Headlight problem

[Yukon Jack]

A buddy is having a problem getting his headlights to work. If he just pulls the light switch halfway out, to the parklight position, the parklights come on and the blinkers all work. If he pulls the light switch all the way out, no park lights and no headlights but he does have tail lights. Bottom line, everything works except the park lights and headlights with the switch fully on. Tony got his tester out and it doesn't appear that he is getting juice to the headlights but it doesn't make sense why the park lights work with the switch half way out but not with it all the way out. There's one wire plug that comes out of the harness and goes through the front radiator support that connects to the headlight assembly. He has no juice to it as far as he can tell. The park lights feed from a different wire, from a different wire harness. He is baffled as he has put in three different light switches in the truck and they all act the same, no headlights or park lights with the switch in the full out position.

Any thoughts?

[oteixeira]

Has this ever worked for him? If not, trace all the wires completely to make sure they are all there and not messed with. Also check for any cracks or burn marks in the wirring, at 30+ years old, these things lose insulation and arc out in the wierdest ways sometimes.

Orlando

[Yukon Jack]

He is just getting the truck running, so no prior knowledge on when they last worked.

[LeRoy]

Have you checked out the dimmer switch. This always seems to be the culprit

[tom hand]

Yep...what LeRoy said

[Yukon Jack]

Are you both referring to the dimmer switch that dims the dash lights or the high/low switch that changes the headlights from high/low beam?

[cdowns]

footoperated dimmer

[8.1PWR]

My 70 Chev did the same thing. I replaced the headlight switch.
Works fine now.

[LeRoy]

Ya, foot operated. Take a jumper wire and put it in the top prong slot and then into one of the lower two. One is high and other is low beam. Doesn't matter which. Just a quick check to see if that's the problem. This just happened to me and I checked everything except that switch. Damn rookie mistake on my part. lol

[God]

What year is the truck? It might be a year that did have parking lights with headlights... My 67 Chevys park lights go out when my head light come on......

[krue]

My vote is for the dimmer switch.

BTW welcome to the board to 8.1pwr.

[Longhorn Man]

If I read this properly, the parking lights work fine, but when the headlamps are turned on, the parking lights go out. (Do the tail lights stay on?)
in 67 the front markers turne off, that is the way they are designed.
If it is a 68 or newer, or a 67 and the tail lights also go out...then there is somethign askew.

[68c10owner]

i just had the same problem with my 68. someone here pointed me in the right direction and it was the foot dimmer. the plug was melted on the headlight wire and burned the terminal. i cut the wires, used 3 female connecters, cleaned all the dimmer switch terminals and now my lights work. it`s probably only a matter of time before it does it again but i`m planning on rewireing the whole truck soon and it`s just my project truck anyway so it doesn`t get much use right now.

[Yukon Jack]

As usual, my truck buddies come through! Dimmer switch on the floor was bad. This was on a 65 and neither of us had any idea that on 67 and older vehicles the parking lights on the front went out when the headlights are on.

Andy, Tony was getting no headlights or front parking lights when the switch was fully on, parking lights did work in the half way position. I believe his rear parking lights stayed on when he had switch fully on.

Tony's got it all straightened out now.

Thanks guys!

Tony wants to wire the truck so the parking lights stay on when the headlights are on. We assume he should just tap into the rear parking light wiring harness as those are on whether the headlights are on or not. Sound good to you all?

[71GMC_3/4T]

I had a 60 Chevy that worked the same way.
It's been so long ago, but I think I put a newer switch in ('cause there weren't any old ones around). I can't remember, but I may have had to splice in a newer plug to get it to work.
In any case, when I was done, the park lights stayed on in front when the headlights were on, much to my surprise.

[mrein3]

Now that your buddy has it all working do the conversion to relay operated headlights.

I just completed this project on my truck. I was amazed at how small the wires are that run to/from the headlight switch, dimmer, and headlights. What a joke!

The beauty about this conversion is my switch, dimmer, and wiring should last forever because there aren't that many amps flowing through them any more.

Not to mention my headlights are now a whole lot brighter.

Before the conversion I had 10.8 volts at the headlight with the engine off. After I had 11.8. I didn't bother to take readings with the engine on.

My eyes tell me the headlights are WAY brighter.

[Yukon Jack]

What is the conversion to relay operated headlights?

[mrein3]

Originally posted by Yukon Jack
What is the conversion to relay operated headlights?

Instead of having your wires go to the headlights you make them go to a relay. You need two relays. One for high beams and one for low. The headlight switch/dimmer switch just become relay controllers. You use the GM wiring to excite the coil in the relay. The wiring that goes to the lights and comes from the battery is 10 ga. stranded. When you turn the headlights on the relay gets energized and directs power right from the battery to the lights. There is a link in my computer at work that somebody posted a while back that contains a wiring diagram. I'll see if I can find it tomorrow.

I drove my truck after dark today for the first time since I did this conversion. I can't believe it took me 10 years to do this.

[Longhorn Man]

Read this...a great article on relays for your headlights.
http://www.classictruckshop.com/club...ead/lights.htm

[mrein3]

Originally posted by Longhorn Man
Read this...a great article on relays for your headlights.
http://www.classictruckshop.com/club...ead/lights.htm

That is the link I was thinking about. Thanks Longhorn Man.

[Huck]

Bet this would work for tail lights, brake lights, dash lights etc. Now to find a relay that will work----any suggestions--radio shack, etc.?
Maybe this explains why the 928Porsche's had 30+ relays located under the floor/firewall carpet on the pass side

[Old Dave]

Huck you can find these at most auto parts stores such as NAPA or O'Reiley's. They are a single pole double throw (SPDT) relay and a lot of the car manufacturers are using them. They are about 1" square, black, and usually have a mounting ear of some sort. Bosch and Potter-Brumfield are two of the manufacturers.

[BobbyK]

I'm just finishing rewiring my truck and did the relay thing as well.
Ya the lights are brighter.I'm waiting to get it on the road again at night so I can see the difference.

I used bosch 30 amp relays.You can get automotive relays at any parts store or local eletronics store.Usually $3-5 each.

It's a bit of a tagled mess here but.The 1st two are the high and low beam then the driving lights then the power distribution block.


I basiically ripped out all the orig. eng bay wiring and started from scratch.I used the orig. head light wire to "trigger" the relays but that's about it.
I ran some 12g wire from the relays to the headlights.This helps diliever more jiuce to the lights.

I also ran a 8g wire from the alt. to a distribution block on the firewall.This power distribution block now feed the whole truck and is remotely sensed by the alt.What that means is as the power is sucked from the distribution block the alt. sense wire connected there will bump up the alt. output automatically to keep all the circiuts happy.

Heres the 8g alt. wire with a 12g fusable link protecting it.


I have loads more pic's but this isn't my post.
I'll make my own post when I've completed things.:p

[Yukon Jack]

Interesting, my lights are so dim, this would be a great upgrade.

[Longhorn Man]

Jack, if you were to clean up the grounds on your front end, you'd be amazed at the light you'll get even without the relays. (I still plan on doing hte relays...but my truck lights up the road better than my wife's 96 Contour)