Hello all,
My reverse lights have been cutting out over the last few months. They didn't work, then they did for a little while, now they don't. I checked the bulbs: good. I checked the fuses: good. I figure it must be the switch or the wiring. How do I check for sure? I'm not experienced at all in the electrical aspect of auto repair. I was hoping some of you could point me in the right direction for advice, resources, and equipment. Please and thank you!

 

Do you have a manual or automatic transmission?

They use different Reverse light switches

Manual will have a 2 wire switch, 12volts in on 1 wire(when key is on), other wire goes to Reverse light bulbs, when you put shifter in Reverse a tab inside trans on the Reverse shift rail pushes switch closed and passes that 12volts to the bulbs

Automatic has a Range Sensor also called a Neutral Safety switch(NSS) on the transmission's shift linkage, the same setup as above, when shifter is put in Reverse the switch is moved to connect the 12volt wire to the Reverse bulb wire.
There are a few other wires on this switch, it also prevents starting engine in gear, so switch needs to be in Park or Neutral position to pass voltage to activate starter motor

 

So replacing the switch would be a good place to start? And if that doesn't do the trick to start poking at the wires to check if they are corroded or broken?
The only thing that gets me is that the lights used to work then they didn't then they did and now they don't. If it was the switch, wouldn't they just have died once and for all?

 

Putting the truck in reverse also makes a loud clunking noise and a lurch, could that also be part of this NSS?

 

A lurch and clunk would indicate something more is wrong. The NSS alone wouldn't be the culprit, but that being known could mean the NSS is one of the symptoms of a bigger problem.

To help you further, we need to know if the transmission is automatic or manual, as the two are very different.

 

Auto

 

Block tire(s)

Start engine
Set emergency brake
Put trans in Reverse
Turn off engine
Turn key on

Have some one watch reverse lights while you move shifter a little one way or the other, you could just have a loose shifter cable, very common issue on all Ford trucks with column shifter.

Google: ford column shifter problems


If that doesn't do it then get under the truck and wiggle the NSS switch and its wires, with someone watching reverse lights.

If that doesn't do it then pull out reverse light bulb.
Check for 12volts using FRAME as the ground, if it has 12volts then use Bulb Socket as the Ground, if no 12volts then socket Ground is bad, if should be on the frame rail, clean it.

 

a loud clunking noise is a sure sign that is something definately wrong inside your transmission

the reverse switch is probably worn out

it operates off of the negative voltage side , at least on the older vehicles

 

I got a current checker, took out the bulbs and checked the sockets. Nothing.
I took apart a connection about a foot down the wire, checked there. Nothing.
Cleaned the connection a little and put it back together. Lights now work.
I'm going to pick up some Di-Electric Grease and put it in the connection. And get this sucker inspected.

 

It might also be the shifter, because at first they worked, then i shifted to P then back to R and they didn't. The last 10 or so R-P-R shifts gave me working lights.

 

i would just purchase a brand new connector and solder it in

corrosion has already gotten under the wire insulation

 

^ X2

 

I'll look into that when I get to the store. Thank you everyone for your help, this thread has taught me more about this issue than Youtube lol :D

 

One last thing I'll just throw in.

Get the engine and everything all warm, put it in park and pop the hood. Grab the transmission dipstick and a white papertowel. Not a rag, but a white paper towel.

Using the dipstick, gather some fluid on the paper towel. It should look red/pink and not smell burnt. If it's red/pink and smells burnt, get the fluid changed or flushed. If the fluid is brown, or black, leave it be.

However, regardless of ANYTHING above, if you see ANY metallic specks in the fluid itself, DO NOT get the fluid changed or flushed, and here's why.

In this instance, the fluid has suspended clutch material inside it, which is allowing the transmission to engage and all that. If the fluid is changed, or flushed, all that clutch material goes away and you're left with a damaged/worn transmission that is likely to slip. Here's a video on the subject. Your pocketbook may just thank you, lol.

 

That's interesting, thank you for pointing that out. I will need to do an oil change in the next few days, I'll check the transmission fluid when I do that.