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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: 82apache on December 23, 2019, 09:42:45 PM
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82 K20 Left of the brake booster and through the firewall, 2 wires 1 green and 1 pale yellow or white, stuck together like speaker wire. In the cab they appear to run up behind the instrument cluster, in the engine bay the other end dives into the plastic wire loom down by the frame that also houses the Rear Intermediate harness.
I don't have them on my '79 nor my '86. Any clue as to what they are?
And Merry Christmas!
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Post a pic, please.
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Maybe the backup light and turn/hazard signal bulb.
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This morning a buddy of mine said it might be for the reverse switch. --700r4
Does that ring a bell?
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No.
Sounds like something someone added, trailer brake etc. but
Post a pic, please.
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This is not a pic of mine but it appears to show the same wire combo. The routing seems to be different as well but mine has been molested so that might account for that. I am looking at a wire combo that has something to do with the fuel tanks?
The yellow-green combo roughly center of the pic
http://67-72chevytrucks.com/vboard/attachment.php?attachmentid=136170&stc=1&d=1113932884 (http://67-72chevytrucks.com/vboard/attachment.php?attachmentid=136170&stc=1&d=1113932884)
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No.
Sounds like something someone added, trailer brake etc. but
Post a pic, please.
I considered that however the plug/grommet thing where it comes through the firewall appears to be factory and there is no evidence that a brake controller was ever mounted to the dash.
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Flux Capacitor? 8)
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Flux Capacitor? 8)
Hmm I don't think so but with an old truck it is always hard to tell what all a PO has been doing with the wires. lol
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Do you have dual fuel tanks? That may be the harness for the sending unit.
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Do you have dual fuel tanks? That may be the harness for the sending unit.
I do have duel tanks.
Holidays have kept me busy so I have not had a chance to climb under and trace them but I am leaning toward that being it and for some odd reason having been rerouted by the PO into the rear intermediate harness loom. (any idea where they are supposed to run?)
The deeper in I get the more I think the wiring work was done by someone who almost, but not quite, knew what they were doing. lol Local 2 bay shop with a crusty old Cooter type that knew how to make it work but was not very interested in actually doing it correctly, perhaps.
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Dual fuel tanks have a rubber plug and wires running through the firewall above the brake pedal area, but there should be at least 4 wires. At least two of them should be tan or tan/white because that is the typical color of the sending unit wire.
Bruce
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(https://uploads.tapatalk-cdn.com/20200104/66b06813ff4f900dbf78c6aeba1dc627.jpg)
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(https://uploads.tapatalk-cdn.com/20200104/66b06813ff4f900dbf78c6aeba1dc627.jpg)
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Thanks but these wires are not actually part of the RIH, nor the Rear harness, they are just routed through the same wire loom tubing as the RIH.
The PO had spliced into the the RIH to power some sort of a power receptacle in the interior bed wall and in the process cut off both the plug at the end of the RIH and the plug at the beginning of the rear harness. The RIH and the RH are currently spliced together instead of plugged together and that is what got me started on this. I am replacing both harnesses and found the extra wires in the loom tube.
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Dual fuel tanks have a rubber plug and wires running through the firewall above the brake pedal area, but there should be at least 4 wires. At least two of them should be tan or tan/white because that is the typical color of the sending unit wire.
Bruce
OK, Looking from the grill, these come trough the firewall through a rubber plug located to the left of the brake booster and through the right side of the engine indent. Only two wires and those fused together like speaker wire is. It all looks factory and it does not appear that there was ever any other wires breaching the firewall through that plug.
The weather will be too wet to crawl under for the next few days, I will see if I can get a good pic tomorrow.
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OK lets try this
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Those siamesed wires appear more like light blue and light green in that image. They are in the torque converter clutch circuit of an MV4 (TH350C) or MD8 (700R4) transmission. Is there a free-hanging orange connector with one light green wire in the vicinity of the fuse box?
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Those siamesed wires appear more like light blue and light green in that image. They are in the torque converter clutch circuit of an MV4 (TH350C) or MD8 (700R4) transmission. Is there a free-hanging orange connector with one light green wire in the vicinity of the fuse box?
I am not seeing one.
Still a swamp under the truck but I twisted myself into a pretzel and tried to trace them under the dash. Where they are not faded they seem to be green and light green. The come through the firewall up behind right side the gauge cluster then seem to head off toward the passenger side I lost them at that point. Could they be for the tank switch?
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Yep! Dark green/light green pair; looks like it connects the dash switch to the fuel tank selector valve mounted under the cab.
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Next time post a pic to begin with. Could have saved a lot of time playing guessing games.
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Yep! Dark green/light green pair; looks like it connects the dash switch to the fuel tank selector valve mounted under the cab.
Thanks! Any idea what the original routing was?