battery and continue to use the dump without issue. I was very surprised to learn that I could dump the bed so many times on a single battery charge. Having been through all of that, I am unsure of when the lack of power to the trailer hitch began. So, my question here is, where do I begin to look for trouble??

    The trailer hitch and all of the wires leading into it look to be in very good condition. I checked both fuse blocks (in cab and under hood) and was not able to find a fuse labeled for that particular wire (I did find one for the trailer backup lights and I checked several other fuses but none were blown). Is there another fuse or relay located somewhere else that I am not aware of? Any thoughts on other possible causes? I do dread the idea of having to trace the entire wire looking for a short.

    Issue #2 - I am installing 2 55watt task lights to the trucks bed rack through a relay. I want them to use the same switch that the factory installed cargo lights use. I.e. when you press the factory button installed on the dash, both the cargo lights beside the third brake light & my installed lights come on. Has anyone done this before that might offer some advice on how best to locate the wire that leads to that switch?
  2. tattooedplower

    tattooedplower Member
    Messages: 31

    On my truck the battery feed line was not hooked up under the hood. I checked to see what color it was at the hitch and started tracing it back to the engine compartment. I found it folded over and electric taped a million times right around the area of the master cylinder. It already had a lug on the end of mine. I hooked it right to the fuse block in the engine compartment on one of the aux power studs that has a large 30 amp fuse. Hope this helps. Hunt for a while mine was hidden well.
  3. lilweeds

    lilweeds PlowSite.com Addict
    Messages: 1,178

    You need to put the 40 amp fuse on stud 2 if I remember correctly. Not sure on your second problem.
  4. the ******* thing didn't like my first post heres version 2, pull plug off back of switch turn key on, find powered wire, with a test light or multimeter. do not probe insulation of wire either probe plug spade or back of plug where the wire enters. the other wire is the one we are interested in. this is going the be signal wire for your relay. most auto relays pull 1 amp or so it will not hurt your circuit. find a spare12 v power source capable of supplying 15 amps or so(see below) either a spare in your fuse box or pull from under the hood but be sure to fuse it. the following is for a bosch style relay very common any stereo shop radio shack etc should carry terminal 85 and 86 are coil terminals. ground one attach other to above mentioned wire at switch. power terminal 30 with above mentiond fused power source, fuse for X amps per light (55w/12v equals approx 5 amps 80/12v watt 6 and a bit etc) add a bit to the draw ie 5 amp draw allow for 7. 6-8 amp draw a ten etc. use at least 16 gauge more then two lights or paticular long run use 14 gauge the heavier wire is worth the little bit extra money it will hold up to corrosion kinking breaking much better etc. connect term 87 to your lights. you may want to add a swith between your splice in dash and the realy so you can turn on the cargo light and leave the large ones off. 87a will not be used however it will be hot when the lights are off so be sure it cannot contact any metal, perhaps break it off tape it, both etc. Other relays can be used just be sure there capacity matches your needs wiring will be similar.
  5. RichG53

    RichG53 PlowSite.com Addict
    Messages: 1,135

    BOY that was long and very confusing ...A drawing would help. !!!!!!!!
  6. Woodland

    Woodland Senior Member
    Messages: 269

    I think this is what I was looking for, somewhat. I don't have any problems with the actual wiring. My questions was in regards to locating the wire used by GM to run the cargo lamp switch on the dash. You seem to be suggesting that I will do best to pull the front dash cover off to access the switch? or can I access it from under the dash somewhere?

    Excellent idea. I had not even considered this as a possibility...until now. Thanks
  7. Riccas

    Riccas Member
    Messages: 60

    The 3rd brake light cargo light is positive ground so keep that in mind when wiring before you cause a bad wiring problem.

    As for the trailer wiring i thought you said the battery wasn't charging... so why are you looking for problems at the trailer plug (unless you meant there is a battery on the trailer and did no specify)

    To get the trailer wiring to work make sure Stud B fuse is installed and fine, it should be a 40/50 amp fuse located next to stud A. These are typically not installed you must do it yourself when installing the trailer brake harness. There is a junction under the bed where the trailer wiring connects into. Disconnet that and re-connect after cleaning. There is 1 more spot to check up by the fuel tank where an additional wiring harness is for 5th wheel. Check to see if you are getting power there, if not the problem is pre-bed. If you are, then its post cab and probably the connection under the bed.

    PM me if you need further assistance.
    -- Rick
  8. Woodland

    Woodland Senior Member
    Messages: 269

    Could you elaborate please, I'm not sure just what you mean. Would this have any effect if my only contact with the factory switch was to tap into the hot wire back to my relay as the "switch" trigger?

    Yes, there is a battery on the dump trailer that runs the hydraulics for the dump action.

    I will look into this later this week. It's way to cold to crawl around the truck this weekend and I can't get to the garage until late next week, but I'll let you know how it goes.
  9. sorry for the longwinded explanation. I am on dial up so drawings and diagrams kill me. I am not familiar with the newer chevs however in my experience with vehicle wiring the area near the back of a switch or accessory is "usually" the the best place to get access to a wire as it is usally the least crowded and less chance of disturbing other harness\wires. and they are easy to identify so you do not make a wrong cut.. I do not have diagrams for your truck but (i dont mean to start a argument here) i believe riccas is wrong about the cargo light being a positive ground as no vehicle made in north america in the last 50 years is positive ground about the only people that use that are old brit vehicles (triumph leyland) and i believe very old some very old transport trucks, macks maybe? If riccas meant that the light is hot and the switch provides a ground path that could be entierly correct if that is the case he seems to be in a better position to help you then me as you definetly will want a wiring diagram as backfeeding grounds can do funny things especially if through a digital control module.