ok, got to working on my 85 stepsde to replace the hacked up/burnt wire harness. I already did a cab swap. so now getting it up to par for wiring.

I swapped in a complete 86 under hood harness and matching 86 dash harness along with the chassis sub harness for tail/brake lights also the 86 wiper motor.

**FYI 86 has plug change and wire routing change. weather proof plugs? NSS moved from chassis sub harness to firewall at engine sub harness connection.

this is a 40,000 mile harness from a 86 w150 there are no cuts/burns/splices on this 86 harness other than the washer motor wire/plug were melted. looks to have been on a manifold.

I have the stock dist by-passed/BR by-passed for full 12 volts to coil on stand alone IGN. system.

install and power it up. get every light/device to work except headlights and it starts with or with out the NSS.

park/turn sig/side marker/flasher/dash/dome/cargo/ashtray/glove box/intermit wiper-2 speeds.

swapped in another 86 dash harness and get NO POWER any where but HEADLIGHTS WORK-HIGH/LOW BEAMS WORK NOTHING ELSE WORKS OR POWERS UP.

SO I swapped matching dash harness back in and get every light/device to work but NO HEADLIGHTS!

not sure how to trouble shoot it other than swapping complete harness out.

I forgot the field wires on alt and fired engine up. they bounced around and sparked a couple time on the BATT stud of alt.

change field wire connectors and hooked them up. start/run engine and VR smoked for a no charge problem.

replaced VR and it charges fine now 14.5 volts.

with a test light I have 3 wires on headlight switch that is hot with switch off, 1 wire has a buzzer go off when probed with test light hooked to ground.

popped a fuse when I hit the spray washer motor = found the wires shorted together. cut out shorted wire and now it no longer pops a fuse and works the test light.

just came in after dark and confirmed the inst cluster lights work/dim with headlight switch = passed.


how do I get power out of switch to headlights?

can I toggle them on a separate switch?

and why does it crank/run WITH or WITHOUT NSS?

no power at headlight plug/bulb with switch on.

all fuse links seem to have power each side of connection, all fuses check good,

Is the hi-low switch on the turn signal stalk or on the floor? The NSS must be grounded some where in the wires from it to the starter relay.

hi low on dimmer switch at floor board.

I do have another NSS sub harness I can try.

can anyone walk me through trouble shooting this?

I have multimeter/test light and have no clue where or how to begin checking.

I am picking up a new switch just to rule that out today.

surely it cant be much, I have everything working and every bulb working, charging system working.

no headlights..

on a good note I did get the tail/brake light issues fixed. LOL!

With the headlight switch on you should have a hot wire at the floor switch connector. If you do then you have a bad dimmer. Sometimes they get corroded and end up working some times or not at all.

The headlight circuit is pretty basic. Power from the switch goes to the dimmer. and from the dimmer it goes either to the high beam or the low beam wires on the headlight, and from the light it goes to ground.

Pull the switch off the floor, with the light switch turned on, check for power to the center wire on the 3 wire plug. One of the other wires should also be powered. Manually click the dimmer switch, and the other wire should power up, and the one that was powered will loose the power. If you have power coming in, and none going out, the switch is defective. Can can also connect a jumper wire from the hot to either of the other plugs and get lights (be careful not to ground the wires). It is "normal" for the dimmer switch to fail by not making the connection through it.

If you have power through the switch, you need to check for power at the lights, on both high and low beam. I have seen total failure of both headlights, and bad grounds not allowing the lights to light up.

For you info, the replacement headlight switches are among the poorest quality new switches currently on the market! Do not assume a new switch is good, at all! We had to put 3 brand new out of the package headlight switches in my son's car before we got one where everything worked. Gene

I am over my head and running out of time. time.. with the wife having chemo treatments, me driving 100 miles a day for work, I need it fixed. I don't know how so I am dropping it of at a shop today to have it looked at/repaired.

I have to face the fact I have been beaten by my truck.

repair shop 77$ hr and hope they are fast about it.

Sorry to hear that! I'm betting on a bad dimmer switch. Gene

I agree with the bad dimmer and poor ground. Should be able to bypass the switch to prove it.

all done.

1) dimmer plug lead wrapped into harness but has a 2nd plug that was not connected in the main harness.

I don't see why I could not see it. wife said I was stressing over it too much. it should have been a snake and bit me a few times.

2) got a tail light wire backwards on the ebay chassis harness where they added a trailer plug.

3) 2 bulbs?

gave a newer SERVICE & CUSTOMS shop in town the work. had it done 2 hrs ready for pick up. 165$ they restore/repair older cars and trucks.

redid the rear of the chassis harness and wired my stepside tail lights up with factory plugs for bed removal, wired up the tag light.

they took the 2 stock tail light sub harnesses for a wide box, converted by cut/shorten/connected with stock plug connectors to my stepside mounted tail lights for easy bed removal and a tidy wire harness down frame/across back.

Worth every penny! Glad you got lined out. Your wife sounds like a smart lady!