No headlamps after switch on main beam

[Ukjimmyfan]

Hi, just doing checks before using the truck.
Headlamps etc came on ok.
Went to main beam ‐only sidelamps and indicators now!!!
Touched nothing within Headlamp wiring
Ideas please.
Just fixed wiper short(see other thread)..........bypassed all other wiring.

 

[Barrman]

What year truck? Trying to figure out floor or column mounted dimmer switch.

Either way the headlight power goes from the headlight switch to the dimmer switch. The dimmer switch then sends power to either the high beams or low beams. You will have to test for power at your dimmer switch. Basically, power should be at 2 of the 3 wires of the dimmer switch anytime the headlight switch is on.

No power, go test at the headlight switch.

Power to the dimmer and power out to low and hi beams when switch for each. Go test at the back of the headlights.

If you get power all the way to the headlights your next reasonable step is the headlight ground bolts. Find them, take them apart, clean them and put them back together. After that look at the bulbs being bad.

 

[Ukjimmyfan]

Hi, barrman.
Definitely floor mounted dip switch-1982.
I will go through that step by step an report back.
Wiring is not pretty and I sorted it but never had it blank out like this suddenly, like as soon as main beam switched on.
There are 55w driving lamps. I wired those carefully and in use years.
There are no dashboard lights so maybe there is a clue.
If it is as simple as a switch I would die laughing!

 

[Wes Harden]

Dash lamps get power from a differnt sorce. The dash lamp fuse. Head lights are battery hot from fuse links.

 

[Barrman]

Yes, dash lamps and tail lights are on their own fused circuit.

Normally when something just “poof” stops working it is a connection that fails.

 

[Ukjimmyfan]

Hi barrman,
All the fuses from the fuse box were pulled.
A couple corroded but not awful.
Changing obviously made no difference.
There was a silver box neat the top but this wasn't a fuse it just contained contained windings/contacts.
What the large black plastic thing is with like a speaker grille above that I've no clue.
I will try to locate the fusable links.
Where is the relay? Probably can feel flasher unit clicking. Unless there is no relay so headlamp switch burns out easily...
I don't want take the dial binnacle out for the 4th time if switch is bad.

 

[Barrman]

Have you tested for power anywhere in the system as I suggested in post #2?

 

[Wes Harden]

The round silver thing is the turn signal flasher

 

[Ukjimmyfan]

So there is no fuse for headlamps like a normal car. Just a Fusable one in line by starter and then inside the switch.
There is no power at headlamps (H4 x4)...
Not good at night!
So if the headlamp switch is duff I'd like to bypass it with a fused jump wire to check .
Ideas please?
I've a switch that can take 50A for that.
Then ideally find a 100% indestructible universal switch for headlamps
Dash lights straight to 12v no wonky dimmer.
Put in high amp relays and wiring to all four headlamps (as should have been done at factory).
I've cleaned and refitted the floor dip switch. No way to get inside to look.
Google is saying this is in the top 10 of squarebody annoying fails....

 

[HankScorpio]

Stop screwing around with google and get a test light on it. The headlight switch can fail, happens all the time. Without checking for actual voltage along the system you are just wasting your time.

"I've cleaned and refitted the floor dip switch. No way to get inside to look."
Pretty easy to check the wires with a test light, then there is no need to get inside. Same goes for the headlight switch.

You don't need any fancy voltmeters to get this figured out. Just a lightbulb.

 

[Ukjimmyfan]

I didn't really do anything.
To make sure I had some lights I put the extra driving lamps on a switch instead.
All the headlamps are on again!
Pics of how to fit relays to the factory lights and what was used please?