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Is my light switch damaged? Headlights work, Tailights don't

Hello everyone. When I turn on my light switch, the headlights turn on and brake lights work, however the taillights don’t automatically come on as well as the lights around my radio, AC, and the letters next to the shift lever.

The mechanic said that the light switch needs to be replaced because of the wiring system being potentially damaged. Before I proceed, I wanted to ask the community first. What should I do?

I have owned cars where the panel lights and the tail lights were on the same circuit and protected by the same fuse. I often wonder if this was done as a safety precaution to let the driver know that the tail lights weren’t functioning. At any rate, I would check for a burned out fuse before replacing the switch. It might be wise to take the car to a shop that specializes in electrical work and have them check this out.

Yes, and I’d replace that fuse with a known good one, just in case the break is hard to see.

Another idea, you didn’t spec the age of your car, but on newer cars sometimes there’s an ambient light sensor involved, which can malfunction. If it thinks it is bright daylight it won’t turn those other lights on. If so it may be possible to over-ride this sensor fault by setting the lighting system up to full manual operation. Just pushing some buttons in other words. Check your owner’s manual to see if that’s possible. Worth a try anyway.

Long ago I learned that comparing electric current to water under pressure made it possible to intuitively consider the possibilities in diagnosing a failure. Of course a water leak is more visible than a current leak but electric current isn’t a spiritual enigma. And a VOM and test light will put a bell on the cat, so to speak.

I strongly suggest getting a good test light like this

to anyone trying to solve an electical problem on an automobile. For those who have the patience and determination to learn how to use it the results will be amazing. For others, take the car to a good shop.

Rod, that gizmo strikes me as being much less useful than a cheap DVM. First you have to plug it into a woking cig lighter socket. And on some cars the engine has to be running for that to have power. A DVM runs on it’s own internal battery, much more useful.

“White = Proper Connection to Source” ? what in the world does this mean, if anything?

And I distrust anything whose major feature is a “ergonomic grip design”,

I took a chance and bought one many years ago when the price was $ignificant and quickly wondered how I had ever done without it. It makes noid lights obsolete. It enables fully testing a relay pin by pin. I own several now. One with a 12 foot lead. I rarely pick up a VOM.

Like others have already mentioned, the trouble you are having with the running lights and other dash lights is most likely due to a blown fuse for the dash lights rather than the switch itself. The headlights use a different fuse than the dash/running headlights use so they work while the others can’t due to the bad fuse.

Often, the headlight switch has an automatic reset circuit breaker for the headlight circuit while the tail lights-running lights-parking lights are on a fuse.

Curious about “noid lights”. That’s a shortened name for “solenoid test-light”, right? Is a “noid light” different from an ordinary test light? You know, the kind with two leads, one you connect to ground, then probe w/the other. When you touch something with the probe that is +12 volts, it lights? So if you probed it to the fuel injector electrical input it would turn the light on and off rapidly when the engine was running.

Are you sure the headlights are actually working, and not just the Daytime Running Lights?

Your switch very well could be bad, and you could be chasing your tail if you think the headlights are working and they are not.


With the engine running and the digital test light on the control side of the injector circuit the light will quickly switch from red to green.

Wouldn’t an ordinary test light do the same thing? Except switching rapidly on/ off instead of red/green? Or wouldn’t that work with a fuel injector b/c it is switching too fast?