haultruck

So I finally got this ol truck put back together the other day after redoing the electrical from bumper to bumper. The p.o. had it in the worst mess I've ever seen. It was my first time tackling something like this, and there's no way I could have done it without this forum. Anyway, I pulled the light switch out for a try and no smoke, no fires. That made me happy. All the lights worked except two running lights on the flatbed, and one cab light. I didn't have replacements at the time, so I checked them with a test light and confirmed that I just needed a couple lights/ lightbulbs. Cool! I was excited and took it for a drive. High beam, low beam, brakes, and blinkers all worked as they should. Great. So yesterday I got around to replacing the lights and bulbs that weren't working. When finished, I pulled the light switch and every single light came on.... for a minute. All running lights went out. Checked fuse, and it's blown. Looks to be about ten years old anyway so no biggie. Replace fuse and a couple minutes later it blows. All out of 20a so I throw in a 30a. Same result. Today I spent all day checking and searching for a problem, and I can't find one. Why was my test drive with a couple less running lights ok? Could it be that there is no problem, and there's just to many lights on one fuse? How many is to many? I'd appreciate any thoughts. Thanks guys.

rrgrassi

That or a short somewhere. The fuse is there to protect the wires. You should never use a bigger rated fuse.

Check current draw as well. You may have a bad switch.

If you relay your headlights, that will lessen the current draw through the switch

Smokin$$away

IF I was doing this I'd undo the lights that were not working and see what happens before I start hunting buggers. They worked ok the you fixed the 2/3 lights and now problems happen. If that works hook up one light at a time and see what happens. Good luck!!

TJE

This is solid advice....I found out the hard way! like to have melted the whole thing down. I know the wiring on these trucks can be a nightmare.

Good luck, Tony

cdennyb

Yep, sounds like the two or three you had originally that didnt work are the reason it's blowing fuses now. look there.
Maybe when you put on the lights, the rivewt or screws are touching a hot terminal inside the light.

haultruck

I did this once before I posted and couldn't find a darn thing, after reading your reply,I decided to just tear in to it. On the running light furthest from the plug on the frame, (one of the ones that didn't work initially) there was a zip tie holding a good clean wire up out of the way. Everything looked good. Upon further inspection, I realized someone had used tie- wire the first time and it had cut almost all the way through the wire, and was hiding behind the zip tie. Easy fix, 20a fuse back in the fuse panel, and everything works great. Thanks for the input.
While we're on the subject though, how much power can you run through one spot before you would build a relay harness, or a power distribution center of some sort?

torquefan

If there are several extra lights wired into the circuit, I would strongly consider powering them through a relay, knowing that the factory lights are pretty much all the load the switch can handle.

Smokin$$away

After reading Jim Lanes thread on headlight relays ect. I think this should be on every vehicle made!!!

Guardrail

It depends on the light. Incandescent lights draw about 1 amp each. LED lights draw about 1 10th of an amp.

Guardrail