1974 f250. Auto.

At the turn signal flasher. The connector has TWO wires. One orange with a yellow stripe. One light blue. I have 0V on BOTH wires at the flasher at all times. Running. Key on. Key off. Any transmission position.

The available wiring diagrams from fordification are great however they can be very difficult to follow.

Can ANYONE tell me the exact path of voltage from the source to the turn signal bulbs?

All fuses are NEW. Tested for voltage on each side AND continuity on the bench with my fluke meter.

Both flashers are NEW.

Battery has a full charge and will start the truck.

I have jumpered the circuit from a 12v hot source to both the orange and the blue wire. The blue wire gives a solid turn indicator on the dash and bulbs with NO BLINK. The orange wire operated the turn signals normally.

 

The battery / alternator supply power to the ignition switch from the starter relay (connected to the battery) using a red/green wire. The all powerful ignition switch has a path to the fuse box to supply juice to it in RUN, or START, or ACCESSORY. using a black/green wire.
At the fuse box, a 15 amp fuse supplies juice via orange/yellow wire to the flasher when the key is turned to RUN,
then when a load is present on the blue wire, it is allowed juice in spurts (flashes) to the turn signal switch.

A load is created when the turn signal switch is moved to either left turn or right turn. When either one is selected ... a short controlled circuit through the bulb filament to ground creates a path to ground, and that is a "load". If a left turn signal is selected, the switch creates a path from the blue wire to the yellow/black wire to two left signal bulb filaments ... plus a small left side indicator bulb filament in the dash instrument cluster. When a right turn signal is selected, the switch creates a path from the blue wire to the green wire to two right signal bulb filaments ... plus a small right side indicator bulb filament in the dash instrument cluster. Until a load is created, the flasher will not flash.

 

If I followed the wiring diagram correctly...follow the orange-yellow wire from turn signal flasher to the wiper switch (power for windshield washer)....should be in same terminal as white-black wire...follow that to the reverse lights switch...there should be a black-red wire coming off that switch (in the same terminal) which goes back to the fuse block.

Make sure the clips are clean and corrosion free. it is also possible the crimp connections for the black-red wire on the back of the fuse box are corroded.

 

unfortunately in 74 the orange/yellow wire does NOT originate at the fuse box.

 

I have 12v at the orange/yellow wire at the wiper switch. Which. Also has intermittent wipers, so, there is a delay installed. This means, from the flasher, O/Y to the wiper switch connector, that connector plugs into, a second connector to the delay, from there to the switch...

I will continue to investigate more. Two weeks. I have most of the dash dismantled and 1/3 of the wire loom removed.

Still no 12v to the blue or the orange/yellow wire at the flasher. The only terminal of the turn switch that has 12v is the white/red

 

Just going by the schematic posted. I pulled it from here long ago. It said 74-78, but if wrong, perhaps this will help?
.1973-1979 Ford Truck Wiring Diagrams & Schematics - FORDification.net

How many fuse positions are in your fuse box?

 

It is appreciated! Don't mistake my frustration with this truck 😂

6 fuse positions. It's the smaller fuse box in these trucks.

I have struggled to find accurate or clear wiring diagrams. The copies at fordification are very helpful. They are also close. But I'd say... 90%. That 10% has me scratching my head.

With that. My paper, original copies of the Ford factory repair manual, does not include wiring diagrams or electrical troubleshooting guides.

 

All that said... It is very difficult for me to identify the load and source side of the blue and orange/yellow wires being that they are in series with several other loads.

I am on the verge of replacing the wiper switch and delay... However. If I can avoid shelling out 150$ for those parts, which are in limited supply, id like to.

 

You meant 5 fuse positions maybe?

Those copies on Fordification look to be reduced copies or scans of the larg fold out factory schematics. The wires may change colors in the smaller fuse box, but I don't see any reason to change circuits.

I know it can be frustrating. I know some look down at Hayne's, etc ... but I find they help.

In post #4 ... I meant to ask where it went?

 

OK,,looking at Haynes (pgs 203-207, #788titled "FORD PICK-UPS & BRONCO,1973thru 1979 six cylinder in line and V8 models F-100 thru F-350") for 1973 which would have the 5 fuse position box, looks like the orange/yellow goes to the plug windshield wiper/washer switch to tie into a white/black supplying power there & C-581 and then the white/black wire goes to the NSS black/red wire which itself goes to a 14 amp fuse in the fuse box.

The fuse connects the black/red wire to a buss bar (same buss bar also supplies the 30 amp fuse) ... which is fed by a black/green wire that eventually looks to lead to the ignition switch and a leg goes to the alternator warning lamp, etc.

If your windshield washer works, I'd look between there and the flasher socket.

The blue wire from the turn signal flasher goes to the turn signal / emergency flasher switch, it is the load side according to this.

The various Haynes pages are miniature versions of the large original Ford schematics. I have the original 7 page set for 1973, but they are big ... each page is like 6 pages.