71 F100 Lighting Issue

[jeki2793]

I bought a F100 yesterday and had a Taillight Issues which means I had none. I replaced the bulbs and it worked. I went out today and started the truck and drove off and noticed my headlights dimming in like a blinking pattern. I stopped the truck and noticed all the lights were doing it and I had no running taillights. I have Brake, Turn Signal and Hazard Lights on the rear just no running lights and the others are all blinking. I took out the driver side taillight because I noticed corrosion on it yesterday an cleaned and replaced it and all the lights worked till I started the engine and it started blinking again and lost the running lights on the rear. I am new to trying to work on a older vehicle and would greatly appreciate any help you all may offer.

[sargentrs]

First I'd check and clean the grounding points on the parking/tail/turn lights and housings. Next I would go ahead and replace the headlight switch and the dimmer switch and eliminate those gremlins right away. Testing the various circuits and such is tedious and time consuming. Cost you about $30 and take about an hour. Both are notorious lighting culprits. The last gremlins would be the turn signal switch or flashers. Before I tear into that, I'd do some serious troubleshooting but the others are cheap no brainers.

[basketcase0302]

And pay particular attention to ALL your grounds:
1) Main ground wire from the battery to the engine block.
2) Ground strap from the intake manifold to the truck cowl (lot of time folks have tossed this one in the trash-big mistake)
3) Ground on the steering column under the hood (ties both halves of the steering shaft u-joint together).
4) Ground strap that ties the front top of the frame rail to the radiator support.
5) Like Randy said-clean thoroughly all lighting sockets ground eyelets and where they attach to the body!

All of that and like Randy said the headlight switch, (which has a built in circuit breaker) is a good start. Then go out towards the battery condition / alternator, (you can have the charging condition tested for free at any autozone / o'reilly / discoount auto parts store and the voltage regulator.

Do you have a digital voltage meter and know how to read it? That will help tremendously!

[Thipdar]

I bought a F100 yesterday and had a Taillight Issues which means I had none. I replaced the bulbs and it worked. I went out today and started the truck and drove off and noticed my headlights dimming in like a blinking pattern. I stopped the truck and noticed all the lights were doing it and I had no running taillights. I have Brake, Turn Signal and Hazard Lights on the rear just no running lights and the others are all blinking. I took out the driver side taillight because I noticed corrosion on it yesterday an cleaned and replaced it and all the lights worked till I started the engine and it started blinking again and lost the running lights on the rear. I am new to trying to work on a older vehicle and would greatly appreciate any help you all may offer.

I think you may have more than one problem. Maybe not.

All lights blinking, including headlights makes me think of the headlight switch, but it's acting like it is supposed to - the switch's circuit breaker is cycling. The reason it's cycling is probably due to a short.

What year truck is it, and does it have gauges or idiot lights?

[ottocilindri]

noticed all the lights were doing it and I had no running taillights. I have Brake, Turn Signal and Hazard Lights on the rear just no running lights and the others are all blinking.

I'm having same issues, headlights are ok.
Just blinking parking lights and taillights sometimes not working at all.

Replaced light switch but nothing changed, can't find any short.

How you solved the problem?

[Nitekruizer]

I would also suggest checking the fuses, if you haven't already. Sometimes, if there's a blown fuse on one circuit, the power will try to find it's way through a different path. This can cause all kinds of strange things to happen.

[Thipdar]

The other thing that comes to mins is that the alternator belts may have a little slack in one or the other (or both).

Also, you might want to test the diodes in your alternator - if one's out, the system may be trying to rectify 2/3 of the cycles it needs.