1973 Ford F100
the following lights do not work: high beam headlights, turn signals, hazards & brake lights
What could be my issue with the listed lights not working???
what I have done to try & fix them: new turn signal switch, headlight & dimmer switches, 4 new 1157 bulbs, voltage regulator, alternator, cleaned all grounds, checked all grounds, new headlights, instrument cluster voltage regulator, new fusible links to starter solenoid.

 

Did you check fuses? Well the battery pwr goes direct to the headlights (via the switch) to work with the truck not running. No key on ect, same for the brake lights. So I suspect a wiring issue. Yes the headlight switch has a internal fuse. I believe when you have NO power to the truck at all the 1st suspect part is the fusible link. Did the battery or jump start box get connect backwards by chance? What were you working on when this happened? Stereo and AMP install?




TS and hazard flasher 101: https://www.ford-trucks.com/forums/1...l#post18338355

 

Well, first of all, welcome to FTE!
Second of all (really should be the first thing), stop replacing parts!
Doing so without more testing only adds more potentially bad parts where they may have been working prior to this and have nothing to do with your issues.
Could be several, unrelated items. But it's for sure not just one thing, unless your body is not grounded. Even then though, it might be multiple ground points.

All are legitimate thoughts, but a waste of money if you did not test each one first. Some are very easy to test as well

VERY good in almost every electrical problem scenario.
Did you verify that your battery has at least two ground wires? Should be the main cable to the engine, AND a wire (at least 10ga) to the body somewhere nearby.
Have you been able to verity that you have power to every point in question? And for turn signals and 4-way hazard flashers, there are two separate flasher units/relays under the dash that could be at fault.
Along with other stuff...

​​​​​​​Sorry to say, every one of those was wasted money. None of them could possibly have anything to do with any lights not working.
Does the engine run? Does the battery stay charged? Do the gauges work? Does anything else work? If so, then none of those was necessary, and I hope you did not throw away the old stuff yet.

Reason we're always rambling on about new parts around here, is that many of them are crapshoots and can be bad right out of the box. And still more will fail very soon after...
So it just adds more potential problem areas to add new parts. You can no longer assume that just because you replaced a part with new, that you have guaranteed that you no longer have to test that part. It used to be possible to do that, maybe 30 years ago. But in the last 20 years or so, the quality of parts has dropped so much, that it's disheartening even to the most stout heart.

So do some more testing and hunting and tracking and tracing.
Do you have a volt-ohm meter? What about a test lamp? A meter is better and more versatile, but a test light can still tell you some basics.

Paul

 

The only wires on the truck that are in bad shape are the 2 wires going to the solonoid that say S & I where the 2 wires plug up at. The rubber coating has came off them like they got hot before maybe.there is 1 ground wire I have not checked and that is from valve cover to firewall. Don’t know why I haven’t checked it but I haven’t! lol, I did replace both flasher relays. My test light wouldn’t work when I brought it to the truck and my volt meter could not be found! So I was out of luck on those things. Could it be those 2 wires going to solonoid?

 

Unfortunately, no. They have very limited functions and are in a completely different area.
The “S” terminal should have a red wire with a blue stripe. It’s the wire that when you turn the key to START causes the starter relay/solenoid to energize, and the starter to crank.
The wire on the “I” terminal is brown, and is connected directly to the ignition coil via the plug at the back of the engine. It’s for providing extra voltage during the start cycle.
Nothing to do with light unfortunately.

 

Get a good test light or 3 and place them in different areas (truck, tool box in garage next to meter, 3rd?)

The first thing I would do is pull ALL FUSES and clean the holders and the fuse ends.
They get a funk on them an dont let power thru.
I would also check them with a meter (next to test tight in tool box?) if good or not before putting them back.
I have had some that look good but was broken on the ends inside can could not be seen.

Pick 1 thing to work on at a time head lights or brake lights?
Head lights when on do the head light light up or is it the dash hi beam that dose not light up?
If the head lights switch on and test light in hand at the dimmer switch pull the plug off and check for power at the plug.
1 wire should have power the other 2 go out to the bulbs (1 low other high).
If no power you need to go back to the switch to find out why.
Do your trucks have issues at the fuse box (back side) of melting the wire that supplies power to the head light switch?

Brake lights, check for power at the switch, 1 wire is power in the other is power out.
If no power you need to look back at the fuse box.
If you have power in push the pedal do you have power out?
No power out replace the switch and yes the new switch could be bad.
Do not get the 2nd switch from the same place and brand.
If power out you need to move up to the turn signal switch for more checking.
Dave ----