Taillight and Electrical Issue (1 Viewer)

[FatJackson40]

Specs: 1975 FJ40, 2F, mostly stock...

Wiring issues!!! Original wire harness. I am changing out my old taillights and can't seem to get them working correctly. When I hooked them up, the brake light would blink and the turn signal would stay solid. I've switched the wires around following the wiring diagram but can't seem to get the correct sequence. I've followed the wires going to the lights and have found where the wires split (passenger side engine bay near the firewall) and go to the back of the truck down the frame rail and where they go forward to the headlights and front turn signals. I'm thinking maybe there's a bad ground or a chaffed wire somewhere I haven't found yet...also, the headlights are very dim. Alternator is working correctly. Another electrical issue I'm having is the 2 Ammeter wires behind the dash console get very hot when the truck is running. I haven't noticed this before but when I was trying to diagnose the light issue I saw puffs of light smoke coming from the Ammeter wires. I'm at a loss. I hate chasing ghosts and I'm not an electrician. Any help is appreciated and I know someone out there in this group can probably help. Thanks in advance!

 

[ToyotaMatt]

i would suggest you get your taller then usual cup of coffee and digest this entire thread , your issue is discussed in-depth in here , start at post # 1 ....

no skipping around and cheating like that .........


,.

OEM Tail light / Lamp Electrical Connector Differences / Types FJ40 1/75 - 10/ 84 ( 8/26/2019 Final OEM TOYOTA Parts Solution Updates )

OEM Tail Light / Lamp Electrical Connector Differences / Types FJ40 9/73 - 10/ 84 i would like to Dedicate this Thread to my Friend & fellow member @Coolerman :) note: if anyone sees a factual error or has input to add please send me a PM so i can't EDIT any errors with a...

forum.ih8mud.com

.

.

OEM Tail light / Lamp Electrical Connector Differences / Types FJ40 1/75 - 10/ 84 ( 8/26/2019 Final OEM TOYOTA Parts Solution Updates )

OEM Tail Light / Lamp Electrical Connector Differences / Types FJ40 9/73 - 10/ 84 i would like to Dedicate this Thread to my Friend & fellow member @Coolerman :) note: if anyone sees a factual error or has input to add please send me a PM so i can't EDIT any errors with a...

forum.ih8mud.com

 

[ToyotaMatt]

 

[45Dougal]

The ammeter wires shouldn't be getting hot and definitely shouldn't be smoking.
This could happen for two reasons.
1- you have a permanent or intermittent short between the output wire and ground (the whole input wire will be hot).
Could be indirect via something like the wiper motor for example.
2- you have a poor connection at the ammeter crimp terminals (The high resistance caused by corrosion causes a local hot spot).

Hopefully it's the latter, and this will also explain your headlights.

The tail lights are easy enough to resolve with a voltmeter (since you have an FJ40, I assume that you have one - if you don't, then invest 10 dollars and save a lot of guessing).
Switch on each of the lamps in turn and test each wire for 12 volts. Possible that you swapped the ground wire with a feed wire, or could be a bad ground (bolt a new ground to the chassis).

 

[FatJackson40]

The ammeter wires shouldn't be getting hot and definitely shouldn't be smoking.
This could happen for two reasons.
1- you have a permanent or intermittent short between the output wire and ground (the whole input wire will be hot).
Could be indirect via something like the wiper motor for example.
2- you have a poor connection at the ammeter crimp terminals (The high resistance caused by corrosion causes a local hot spot).

Hopefully it's the latter, and this will also explain your headlights.

The tail lights are easy enough to resolve with a voltmeter (since you have an FJ40, I assume that you have one - if you don't, then invest 10 dollars and save a lot of guessing).
Switch on each of the lamps in turn and test each wire for 12 volts. Possible that you swapped the ground wire with a feed wire, or could be a bad ground (bolt a new ground to the chassis).

45 Dougal,
Thanks for the response! I will try your suggestions. I do have a voltmeter, should have been standard-issued equipment with the FJ40!
I will take a look and see what I find. Thanks again!

 

[FatJackson40]

ToyotaMatt - Thanks very much for the help!

 

[pb4ugo]

Your 75 Tail lights are grounded by the light housing to the frame, so the housing needs to be installed with good ground contact. I ended up making a ground wire strategically riveted to the back of the light housing and used one of the bolts that hold the stone guard in place at the back of the light for a grd. Coolerman sells the plugs, terminals and the correct color coded wire if you need.

 

[South Texas 97]

There is a ground about half way down the frame, approximately where the pax seat is, I think for the gas gauge float. Worth cleaning up while you are under there.
check the harness along the frame very well, mine had a fried or chewed section that was not obvious.
there is also a 5 or 6 pin connector back there that can get corroded pretty badly.
lastly @Coolerman has observed that the colors on the back part of the harness does not always correspond to the proper colors on the rest of the harness, so may be worth using the meter with an extension lead from the connectors on the firewall, and make sure continuity all the way back, and what color corresponds.

 

[pb4ugo]

There is a ground about half way down the frame, approximately where the pax seat is, I think for the gas gauge float. Worth cleaning up while you are under there.
check the harness along the frame very well, mine had a fried or chewed section that was not obvious.
there is also a 5 or 6 pin connector back there that can get corroded pretty badly.
lastly @Coolerman has observed that the colors on the back part of the harness does not always correspond to the proper colors on the rest of the harness, so may be worth using the meter with an extension lead from the connectors on the firewall, and make sure continuity all the way back, and what color corresponds.

Yep, My wires in the back were different colors after the plug. When things are acting strange it's usually a ground. I use and prefer a test light most of the time. I'll use a meter when I need to know voltages.

 

[45Dougal]

Your 75 Tail lights are grounded by the light housing to the frame, so the housing needs to be installed with good ground contact. I ended up making a ground wire strategically riveted to the back of the light housing and used one of the bolts that hold the stone guard in place at the back of the light for a grd. Coolerman sells the plugs, terminals and the correct color coded wire if you need.

Most of my mounting screws were hanging by a thread, so I drilled them all out and fitted m4 rivnuts. Getting a good earth now