Looking for a Turn Signal Christmas Miracle! (1 Viewer)

BeerM3

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Morning all,

1/76 F40 and I'm stumped by a non-functioning turn signal issue. I've previously been able to sleuth out problems like this through similar q&a's in the MUD forums, but not this time. I've read through this thread several times
FJ40 Turn Signal Trouble shooting
as well as others that come up in a "turn signal steering column switch" search. Any help or insight would be greatly appreciated!! This is the last thing to fix before she's road-worthy again.

Here's what's been replaced:
  1. Wiring harness has been pulled, cleaned, and re-wrapped by me.
  2. New rear harness built by coolerman installed.
  3. The PO had a 40amp (yes, 40) fuse in the turn signal switch. The wire had melted up to the hazard switch plug. It didn't melt through the other wires, it just got hot enough to stick in a few spots. That wire's been fully replaced and with new wire & spades from coolerman snapped into the original plugs. Old connectors cleaned with a small screwdriver.
  4. Hazard switch has been replaced with another OEM match from MUD classifieds. It looks to be very clean.
  5. Steering column switch is brand new OEM.
  6. New fuse block from CityRacer
  7. New front and rear signal lights
  8. New OEM flasher from SOR (plastic replacement for the older metal version which i still have)
Here's what's been tested:
  1. Fuse is good
  2. Hazard lights don't work
  3. All other electrical parts work as they should.
  4. Power from turn signal section of fuse block to the hazard checks out.
  5. Power from hazard back to steering column checks out.
  6. I can't get any continuity from hot lead into steering switch no matter what position the switch is in.
  7. Headlight side of column switch works fine. Dimmer works.
  8. Power applied to the right terminals in both the hazard and steering column plugs do light the left or right side signals.
  9. Ran a testing pigtail from the battery negative to the steering shaft to see if the rag joint is supposed to be grounded with a jumper? I read that somewhere on here but can't recall if it's related to turn signals. Didn't make a difference.
So what's bolded at #5 is where I think i'm stuck. Like i mentioned above, the switch itself is brand new and bolted right in. Most of the usual suspects are brand new. I've got my mechanic looking into it right now and of course he's more savy than me with regards to troubleshooting electrical issues, but when he last looked at it he was stumped at the steering column section too. We'll have to pull the wheel again to get a better testing approach for the actual switch, but any "I've been there have you checked _________?" advice would be appreciated!

Thanks,
BeerM3
 
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Coolerman

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What year is this truck?

Early trucks:
The early Hazard wiring is different from the later trucks and there is a SEPARATE 10 Amp fuse in a plastic housing taped to the main harness that feeds power to the Hazard Switch.

Later trucks:
So if your turn signals work then you know the turn switch, bulbs, grounds, and flasher are all good. That leaves the Hazard Switch itself, or the fuse for the brake lights (second power feed into the Hazard Switch) as the culprit. When you pull the Hazard switch on it uses the brake light fuse to get power for the flasher, NOT the turn signal fuse. Both power feeds are GR wires!
 

BeerM3

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Joined
Aug 26, 2017
Messages
607
Location
Wamego, KS
What year is this truck?

Early trucks:
The early Hazard wiring is different from the later trucks and there is a SEPARATE 10 Amp fuse in a plastic housing taped to the main harness that feeds power to the Hazard Switch.

Later trucks:
So if your turn signals work then you know the turn switch, bulbs, grounds, and flasher are all good. That leaves the Hazard Switch itself, or the fuse for the brake lights (second power feed into the Hazard Switch) as the culprit. When you pull the Hazard switch on it uses the brake light fuse to get power for the flasher, NOT the turn signal fuse. Both power feeds are GR wires!

It's a 1/76. I didn't know that about the hazard also using the brake light fuse for flasher, which makes sense because that's not a keyed circuit...

Right now I have neither hazards with the switch pulled or signals with the key on and lever moved up/down, but i do have power coming to the hazard switch and to the turn signal plug. I can say for sure that wires to the lights are all intact and working when I bypass the hazard and column switch plugs.
 

Coolerman

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Paint Lick, KY
Turn Signals
Check this:
The after market flasher MUST BE GROUNDED.
You should have +12V on the Green/White wire going into the Flasher with the key on. (Flasher plugged up)
All the turn signal switch does is connect the Green/Blue wire to either the Green/Black wire (Left Turn), or the Green/Yellow wire (Right Turn). If the lights are grounded that will complete the circuit allowing the flasher to flash. If the lights are not grounded, the flasher WILL NOT FLASH.

Hazards
When you pull the Hazard switch to on, two things happen: You get power for the Flasher from the brake light fuse instead of the turn fuse AND you BYPASS the turn switch. The output of the flasher now goes to BOTH the GB (Left Turn) and the GY (Right Turn) wires so that all four lights flash.

It's possible that the Hazard switch is not allowing power to go through it. You may need to pull it apart and clean it.

A quick test would be to apply +12V directly to the GW wire going into the flasher with a jumper wire and either activate the turn switch or the hazard switch.
 

BeerM3

SILVER Star
Joined
Aug 26, 2017
Messages
607
Location
Wamego, KS
Turn Signals
Check this:
The after market flasher MUST BE GROUNDED.
You should have +12V on the Green/White wire going into the Flasher with the key on. (Flasher plugged up)
All the turn signal switch does is connect the Green/Blue wire to either the Green/Black wire (Left Turn), or the Green/Yellow wire (Right Turn). If the lights are grounded that will complete the circuit allowing the flasher to flash. If the lights are not grounded, the flasher WILL NOT FLASH.

Hazards
When you pull the Hazard switch to on, two things happen: You get power for the Flasher from the brake light fuse instead of the turn fuse AND you BYPASS the turn switch. The output of the flasher now goes to BOTH the GB (Left Turn) and the GY (Right Turn) wires so that all four lights flash.

It's possible that the Hazard switch is not allowing power to go through it. You may need to pull it apart and clean it.

A quick test would be to apply +12V directly to the GW wire going into the flasher with a jumper wire and either activate the turn switch or the hazard switch.

Good stuff Mark. Thank you. I'll do some more prodding and report back.
 

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