Wiring issues 74 Fj40

[Tdeb44]

Hi all - after the last week of failures thought if ask the group about a wiring issue I'm dealing with.

Initially everything was working as you'd expect. But a few weeks back I made the following changes to the lights that has caused some issues:

Replaced the headlights with LED bulbs
Replaced front signal lights with LED bulbs
Removed the license plate holder/light
Replaced the tail lights with LED lights

When I made these changes it resulted in the signal lights no longer flashing, and I was not able to turn the headlights on because it would turn my tail/brake/signal/reverse lights off.

So this week I've made the following changes

- Reverted back to the original tail lights with the original bulbs
- Added load resistors to the front signal lights

And now I've run into the issue of nothing working with the exception of the brake lights and the side running lights. Still have the issue of headlights on then brake lights are off. So I'm further back now than before

Any advice on what I could check next would be appreciated. My suspicion is that I've lost a ground wire along the way somewhere.

 

[ToyotaMatt]

None of the factory lamps on a 74 have a dedicated ground wire

only have a B+ leed

they rely on the fasteners to the steel chassis to provide the neeed NEg- ground side circuit

This translates into none of your led bulb updates or upgrades are fully polerized as now needed by the LED bulbs

you need to be very creative and add a 2nd ground wire directly to the steel lamp housing then to a known good ground signal wire fed directly from your neg battery terminal itself

do not rely on a simple screw or pop Rivet to you chassis this will fail in short order or simply never work as intended from the start

you need to create a mini ground side sub harness and run it completely around your truck all lamps and lightshence tying it all together in a monilithic
Format or style to achieve your desired led equipped end product results as intended

 

[Toyo_Judson]

@ToyotaMatt, besides the grounds, do the LEDs have enough amp draw to heat up a bi-metalic flasher? I have LEDs for the rear brake lights and in the winter, they marginally work, when warm out they work better. I have OEM lights to go in so I should have some empirical evidence soon to support this thought.

 

[ToyotaMatt]

@ToyotaMatt, besides the grounds, do the LEDs have enough amp draw to heat up a bi-metalic flasher? I have LEDs for the rear brake lights and in the winter, they marginally work, when warm out they work better. I have OEM lights to go in so I should have some empirical evidence soon to support this thought.

you need to contact @Coolerman , he offers a high quality Digital swap out simple flasher relay now correct for a land cruiser


forget the 4 heat sinc's that's a huge waist of time and 4 parts that will eventually fail verse only one quickie plug and play part u swap in 30 seconds of less

if you follow me

 

[Tdeb44]

None of the factory lamps on a 74 have a dedicated ground wire

only have a B+ leed

they rely on the fasteners to the steel chassis to provide the neeed NEg- ground side circuit

This translates into none of your led bulb updates or upgrades are fully polerized as now needed by the LED bulbs

you need to be very creative and add a 2nd ground wire directly to the steel lamp housing then to a known good ground signal wire fed directly from your neg battery terminal itself

do not rely on a simple screw or pop Rivet to you chassis this will fail in short order or simply never work as intended from the start

you need to create a mini ground side sub harness and run it completely around your truck all lamps and lightshence tying it all together in a monilithic
Format or style to achieve your desired led equipped end product results as intended

Okay so on your suggestion I'll reinstall the rear lights with original halogen bulbs and I'll start by running a ground wire just to the front signals which are LEDs. There's a ground wire from something else that runs past both front signal lights so I think I'll throw a t-tap in there to see if that fixes my problem.

I went out this morning and realized now that since there isn't a ground wire for any of the lights, the load resistor I added was going between the signal light and the side signal light effectively shorting it out.

Clearly a newbie to doing any wiring so you mentioning the lack of ground wiring from signal lights to the negative on the battery is a gamechanger for me.

 

[hobbes]

For an LED relay (I use one on my 74):

Cruiser Wiring
then select Flasher Relays/Adapters on the left, then Turn/Hazard (LED) Flasher Relay Kit.

It also helps with some grounding issues, which is why I recommend Coolerman’s even to those without issues. Saves future headaches and very reasonably priced.

 

[ToyotaMatt]

Okay so on your suggestion I'll reinstall the rear lights with original halogen bulbs and I'll start by running a ground wire just to the front signals which are LEDs. There's a ground wire from something else that runs past both front signal lights so I think I'll throw a t-tap in there to see if that fixes my problem.

I went out this morning and realized now that since there isn't a ground wire for any of the lights, the load resistor I added was going between the signal light and the side signal light effectively shorting it out.

