Reverse lights are not working?

For the benefit of others researching this problem, please allow me to start with the normal order of diagnostic steps, even though you replaced parts already. The most common cause of no back-up lights is the neutral safety switch. A real fast way to verify that is to turn the ignition switch to "run", then crawl underneath, unplug the neutral safety switch, then jump the two outer terminals in the connector with a stretched-out cotter pin or paper clip. If it's relatively dark down there, watch closely for a tiny spark when you do that. If you see that, it proves current is flowing, then you know at least one of the back-up lights is working. Of course, you can look at the lights to see if they're on. If they are, you know the fuse and every other part of the circuit has to be working, and the switch must be replaced.

Most people would start by checking fuse # 7 in the Junction Block, but that circuit and fuse actually feeds a number of other circuits not shown in these drawings. If the fuse was blown, you'd have other symptoms. It's designed that way because you would never know if the back-up lights weren't working, but you will notice other things are dead when that fuse is blown.

If jumping the two terminals in the neutral safety switch connector did not turn the back-up lights on, check for 12 volts on both of those terminals. There should only be 12 volts on terminal # 1 corresponding to the brown / light green wire, but rather than trying to figure out which one is the 12-volt feed wire, it's faster to just check them both. If that 12 volts is missing, we have to look between the fuse box and that terminal for a break in the wire. If you do have 12 volts, the break is after terminal # 3, the violet / black wire. There is a splice, S316 in that circuit. Those are always good places to find corrosion, although usually one back-up light would still work.

Very often in this type of circuit, a digital voltmeter can give misleading readings. That won't happen if all of the readings are taken while everything is plugged like normal, but then you'd have to take readings at the neutral safety switch by cutting the wires' insulation. That is never acceptable. Instead, you are more likely to get valid readings by using a test light instead. It has to be the older, inexpensive type with an incandescent light bulb inside, not one of the newer ones with LEDs. Here's links to articles that show how to use both of them:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

https://www.2carpros.com/articles/how-to-use-a-voltmeter

The article shows them using an auto-ranging meter. That's an expensive option that most meters don't have. If you need help setting up a regular voltmeter, I can help with that. Harbor Freight Tools has a perfectly fine voltmeter for around $8.00, and a test light for $4.00. You can find both at Walmart or any hardware store or auto parts store too.

Let me know what you find up to this point, then we'll figure out where to go next.

Wonderful. I'm here almost every day, but don't panic if at times it takes me two days to reply. This should be fairly easy to figure out.

For another clue, check if the license plate lamps are working.

I'm in northern Wisconsin, but I went through Dallas about ten years ago with a friend. He bought a paint booth from a fellow who bought a second body shop and combined them. Very friendly bunch of fellows to work with.

By "T-tap", I'm guessing you're referring to a Scotch-Lok connector. I have no use for them and never use them. They're fast and easy to slide wires into, but they don't seal out moisture. Electrical tape should also not be used on cars and trucks. It will unravel into a gooey mess on a hot day. The preferred method is to strip a half inch of insulation from the truck's wire, wrap the beeper's wire around it, solder the joint, then seal it with moisture-proof heat-shrink tubing. The problem is you'd have to cut the truck's wire to slide the tubing on, then splice all three wires together. The better approach would be to go right to one of the back-up bulb sockets, do the splice there without cutting the truck's wire, then seal it in a small blob of silicone gasket sealer. You can reassemble the lamp housing right away without waiting for the sealant to cure, but when it does in an hour or two, it will seal out moisture.

Those Scotch-Lok connectors get used quite often when people add on a trailer wiring harness. Corrosion sets up where the insulation was pierced, then pretty soon there's intermittent or no brake lights or taillights. What's worse, the small area of corrosion can't just be cut out and the wires spliced back together. Long before the wire corrodes apart, moisture will wick along the copper strands a long way, starting much of that wire corroding. As you strip the insulation back, you'll see the wire is dull brown instead of shiny copper color. Solder will not adhere to that brown wire. It's not uncommon to have to cut off three or four feet of wire in each direction from the pierced insulation before you can find good clean copper to solder to.

I sell LED lights at the nation's second largest old car show swap meet at Iola, WI every year. They do not require a ballast or any other modification on older vehicles. Hight intensity discharge, (HID) bulbs do, but that would be serious overkill for back-up lights. Where people run into problems on newer vehicles is the lights are run by a computer module that detects when a bulb is burned out and displays a message to that effect. LED bulbs don't draw enough current, so the computer thinks the bulb is burned out. For those, you have to add a resistor in parallel with the bulb to draw some additional current. That keeps the computer happy. A standard 3157 brake light filament draws very close to one amp. Back-up lamps draw closer to 3/4 amp. The LED replacement will draw just a fraction of that, so you have to add a resistor to increase overall current flow. Ohm's Law says "resistance equals voltage divided by current. We have 12 volts; we want roughly a half amp of current to flow through the resistor, so it needs to be, 12 / 0.5 = 24 ohms.

The next part of Ohm's Law says Power (watts) equals volts times amps, so, 12 x 0.5 = 6 watts. A somewhat standard value is a ten watt resistor. Those are big enough to dissipate the heat they will develop. You need a 24 ohm 10 watt resistor if your vehicle gives you a "bulb out" warning message.

The other thing to be aware of is how the individual LEDs are placed on the bulb. I have some bulbs that just shine straight back and not at all to the sides. The most popular ones have LEDs all the way around, so they shine in every direction. Those are better for taillights that sit inside a rounded red lens assembly, especially when that lens is meant to be seen from the side.

I don't have a shop. I used to be a tv / VCR repairman, then a suspension and alignment, electrical, and brake system specialist at a very nice family-owned Chrysler dealership. I saw customers bringing in radios to be sent out for repair, and pointed out I could do that for my parts department people. Eventually, by word of mouth between parts department managers, I was repairing for two dozen new and used car dealers around Wisconsin. Cost the dealerships a real lot less than sending them in. The customers paid a lot less, the parts departments made more profit, and I made a few bucks. Now I sell and repair radios at the Iola Old Car Show swap meet every year, the week after July 4th, but it's the LED light bulbs that pay my expenses. No one even looks at my car parts or service manuals. Every year I have a bunch of regular customers waiting with broken radios under their arms when I pull in.

For the bulbs, you can find them at Walmart or any hardware or auto parts store, but if you want a really good deal, look for the style you want on eBay. Do a search for "1156 LED".
Click on "put that item in your "Watchlist". Then, in your Watch List, click on "View other items like it. If you look long enough, you'll find them on an auction, often starting at $0.01 with free shipping. They'll almost always come from China, although a lot come from two addresses in the U.S, even though China is listed in the auction. If you buy enough of these, you're going to run into failures, either completely dead or with a few dead or flickering LEDs, but the same can happen with the expensive bulbs from the auto parts stores. For the price, you can buy ten in one auction and still save money. It can be hard to tell from the photos, but if you can touch or feel the individual LEDs, you're more likely to get one with a defect. Those with a glass or resin coating cost more but seem to be of a higher quality. The coating amplifies the light too.

Hi,

Thank you for the update. We like to know how things turn out.

Please feel free to come back anytime in the future. You are always welcome.

Take care,

Joe