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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: 74bluebowtie on April 23, 2014, 07:51:57 AM
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Little introduction on my 74's issues: I don't use it much in the winter, mostly just hauling firewood, project materials, mulch etc.- truck stuff.
Some rather large wood rats moved into it the winter before last, the type that required small "have a heart" traps to catch. My dog was trying to catch one of them and snatched a hold of the driver side tail light wiring ripping it out - this where my repair begins.
So I attempted to determine which of the wires were the brown & black - the colors aren't that distinguishable on a 40yo wiring harness, the yellow and light green are easy enough. Thought I had it all figured out and was testing turn signals and the DS marker light was illuminating when the directional signal was on PS - figured I crossed something.
Started checking each of the four main wires at the rear plug to ground, everything checked out from the plug to the lights, but I had a ground on the harness to the to the front - checked the whole length and found a another badly chewed area corrected that, still had the ground.
Disconnected the plug at the firewall( with bulbs removed) and the harness to the rear is clear of grounds but the plug through the firewall is grounded on both turn signals and brake signals. I disconnected the harness at the base of the steering column and the turn signal ground cleared, I pulled the steering wheel checked both end of the harness and did find one blue wire cut, re-taped it but the ground is still there when plugged back in.
Disconnected both the brake switch and the light switch to attempt to eliminate them but my ground is still there.
Nothing looked chaffed from the firewall through the bundle behind the dash but all the fuses blew at some point. I need to run and get some fuses but with these grounds I'm pretty sure they will just blow.
Sorry for the long winded first post - just wondering if anyone has had a ground back through the firewall and where to look.
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I think my ground on the turn signals is the indicator bulbs in the dash - had a bit of a brain fart on that one.
Still doesn't make sense on the brake switch lines
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On my 74, had some what the same issue. I ended up rewiring a good section for the rear. The PO did a good job of crossing and switching wires. I got frustrated and just rewired it all from the junction block on the firewall back.
So here in the tech section you can find the wiring diagrams (http://forum.73-87chevytrucks.com/smforum/index.php?topic=11766.msg87585#msg87585) for our trucks.
I have a step side so I used the step side wiring diagram, do not know if yours is fleet side or not. But regardless, if you look through the wiring diagram it is pretty easy to wire them up. Make sure of a few things.
1: your ground strap from the inner fender area to frame is there and it is good.
2: your light sockets might need to be cleaned and or replaced if you still have problems, they corrode from being so old.
I would also suggest you get some reset-able fuses so you do not keep blowing fuses like this one.
(http://i1302.photobucket.com/albums/ag134/bake7466/random%20pics/fuse2_zps7eda5c97.jpg)
(http://i1302.photobucket.com/albums/ag134/bake7466/random%20pics/fuse_zps629a02f2.jpg)
They come in different amp ranges. I use them all the time.
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I figured the problem out. Apparently when I had the column apart I pulled the hazard switch - from the prints I have the brake and signal lights are engaged in the circuit thus the bulbs in the dash were the source of the ground.
Feel kinda stupid screwing around with a job all day that should have taken less than an hour. Everything works now, except the horn, as I broken the green button off again, glued it last time. I'll get a new one someday.
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Glad you got it working again.