only 8.5 volts to reverse lights.

[Crashtest84]

As stated I am only getting 8.5 volts to the reverse lights. I tested the fuse and there was 12volts there. So is there something in the switch that would cause this? How does the reverse switch circuit work? I know the switch in the trans is just a ground "m5od" any ideas on where I could be getting a voltage drop?

 

[Crashtest84]

I guess im always the one with the weird stuff no one has an answer for .

 

[RonD]

On the '90 wiring diagram I have it shows the reverse lights powered via the trans switch, not grounded.
That's for auto or manual trans.

So I would test voltage at that switch.

Black/pink wire from light to switch, purple/orange from switch to fuse, looks to be the #5 fuse

 

[Crashtest84]

Thanks going to go check it out now!

 

[Crashtest84]

Got a little troubleshooting done. There is 12v at the switch on the trans. after cleaning it I was able to get 9v to the lights. So for whatever reason I have a voltage drop after the switch. But that wire runs to unknown places in the truck first lol.

 

[RonD]

Well if you are not the first owner of the '89 Ranger then previous owners may have added/changed tail light wiring for using a trailer...............

The reverse light wire is part of that harness and may have been spliced and then "repaired" since it wasn't needed for trailer.

So that is where I would start, at the back.
Usually the tail light wiring comes from the drivers side frame rail and that's the most popular place to splice into the wires for adding trailer lights.
Wiring diagram says Black/pink wire is the color code.
It also has a factory "splice" since the 1 wire feeds voltage to two light sockets