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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: beastmode86 on October 01, 2013, 11:01:21 am

Title: Headlights still won't work
Post by: beastmode86 on October 01, 2013, 11:01:21 am

 I have a 86 c10 silverado that has hacked up wiring. The factor wire loom for the head lights are still intact. I re-wired the starter and the alternator using all new wire and fusible links. I put a new headlight switch in and still nothing. My fog lights and my tail light work, but no headlights. I have all the wiring diagrams but i'm still can't locate the problem. Any advice would be greatly appreciated.

Title: Re: Headlights still won't work
Post by: 81_Chevy on October 01, 2013, 11:30:57 am

is there a ground to the headlights?

Title: Re: Headlights still won't work
Post by: Boone83K10 on October 01, 2013, 01:30:58 pm

yes, first thing is to the check the grounds on both sides. make sure they are clean with bare metal.

next, check your dimmer switch which is on the floor. It has 3 wires going to it, Yellow, Light Green and Tan. Yellow which comes from the headlight switch. Lt Green which is the feed for HIGH beams and Tan which is for LOW beams.

I bet you have a bad dimmer switch.

Title: Re: Headlights still won't work
Post by: beastmode86 on October 01, 2013, 04:07:25 pm

Thanks for the reply's. I'll check the grounds when I get home from work Boone83k10. 81_chevy I don't have a floor dimer switch.

Title: Re: Headlights still won't work
Post by: bd on October 01, 2013, 08:45:01 pm

Quote from: beastmode86 on October 01, 2013, 11:01:21 am

I have a 86 c10 silverado that has hacked up wiring. The factory wire loom for the head lights are still intact. I re-wired the starter and the alternator using all new wire and fusible links. I put a new headlight switch in and still nothing. My fog lights and my tail light work, but no headlights. I have all the wiring diagrams but I still can't locate the problem. Any advice would be greatly appreciated.

Perhaps this will help.  Do you have battery power on the red wire (Ckt 2) feeding the headlamp switch?

• No - You've lost headlamp feed to the headlamp switch.  Recheck the fusible links and connections at the firewall junction block and starter.  If okay, check power through the bulkhead connector on Ckt 2.
• Yes - With the headlamps switched ON, do you have power on the yellow wire (Ckt 10) at the headlamp switch?
  
  
• No - You've lost headlamp power at or through the headlamp switch.  Service the red and yellow wire connections to the headlamp switch.  If the connections are sound, replace the headlamp switch.
• Yes - With the headlamps switched ON, do you have power at either the light green (Ckt 11 - high beam) or tan (Ckt 12 - low beam) wires at the dimmer switch mounted to the left side of the steering column under the dash?
  
  
• No - You've lost headlamp power from the headlamp switch to or through the dimmer switch.  With the headlamps switched ON, verify power into the dimmer switch on the yellow wire (Ckt 10).  Service the wire connections to the dimmer switch or replace and adjust the dimmer switch as needed.
• Yes - Check power on Ckt 11 or Ckt 12 (whichever was hot at the dimmer switch, previously) through the bulkhead plug and on out to the headlamps.  If you have power to the headlamps, service the wire connections to the headlamps (WD-40 works wonders), repair the open headlamp ground(s), and/or replace the lamp capsules as needed.

Title: Re: Headlights still won't work
Post by: beastmode86 on October 01, 2013, 09:11:15 pm

The truck still starts, but no dash lights work except my left turn signal light. Just more info. So I checked the headlight grounds at the headlight and they are good. I ran my own wire to the choke with a in-line fuse and its not getting power now(it's wired to the Ignition side of the fuse box). I checked the ignition fuse and its getting power but where my choke wire and two sprate orange wires go into the fuse box they are not getting power. My fusible links are still good. I'm not getting any power to my headlight switch either. I don't know what Clt.2 means or where to located db. Where are the grounds under the dash that I might check.

Title: Re: Headlights still won't work
Post by: bd on October 02, 2013, 01:28:23 am

Approach one symptom at a time, systematically, and DON'T make any assumptions!  Avoid skipping over troubleshooting steps. 

The best place to begin electrical diagnoses is verifying that battery-to-engine, battery-to-frame, engine-to-frame, and engine-to-cab grounds are present and in perfect condition.  You could spend days chasing power delivery problems only to discover the issue was a simple ground problem.  Better to avoid the aggravation.

Quote from: beastmode86 on October 01, 2013, 09:11:15 pm

...no dash lights work except my left turn signal light...  I'm not getting any power to my headlight switch either.  I don't know what Ckt.2 means or where it's located db....

'Ckt 2' refers to the wire number on the factory wiring diagram (circuit #2).  Refer to the factory 1986 Wiring Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Wiring/ST_352_86_1986_Chevrolet_GMC_Light_Truc_Wiring_Manual_CK_10_30_Only.pdf) in our Technical Pages (http://forum.73-87chevytrucks.com/smforum/index.php/board,5.0.html).  The manual takes some time to open, so be patient.  Save it to your PC's hard drive for faster access in the future as a "pdf" document.  Since you stated there is no power to the headlamp switch, study the factory wiring diagram and physically trace Ckt 2 from the starter, to the firewall junction block, through the bulkhead connector, to the headlamp switch.  Circuit 2 is battery feed to the headlamps.

Quote from: beastmode86 on October 01, 2013, 11:01:21 am

...My fog lights and my tail light work....

The caveat: because you posted that the taillights work, unless the taillights have been altered to operate off of a switch that is separate from the headlamp switch, you must be getting power to the headlamp switch via the orange wire from the fuse block.  It's inevitable.  The heavy gauge red wire is headlamp feed; the orange wire is taillight/dash light feed - both feeds come into the switch, but for different purposes.