Clearly a newbie to doing any wiring so you mentioning the lack of ground wiring from signal lights to the negative on the battery is a gamechanger for me.

Do you have front amber small square apron lamps above fenders ?

or

rear red color side markers on rear quarter panels
By any chance ?

 

[Tdeb44]

Do you have front amber small square apron lamps above fenders ?

or

rear red color side markers on rear quarter panels
By any chance ?

I swapped out the front apron lamps for some LED lights I found cause original ones were pretty beat up.

And I still have the red side markers on the quarter panels.

Attached photos of both.

 

[ToyotaMatt]

do you have the small apron amber lights same size as red ones above fender ?

i cant tell ?



like these ?

 

[ToyotaMatt]

are your red side marker metal housings rears rusty or clean still ?

 

[Tdeb44]

are your red side marker metal housings rears rusty or clean still ?

1. No, my model doesn't have the amber lights like you sent. Only the signal lights that sit on top of the fender that I sent a picture of.

2. These are quite rusty, I'm having trouble getting bulb out even. Attached a quick photo below.

 

[Coolerman]

You need to do the following:
Go through ALL the light housings and clean them up. You will never get this to work if all your lights look like that!

Tip: A soak for 20 minutes or more in white vinegar and a wire brush will make a world of difference. Rinse them WELL, let dry and paint with reflective aluminum paint to restore the light reflection. Then follow ToyotaMatts suggestion about grounding all the light housings.

Next would be to pull the fuse panel, disconnect the connectors from the back, then give it a soak in vinegar for about 10 minutes and use a Dremel type tool with a wire wheel to polish the fuse clips until they shine. Re-install it and install all NEW fuses.

Then disconnect the battery cables, clean the terminals and the battery posts. Go to the other end of the battery cables and clean those connections.

After you have done all that THEN start trouble shooting your issues. Any weak link in this electrical chain will have you chasing your tail for hours...

The LED Flasher Kit will go out today!

 

[Tdeb44]

Hey guys - spent the last few days slowly plugging away at all of the above, looking forward to getting that flasher here to install!

Although, I ended up running into another wiring issue. I started it up just to let it run for 20 mins while it's sitting in the garage and after about 10 minutes it turned off. When I investigated I could smell burnt rubber and one of the wires that runs from the positive battery terminals that lead to the electronics in the cab had shorted out, burnt out and also turned the truck off.

Fast forward to today, I replaced the wiring and started it up. Typically when I start it, I have to pump the gas a little bit before it can run on its own. But today I needed to pump the gas for 5 mins and then it still cut out. When I tried starting it again it just cranked but wouldn't start.

Any thoughts on what I might have changed that would result in this?

 

[hobbes]

Stock or electrical fuel pump? Also check your idle solenoid.

 

[Dizzy]

Install an inline fuse, or a fusible link at the battery positive if you are going to tap into things there.

Use a fused wire for all jumper-wire troubleshooting, or trail spare.

 

[Tdeb44]

@Dizzy recommend any specific amperage for that inline fuse? I assume too low and I'll blow it constantly and too high and it won't do much to protect anything.

@hobbes it's the stock mechanical pump. The solenoid tested to work but it's seems it's not getting power so I suppose thats my issue there.

Any recommendations for figuring out where that power loss is happening would be great.

 

[hobbes]

Coolerman’s website has the schematic for your year.

See this page: Coolerman's Electrical Schematic and FSM File Retrieval

You will want to trace the idle wire to the fuse block and follow Coolerman’s recommendation in post 12. Also check the wire for continuity. If you need to replace any wires, Coolerman’s website has it for sale in the correct color code. Sticking with the right color helps future troubleshooting (and it’s so cheap why wouldn’t you?). I also purchased a quality wire crimper from him for some work I needed to do.

 

[hobbes]

If you don’t have a fusible link, I’d install one ASAP.

Cruiser Wiring. Then go to “Fusible Links” on the left side.

 

[Dizzy]

I'm no expert at sizing fusible link. I'm stuck working on this on my Nissan. The best answer I've found was relative wire sizes. Like if you have 16-guage, put a fusible link a couple of sizes smaller than it, which I only assume is an 18-guage. For a rescue, auxiliary, or test jumper, a 15-amp inline fuse seems reasonable for most work, because I only see not using an inline fuse unreasonable.

 

[hobbes]

Coolerman‘s website breaks it down what you need by year.