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85 K5 Dual Headlight Wiring

Desert_K5

Desert_K5

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I'll be up front about electrical..... I suck at it. My 85 has the factory harness and had 4 spot lights put in place of the hi/lo bulbs. I can find the wiring diagrams for the LMC upgrade and the single light setup, but not the dual stacked lights on my 85. The harness is in good shape, except the factory plugs have been cut off.

Can someone point me to a wiring diagram, preferably in color. Wiring for dummies style?
 
Desert_K5 said:
I'll be up front about electrical..... I suck at it. My 85 has the factory harness and had 4 spot lights put in place of the hi/lo bulbs. I can find the wiring diagrams for the LMC upgrade and the single light setup, but not the dual stacked lights on my 85. The harness is in good shape, except the factory plugs have been cut off.

Can someone point me to a wiring diagram, preferably in color. Wiring for dummies style?
Click to expand...

Dang, looks like ALL the links to headlight relay wiring mod wiring diagrams are dead.

Lights are relatively simple. One pin on the headlight is ground, one will be high, one low if a high/low bulb, can't remember if the two pin bulbs are low or high only.

IMO since you are starting with cut off plugs, time to "upgrade" to relays. Wiring diagrams for the various years (stock) are at the link in my signature. And if going with the relay mod, I'd run all four beams the same...4 low beams, 4 high beams. These bulbs suck at lighting, more is better IMO. Relay mod is pretty easy, good way to cut y our teeth on wiring. It's not that hard and invaluable knowledge if you keep messing with vehicles.
 
Thanks for the links! I went ahead and ordered the harness from LMC to do the relay style setup you've mentioned. I appreciate the help for sure. When it gets here I'll get it spread out on the bench and go from there. Thanks again.
 
RootBreaker, thanks for the offer. I went ahead and ordered the relay setup over the weekend. If you would like to still do the pictures that would be helpful until the relay harness gets here. I appreciate the help!
 
so few years ago i went to rewire my entire truck with a ez-wiring 21 kit. I LOVE THIS KIT.. and would do it again in a heartbeat. I did not do the relay mod but the new wires were thicker and my lights are brighter. It is also a standard GM fuse block which was cool. Originally you drill a 1" hole and run the wires but I crimped all wires back through the OEM harness. ONLY thing I did wrong and would redo is I bought the ALL BLACK model. it says oil sender every 12" on wire but duhhh manuals state a color!!!!hah...

I did salvage my under hood harness...
 
so the high beams... so looking from drivers perspective at the plug.. black on left and green on right..

20160524_174508.jpg


then low beams has more wires...
Green bottom, black left and whatever color on right...

20160524_174410.jpg
 
Thank you. That will help, I appreciate it
 
Just to throw a wrench in the spokes ...... The headlight wire position, is different between the 5x7 lights, and the 3x5 lights. I found this out when switching my '81 c-10 2 square light front end over to the 4 square light frontend. Had to re pin the connectors to make both beams work correctly!
 
The harness showed up & I'll update when installed.
 
Ok here we go. I hooked up the harness to the lights, relays and grounds as labeled. Where I'm stuck at is the plug that says existing harness. I found two wires with power and a ground from the harness on the passenger side and when I turn on the lights only the high beams come on. Could the headlight dimmer switch be bad or am I hooked up incorrectly to feed the LMC harness properly? It looks like I just need to feed the LMC harness with power and ground and the relays do the rest?
 
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Both relays are getting power and replaced the headlight dimmer switch on the column. Triple checked wiring hookup, swapped headlight plug positions to verify all 4 lights work. High beams work then switch to low beams and no lights. Any suggestions???
 
Anyone have any ideas that could help?
 
Desert_K5 said:
Anyone have any ideas that could help?
Click to expand...

Only thing I see that you didn't mention is the headlight switch itself. I'm running on fumes here, which headlight is the low? The 3 pin? If that's the case, then the switch powers only one pin on that light (a single wire from the switch, then branched off further down to the other light), while on high it's powering the other non-ground pin, which is split to all four lights.

Are you getting 12V on the low beam wire when in that position and hooked up to nothing? IIRC, when you pull the dimmer lever back to switch, if you hold it back, it powers both the high and low circuit at the same time. No idea how that might help, but just thought of that as well.
 
There are no plugs on the stock wiring harness (previous owner cut them off) I'm using the attached as a guide..
light green = high beam
tan = low beam

The tan wire gets power (11.8) when low beam is on and clicks the relay. When switching to high beam the tan wire has zero volts reading.
I'm lost on why it gets to the relay but no low beams unless the LMC harness / relay is pinned wrong?

80hlightschematic copy.jpg
 
That's a single headlight diagram, we're going for four, right? Three pins are high/low beam. Two pins are high only.

Use the voltmeter as a guide, forget any schematic that says "typical". Generally they are ok, generally doesn't work when you are dealing with an electrical problem. That's why GM didn't put out service and electrical manuals covering "model years 1981-1987". :) Sorry, "typical" screams Haynes, and while they may be ok sometimes, they are not when you are knee deep in wiring. Rant over. The only thing you care about is making sure you are working with headlight wiring only (not marker/turn signal) and that you know which wire is high beam and which is low coming off the switch.

Low and high aren't on at the same time...when switched to high beam tan should NOT have voltage, since it's low. The headlights should only be getting power to the proper pin when the headlight dimmer is in the proper position...using that schematic to demonstrate, 12V to tan when in low, 12V to lt green when on high.

All your relays are doing is taking the load off the headlight switch (along with perhaps increasing load capacity of the wiring to the headlights). 12V from battery to the relay, should be 12V out to the headlight when that relay closes. Wire color is irrelevant when modifying factory wiring, the position of the wire on the relay is.

You using a relay somewhat like this?
Driving_light_relay_wiring_diagram.png


In your case, again using the "typical" diagram, assuming low beam setting. 86 would be the tan wire as it comes off the headlight switch. 30 probably comes from the battery. 87 goes to the low pin on the headlight. 85 obviously just goes to ground. The GM oval relays if used, have five terminals, but same basic idea. I'm *assuming* the layout of relays is some sort of standard.
 
I appreciate the help dyeager. Yes it's a four headlight setup. Just using that diagram for the two wires coming out of the harness I needed (high/low)

I'm using the LMC heavy duty harness and snapped a couple crappy photos. The tan wire is acting properly which is what has me screwed up. The LMC harness appears to just need the tan and green power wires to the relays ( and grounds ).
Tan and green seem to be working properly.

IMAG3007.jpg

IMAG3008.jpg
 
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