big problem!

[Tanker78]

I am having an issue with my lights or my charging system. When i turn my lights on only the head lights come on. No dash lights, No marker or park lights. and when ever i run the lights it kills the battries. I've changed the headlight switch and relays. I've checked the wiring and everything is tight. Battries are good and altanator is charging. I can't figure it out. If anyone has any ideas please let me know. It's a '99 F350 Diesel 7.3

[Roger45]

If you know the alternator is good, and your batteries have been stress tested, my guess is that you have a bad ground somewhere. Follow the black leads of your batteries from top to where they connect and make sure there cracks or breaks in them, and the connection is solid. If you suspect anything, change them out. You may want to remove them and take a wire brush to both ends before re installing them. Another thing to do is check both fuse boxes (under dash and under hood)...look for any blown fuses, also check for any indication of electrical arching between fuses. I bought my '99 recently and the previous owner had installed six exterior lighting systems (all separately installed and not linked)as well as other things and the fuse box is really interesting now ;-) Hope those two things can help some...

[Tanker78]

about the only thing i haven't done is check the grounds. I know i got to do it the only problem is it's only about 10 degrees out and it sucks to crawl around on the ground like that lol. thanks for the sugestions

[Mobetta]

Tanker, I am having same electrical issue. No dash lights or rear running lights. can't drive in the dark unless I turn on the flashers. Spent the day testing all the relays, fuses and light bulbs. Tomorrow going to start tracing wires for a short. Let me know if you find anything.

[Tanker78]

nothing yet but as soon as i do i'll let you know

[klhansen]

I don't think your problem is going to be grounds, as they're separate for each corner of the truck.

Here's a couple of wiring diagrams that might help you out. If you're getting power out of the headlight switch, then the next spot to check is connector C1045 (should be the middle one of the 3 in-line connectors on the fender liner underneath the master cylinder). Everything goes thru there to the running lights.

Hope that helps.

92-1 Exterior Lighting.pdf

92-2 Exterior Lighting.pdf

[Mobetta]

I think I located my electrical issue, broken contact in the Power Distribution Box. Fuse 8 slipped in and out with ease. No current going past fuse.
Now I need some direction how to pull the PDB. I have the service manual but could not locate any direction for proper procedure.
Will not know until I can get this repaired for sure.

[Tanker78]

i think i found mine. My uncle teasted my altenator and had the tester on the wrong setting. I should have done it my self but didn't. plus that center conection was loose so i push that back togeather. so once i get a new altenator i'll let you all know how it turnes out.

[Tanker78]

well the altenator was bad, but that wasn't my problem. the truck is not telling the altenator to charge. so i've talked to a few people and they seem to think its my PCM. i think its time to go to a gauarge. ****!!!!

[Tanker78]

Still have no truck but did get a suggestion from a guy through my brother. That a fuseable link might be blown. That idea compleatly sliped my mind didn't think they were still useing them at that time. Fingers crossed

[rock_doctor]

Another owner was having a funky head light issue and he found a short in the harness as it passes over the turbo. Apparently either the heat from the turbo melted something or something got pinched during a repair. Maybe take a look at this loom...

[Mobetta]

Tanker it was not the connection, I found a corroded wire in the engine compartment just before it went through the fire wall.