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75 c10 electrical/fuse/wiring question - head lamps

  
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75 c10 electrical/fuse/wiring question - head lamps

 
tard01 tard01
New User | Posts: 1 | Joined: 10/12
Posted: 10/26/12
09:47 AM

hi guys, looking for verification/tip on troubleshooting 2 electrical problems i have.
1) head lights don't come on
2) back up lights dont come on


1) head lights don't come on - I can get the yellow lights to turn on via hazards or turn signals, so i know the wiring/bulb is good. I can also get the rear brake lights to turn on. But when fully engaged, the front lights (head lights and yellows) wont turn on.

Since i know the lever/switch to turn on the lights works (since rears turn on), i feel its ok.
since i know the yellows work via blinker/hazard, they seem ok.
I have not verified the actual bulbs themselves work on teh headlights.

Since the lever appears normal and hte individual lights come on for the yellows in other tests, i suspect a relay or fuse issue. Does this sound reasonable?

i visually inspected the fuses, i didnt see an obvious blow.

I found this fuse diagram, but didn't see which one specifically would be the one i need checked, but it did confirm that the turn signal and hazard circuits are seperate, which gives me hope the issue is a simple fuse problem.

http://www.chuckschevytruckpages.com/77fusebox.html

my best guess is that J is the head lights? though by the name, i'd suspect it was meant for the interior - not sure if panel refers to the front panel - doesn't seem to fit the name, but i dont see a better identifier for the front headlights.
J - Fuse - Panel Lights





2) back up lights dont come on - not sure if seperate issue, or maybe the bulbs are dead, but curious if anyone suspects it might share a circuit with the head lights, oddly? i'll verify its fuse location when i get sunlight tomorrow.




if at minimum someone can help me identify the name/slot of the headlights based on the labeling in the link i provided, that would help me quite a ***


side note - my continuity tester is scheduled to arrive today, but wanted to see if i couldnt identify the correct fuse prior.  

Tbeeks Tbeeks
New User | Posts: 13 | Joined: 09/12
Posted: 10/26/12
04:56 PM

working on the same problem man , my park lights come on on the first and second pull sw position , but when i pull the sw all the way out for the headlights the park lights go off headlights work fine.  

hotrodace hotrodace
User | Posts: 156 | Joined: 03/11
Posted: 10/26/12
07:04 PM

1) head lights don't come on - I can get the yellow lights to turn on via hazards or turn signals, so i know the wiring/bulb is good. I can also get the rear brake lights to turn on. But when fully engaged, the front lights (head lights and yellows) wont turn on.




Sounds like the headlight switch. The headlights and markers are fed through the switch. You should have 12vdc at the switch on the red 12 gauge wire. From there the switch feeds out to courtesy, instrument and headlights.
For the headlights you should have 12vdc out of switch (when pulled for headlights) on 16 gauge lt. blue.
This lt.blue goes to the dimmer switch. At the dimmer switch the 12vdc it toggeled either hi/low beams on 16 gauge tan or lt. green.
Brown at the headlight swith goes to the marker lamps.
If you have 12vdc on red at the switch and its pulled for headlights you should have 12vdc out on LBL and BRN.
Just a note:  Headlight switches also have a thermal cutout that could be a problem at some point.

If you dont have 12vdc at 12 gauge red on headlight switch you have wiring  problem between the headlight and ignition switches.  

waynep71222 waynep71222
User | Posts: 106 | Joined: 04/12
Posted: 10/26/12
07:13 PM

perhaps this will help..

Sw144headlightswitch 1  

waynep71222 waynep71222
User | Posts: 106 | Joined: 04/12
Posted: 10/27/12
07:36 AM

tard01
TWO  electrical problems


1) head lights don't come on
1A  as you see above.. the red wire supplies power to the headlight circuit...  there are multiple circuits inside the ignition switch...  there is an internal circuit breaker just for the headlights inside the headlights switch...   do you have power to the red wire...   when you pull the headlight switch out to the headlights position.. do you have power on that what is probably a yellow wire???? it hooks to the center terminal of the dimmer switch on the floor..

the dimmer switch is an ON-ON switch...  when you depress the button .. you will send power from the center terminal to one of the outer terminals. push the dimmer button again.. sends power to the other terminal.. on a 75... one wire should be light green. . the other should be tan...


2) back up lights dont come on

that circuit is powered by the ignition switch... and controlled by the neutral safety switch on the top of the column almost to the firewall on automatic versions..

update..

the back up light wire is fed from the IGN 1 wire on the switch to various places and the back up light fuse... where the wire from the fuse block is dark green.. goes over to the back up light switch...

from the back up light switch the wire is light green and goes into the tail light harness...  

waynep71222 waynep71222
User | Posts: 106 | Joined: 04/12
Posted: 10/27/12
07:42 AM

Icon QuoteTbeeks:
working on the same problem man , my park lights come on on the first and second pull sw position , but when i pull the sw all the way out for the headlights the park lights go off headlights work fine.

with some years ..   the front parking lights DO TURN OFF when the headlights come on...

these are usually earlier years...

do the tail lights come on and stay on in both positions.. if so.. that would be normal