So, driving home 30 miles in the dark with no lights on the dash was, shall we say, interesting...

No lights in the cluster of gauges, gear indicator, wiper/lights legend, heater controls.

Do all of these come off the main light switch and then spread out to the various points, so one wire to the gear indicator, one(?) to the heater controls, one(?) to the lights/wiper legend, and one(?) to control the two bulbs in the dash gauge cluster?

I assume that I will have to check:
a) fuse (3A in the fuse block to left of steering column)
b) bulbs (no reason why they can't all be blown, I suppose..)
c) contacts on light switch
d) wires connected
e) condition of Mylar box and PCB (speedometer, fuel gauge, water temp work, oil pressure does not, not sure on ammeter which might imply that the PCB itself is, in general, OK)
e) condition of bulb to holder contacts

If new fuse added and blows immediately, check for ground issues

 

Check to make sure your interior lights dimmer switch (turning light switch ****) has not be turned to low. This is an often overlooked simple issue. Could also be a bad switch as well.

Else wise, here's a link to some helpful diagrams. 1973-1979 Ford Truck Wiring Diagrams & Schematics - FORDification.net

 

I would take a look at your instrument cluster fuse. Look at it extra closely or poke both ends with a test light because they can LOOK good but still be bad. Sounds like the internal rheostat in your headlight switch is junk though to me.

 

I believe the dimming control of all dash lights is controlled thru the headlight switch. Tuning it counter clockwise and right before you turn on your dome light (with the doors closed) should make the dash lights be on full bright.

X2 on ck fuse, if not might be a bad bulb on the back side of the cluster. But with them all out sounds like a fuse or a bad headlight switch.

 

I'm guessing that, where available, Motorcraft are the best option for parts like switches?

When RockAuto shows before serial number C 25,000, and the truck is A 31399, that would be the correct light switch (MOTORCRAFT SW1245 {#D3ZB11A685AA, D3ZZ11654A})?


Click link

And then this for the fuse?


Click link

 

I do not think you need the one with a spacer. Yes glass fuses.

You do know that you will need to remove the instrument cluster outer bezel trim (just a few screws) to get to the lock nut that holds the headlight switch in place.

Also you do know that there is a button to push on the switch body to get the headlight shaft and **** to come out.

And you need to disconnect the battery before you do this other wise headlights will be on the whole time.

Walk thru of it. https://www.ford-trucks.com/forums/1...l#post14880899

 

Thanks for that!

I'm coming to the Dentside world from air-cooled VWs, so lots to learn about the differences. I have no doubt that there will be lots of dumb questions to come, let alone getting my head around SAE instead of metric sizing

 

Welcome to FTE and the Ford truck world. No such thing as a dumb question, just and inexperienced one.

For the most part 3/8, 7/16, 1/2 and 9/16 open end wench and you have enough to work on these old trucks.

 

Here's the fusebox - at the very least, some emery cloth on the contacts wouldn't go amiss...

 

Then there's this red connector that currently isn't...

 

Connects to the seat belt buzzer. Buzzer should be mounted on the left side of the cab behind the dash. Probably disconnected on purpose..................

 

No worries, it should be connected to the seat belt buzzer...not fuel gauge related.

 

This switch is a KIT, comes with the spacer, but if not required, throw the spacer away.

D3ZZ-11654-A .. Headlamp Switch KIT (Motorcraft SW-1245).

This KIT replaced a gazillion different 1965/72 Ford/Merc Passenger Car; Truck & Econoline switches, so some will require the spacer, some will not.

And, even though the prefix (D3ZZ) reflects 1973 Mustang, the switch was not used on a 1973 Mustang!

1965/75 F100/350; 1976 F100/350 before serial number C25,001 // 1965 Falcon/Comet; 1965/66 Mustang & 1971/72 Mustang/Cougar; 1969/74 Econoline and etc etc etc.

 

No idea if it comes with it or not, I just know that you do not need it...

 

But if you want your seat belt light to illuminate, you'll need to plug in the module. I grabbed one at the junk yard and was pleased to see that it had no buzzer, but it did get my seat belt light to light when starting the truck.