Quote from: beastmode86 on October 01, 2013, 09:11:15 pm

...no dash lights work except my left turn signal light...

Refer to Diagnosing dash lights that don't work (http://forum.73-87chevytrucks.com/smforum/index.php/topic,26558.msg221363.html#msg221363) for a troubleshooting procedure on the instrument cluster lamps.  Don't overlook the possibility of bulbs simply being burned out.

Quote from: beastmode86 on October 01, 2013, 09:11:15 pm

...Where are the grounds under the dash that I might check?

The instrument cluster (dash) ground uses a black wire that runs between the harness plug at the back of the instrument cluster and the cab sheetmetal adjacent to the park brake pedal assembly.  Make sure the sheetmetal connection is totally clean and tight.  It's common for oxidation and dust to degrade electrical connections between the harness plug and the copper foil of the circuit board that's attached to the back of the cluster.  You can clean the foil using a pencil eraser or crocus cloth, but be careful that you don't peel the foil loose from the plastic substrate.  Connection issues also develop between the bulb sockets and the circuit board.  Yet, sometimes the solution is as simple as reseating the harness plug into the back of the cluster housing.

Title: Re: Headlights still won't work
Post by: rich weyand on October 02, 2013, 01:47:13 am

Also, sometimes the instrument panel bulb holders lose contact with the circuit board.  I had some that lit up as soon as I took them out and put them back in.

Title: Re: Headlights still won't work
Post by: beastmode86 on October 02, 2013, 10:14:34 pm

I found a ground block up by the parking break. Cleaned all 4, 3 clip style and one ring terminal. I ran all new ground wire in the engine bay per previous remarks. Still no lights. I have no power to the lightswitch or the dimer feed wires going into the column. Does that mean the dimer switch is bad?Still a few things to check. I still don't know how to locate the ckt 2 and 10.

Title: Re: Headlights still won't work
Post by: bd on October 03, 2013, 12:51:41 am

At this point, too much emphasis has been placed on circuit numbers. The only reason I mentioned them was to help you tie your vehicle wiring to the factory wiring diagram and make the diagram easier to follow. 

You should regularly refer to the factory wiring diagram, previously linked, for all subsequent discussion.

To clear up any confusion regarding circuit numbers thus far:

• Circuit 2 is the 12-gauge red wire that runs from the starter up into the cab to feed battery power to the headlamp switch and the tail light fuse in the fuse block.  That's all it does.
  
  
• Circuit 10 is the 16-gauge yellow wire that supplies power from the headlamp switch to the dimmer switch.
  
  
• Circuit 11 is the 16-gauge light green wire that connects the dimmer switch to both high beams.
  
  
• Circuit 12 is the 18-gauge tan wire that connects the dimmer switch to both low beams.

----------------------------

As mentioned, circuit 2 is the 12-gauge red wire running from the 3/8" stud on the starter solenoid up to the firewall junction block; it then runs through a short 16-gauge fuse link and on to the firewall bulkhead plug.  Circuit 2 continues through the bulkhead plug into the cab where it splits into two leads with one lead feeding battery power to the fuse block and one lead feeding battery power to the headlamp switch.  The red wire will be taped into a harness all the way from the starter to the bulkhead plug, peeking out only briefly at the firewall junction block.  It will also be taped into a wire bundle under the dash. 

If all the wires at the headlamp switch are dead, probe the stud on the firewall junction block.  If you find power there, your wiring problem is in the 12-gauge red wire (or its fusible link), between the firewall junction block and the splice under the dash where the 12-gauge red wire splits into two.  If there is no power at the firewall junction block, the issue is in the 12-gauge red wire between the junction block and the starter.  I think your trouble is in the 12-gauge red wire somewhere between the starter and the headlamp switch.  You just need to narrow it down.

Title: Re: Headlights still won't work
Post by: beastmode86 on October 03, 2013, 07:10:51 am

 I have 12.5 Volts at the junction box. I must have a problem between the fire wall and the fuse box. I guess I need to see whats going on behind the fuse box. Thanks for the replies. On a happy note, the new ground wires made the truck run so much better.

Title: Re: Headlights still won't work
Post by: beastmode86 on October 05, 2013, 12:04:13 am

 Wow, what a turn of events. So... I took the fuse box face off and found the two pink wires bd referred to in a previous remark. Still no power. I check the continuity of the ground again, it was good (the ground by the parking break). I also use the same ground with my volt meter to check other hot sources to kill two birds with one stone(again checking the ground). Long story short who ever had this truck before me must not of been using the alternator ???. When I re-wired the engine bay I used the wire leads they had tied into going into the back of the fuse box fire wall side (the original wire loom is gone)They had the fuse box main wire (ckt 2) running it to the alternator and the ignition wire coming from the fire wall going to the distribution block. I ran both red 12 gauge wires coming from the fire wall to the distribution block and I got power to the headlight switch, but still no lights. I followed the above steps and changed the dimmer switch and my head lights finally work!! Thanks for all the replies and helping me out. Whew, now on to the step to getting her on the road.

Title: Re: Headlights still won't work
Post by: bd on October 05, 2013, 09:26:49 am

Congratulations for a job well done!!  8)

Title: Re: Headlights still won't work
Post by: bake74 on October 06, 2013, 10:54:35 am

       ;D ;D ;D 8)  I don't care what type of personality you have, when you get done fixing a problem like that you can not help but to feel proud and happy about yourself all rolled up into 1.