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hi club - newbie here - i have a new project of a 66 short bw that right now lights will do not work -- i changed switches but nothing -- where to go now -- is there a relay ?? or just chase wires ?? thanks for any help

Welcome from Ok. Time to break out the test light and see whats up. If it's factory there is no relay. Are you saying no lights, no headlights, no tail lights, no parking lights, what?

no lights at all - tail or head lights == i am not a wire chaser as such - that is why i ask in case of a point to start

I would start at the fuse panel.

You nay have a blown fuse.

Radio work? Truck starts?

Have you checked your grounds?

pics of the wire harness and under the dash would help us a little.

truck starts and runs

New bulbs?

sorry, have to eliminate the obvious. :)

Trouble shooting electrical problems is not as hard as you may think. It just takes a little time and understanding of what you are doing. I will try to give you my best online diagnosis. I am a Journeyman Electrician so I have quite a bit of understanding about electricity in most of its forms.

Helpful tools:

Volt meter, if you do not have one, a test light will be fine.
Continuity tester. If you do not have one you can make one. Get a battery, a rechargeable battery for a cordless drill would be ideal. Attach separate wires to each of the terminals on the battery (one per terminal). Now if the battery is charged, when you touch the 2 wires together they will spark. Boom, instant continuity tester (we use this a LOT at work, LOL. Don't tell OSHA.).

Lets start with the basics. In this case your lights need a ground and a hot wire to work. The ground comes from your sheet metal or frame. Both of these items need to be grounded from your battery. Make sure there is a good clean contact when you are making these connections. The hot wire obviously comes from your switch, which gets feed from your fuse panel. Now this may be obvious to you, but I just want to make sure we know whats going on.

Lets start with your rear lights:

Your running rear lights will be the brown wire that runs from the fire wall down the drivers side of the frame. From the fire wall it goes straight to your light switch. Your light switch gets power from the fuse panel. the wire that brings power dark green.

Your left turn signal will be the yellow wire in the same loom. It runs from the fire wall to your turn signal switch. Your right turn signal is the dark green wire in the loom. It runs to the turn signal switch as well. Now, your turn signal switch gets power from the fuse panel. The wire that comes from the fuse panel to the turn signal switch with power should be purple.

Now that is 2 different power sources. Both of those 2 sources have 2 things in common, fuse panel and ground. There is nothing else that connects the 2 together that would cause an issue for both.

Lets move on to the front:

It is a similar thing up front. The running light get there power off the light switch, but all of the other lights up front get their power from the turn signal switch.

Out of your headlight harness, your high beams should be light green and your low beams tan.

Your running lights should be light blue.

Again, just like the rear, that is 2 different power sources. Both of those 2 sources have 2 things in common, fuse panel and ground. There is nothing else that connects the 2 together that would cause an issue for both.

There is a few possibilities on what is wrong. You can have 2 bad fuses. Your red wire on the headlight harness may not have power. You can have a butt load of broken wires. Or you have a bad grounding system.

My best estimate, the easy one, 2 bad fuses. You have at least 2 different circuits with no power. Check your fuses.

Second most likely option, bad grounds. This would cause the problem for all your lights. Double check your grounds, use your continuity tester at each light and see if you have continuity. Test it to the negative on your battery. While you are at the front, test the frame and sheet metal to the negative of the battery. Use one clamp of your jumper cables to get the negative of your battery to the rear of your truck so you can test back there. If you have no continuity to any of your lights just ground out your sheet metal and frame to the battery.

Third option, no power coming in to the fuse box. Since your truck is starting, there should be power coming in to your truck on the red wire coming through the fire wall on your headlight wire harness. But if you look at the wire diagram that same wire splits off in the loom, one goes to the fuse box. Another goes to the ignition switch. The last goes to the light switch. Double check the red wire in the headlight harness and make sure there is power. If it does not, that would be your problem. If it has power, check your fuse panel. If it has no power, open up your loom and check out where that red wire splits off. You mostly likely lost 2 of the splices. If your fuse panel does have power, see option 1. :)

Fourth option. A whole lot of cut or broken wires. Fix....... buy a new wire harness. :)

Great answer CSoliz!
Everybody should read that.

ok- looks like i got a long weekend ahead - rust what rust , i got electrical problem '''''

Chris S.

That write-up is astounding. Great effort and very informative. Thank you. :metal:

Mac. :chevy:

i been thinking -- if the lights all worked then truck sat up for a while -- with two hot wires one to front one to rear -- it seems it is a ground issue or a rat issue -- for it is a common ground right ??? wires dont break from sitting but a ground could corrode away??

If it is a ground issue it will be a very easy to see. Go to your battery, look at your negative terminal. Follow the wire(s) and see if they run to your frame and your sheet metal. Check each one of your lights and see if the ground wire is secured to the frame or sheet metal. If all looks good, you probably don't have a ground issue.

What are the things you have done all ready?

Have you check your fuses?

Have you checked and see if your bulbs are good?

Have you checked for power at your fuse block?

Have you checked the wire loom for chew marks?

How long has it been sitting?

And an important question, does your horn work?

Could be a bad switch.....most frequently used part of the whole system;).

Oh, and pictures!!! they help. Take some of your battery hook up, all the wires behind your driver side headlight in the engine bay and your wire harness underneath your dash.

Quote:

Originally Posted by protrash64 (Post 3171017)

Could be a bad switch.....most frequently used part of the whole system;).

JanJ said there was new switches installed.

oops........got reading everything else :lol:.

Had the same thing happen to me , found out the switch for high beams was bad. ................Kirby

Quote:

Originally Posted by l79m20 (Post 3173368)

Had the same thing happen to me , found out the switch for high beams was bad. ................Kirby

dimmer switch??
it wouldn't effect the tail lights.......just the headlights

got windsheild wipers working !!!! still puzzled