Reverse light wiring question (1 Viewer)

[MDH33]

I have a 73 FJ40 and i've been slowly repairing all of the electrical gremlins. I have everything working except the reverse light. The 73 FJ40 has that big metal enclosured reverse light with the glass lens. It was missing when I rewired the back, but I recenlty found one and hooked it up, but it doesn't work. I traced the wires up the harness and I think the problem is with the switch on the trans.

My question:

There is a single Red and Lavender (RL) wire going to the light. There are two RL wires with male connectors coming out of the top of the trans. They were disconnected, but there are two RL wires with female connectors and a single red wire with a female connector coming from the main harness along the frame near the parking brake. I tried connecting the RL to RL and it didn't work. I'm wondring if the red wire is supossed to be connected to something involved with the reverse?? Anyone with wiring knowledge for this reverse set-up please respond. I'll post some pics if needed.


Thanks!!

 

[MDH33]

I hope someone can help with this. Electrical systems make me crazy!

I took a few pics. I know how rusty and smarmy it is , mechanicals and electrical first!!

Here's the Uber-cool '73 reverse light:

This is the rear wheel well and wiring going to the light from the harness:

This is following the harness up the frame to where the RL wires split from the harness near the parking brake:

This is where I plugged in the wires from the Reverse switch on the trans to the harness, RL to RL, still that extra Red wire:

This is the switch on top of the trans with two RL wires coming from it:

So how is it supossed to be connected?? My wiring diagram only shows single RL wires and no Red wire.

Thanks!

 

[Pin_Head]

There isn't much to it. One RL wire goes from the fuse block to the switch, so it will have 12 V on it when the key is on. The other RL wire goes from the switch to the lamp. The lamp housing is grounded, completing the circuit, when the switch is activated in reverse. Check for voltage on the wire and if no voltage, check the 5A fuse.

 

[Poser]

According to the wiring diagram, you should have switched 12V at one of the RL wires down by the transmission, and the other should have continuity to the rear lamp, as the lamp grounds to the body.




It is entirely possibly that a previous owner found the switched 12V source under the dash and spliced into it at one time, creating an open condition now...



Test lead the two RL wires with the key in the ‘ON’ position and see if you get any power down there....make sure your test lead is attached to a good known ground.


You should also be able to verify that the rear part of the wiring is good if you make a jumper wire from the battery to one of the two RL wires under the truck….your backup light should illuminate if you have power, continuity in the wiring and a good ground.



Just some ideas.....talking/typing out loud.



Good luck!


-Steve

 

[MDH33]

Thanks for the replies. I guess I'll dust off the multi-meter next.

Any idea what the stray red wire is for?

 

[Colorado Boy-74-FJ40]

been there

There is a switch that threads into the back of the transmission tower where the stick shift is. It is a plunger type switch. The reverse light wiring goes through it. The wires Red and lavender are a loop of sorts. One wire is hot from the ignition (not battery hot) the other gets energized when the circuit is completed when the stick shift makes the plunger depresses completing the circuit. This is the voltage that travels back to the reverse light. unplug the connectors in the picture. One of them will be hot when the ignition is turned on(Should be) the other will be dead as it is the one that runs to the light. Now check the switch side. Put a meter on the wires. Should read open when you are NOT in reverse. When in reverse you should get continuity. (mine was shorted internally) I ended up putting a lighted toggle switch on the dash for back up lights since a replacement oem switch was about $80.00

 

[MDH33]

Success!!

Thanks for all the replies. The problem ended up being a combination of the wiring being crossed and the light assembly was incorrectly grounded. Works great.

I still have no idea what that red wire is for.