Here’s the background: we have a 1986 Honda Civic wagon that gets driven, for the most part, once a week for a total of 12 miles roundtrip. The second half of that roundtrip is at night. I had noticed that ever since we got the car, the dashboard backlighting would come on whenever I stepped on the brake, which I thought was weird, but inconsequential.
The problem, which we didn’t discover until fairly recently, is that there is some hinkyness (technical term) with the tail light/brake light wiring. The brake lights are located in the same place as the tail lights, but the brakes are brighter. Or should be, anyway. What we’ve discovered is that when the headlights are turned on, the “tail lights” are on at full brightness. Meaning that there’s no discernable difference at night between having my foot on or off the brake pedal.
Some of my concern is about getting pulled over, of course, but I’m most worried about the safety issue this creates for me and for other drivers since a motorist behind me may not notice if I have to brake suddenly. Obviously, I need to get this taken care of.
I’m just wondering if anyone has any experience with this specific type of electrical problem, whether the brake/dashboard lighting effect is a red herring or is actually related, and what kind of costs I might be looking at with a mechanic. I have it in the back of my head from somewhere in my past that vehicle electrical problems can be difficult to diagnose as the source can be hard to find, making these types of repairs very expensive. Is there truth to this?
Any help, even of the anecdotal type, is appreciated.
The dashboard light is probably on the same circuit as the rear running lights. My 2001 Isuzu Rodeo had a problem where the fuse for the running lights burned out every time I stepped on the brakes when they were on. I wiggled a bunch of wires until it stopped doing that, although I still don’t know exactly what fixed it.
The display light still goes on and off at random on the radio.
It could be a weak or missing ground connection at one of your tail lights. Tail lights normally use a bulb with two filaments. One filament (finer wire, lower wattage) is the running lights, the other is the brake lights. (heavier wire, higher power) These two filiments share a ground connection. If that ground connection is weak or missing, then the brake light circuit can back-feed power to the running light circuit, which is also what supplies your instrument illumination.
Look for a broken wire, or a missing or corroded screw connecting a wire to the body metal.
Forgive me; I am mechanically uninclined. If that is the case, would that mean it’s something I can fix myself, or are you saying it could be a cheap fix at a real mechanic’s shop?
I edited my post while you were replying. See the bit I added at the end…I’d bet at least a six pack that this is the problem. Mechanics are notoriously bad at finding electrical problems…electronic techs often aren’t much better. If you show a mechanic what I wrote, and you see an “AHA!” expression, then there is a good chance they can find the problem. If all you see is “???” in thier eyes, move on.
You might be able to spot the problem yourself, it’s worth a look, be guided by Kevbo’s suggestions. I’ve also seen a bulb cause the problem when someone forces the wrong type bulb into a socket.
I’ll take a look when I get home. I don’t think there’s a forced bulb issue because I changed the bulbs myself a few months ago, but I’ll look for loose wiring. It would be fantastic if this was a simple fix.
Thanks, guys! All commentary still welcome, of course.
One possibility is that a dual-filament (combination brake/tail) bulb has been inserted into its socket 180’ off, which could connect the brake light circuit to the taillight/dash illumination circuit. These bulbs (typically # 1157) have two contact points on their base, and their alignment tabs are offset which usually - but not always - prevents their being installed backwards. I run across it now and then. It’s the simplest thing to check and rectify, and that’s where I’d start. Just make absolutley sure that the tabs match the slots they go into - there’s a shallow slot and a deep slot, with a corresponding high tab and low tab.
Electrical problems like this can be absolute rock-solid cast iron buggers to find, especially on a car that’s 21 years old, so there are probably no fewer than seven hundred locations where corrosion could have compromised a connection, or wires could have chafed.
The first place I’d look is at the brake light bulb sockets and the headlamp sockets as well. (Just for giggles, unplug both headlamps and see what the taillight/brakelight behavior is.)
From there, I’d think seriously of taping red cellophane to a flashlight, duct-taping the flashlight to your headrest, facing backwards, and turn on the light when you step on the brakes. Did I mention that electrical problems in old cars are horrible things to track down?
The good news, and most important news, is that the problem is completely fixed. Also, my wife, who is far more observant than I am, has reaffirmed one of the many reasons I would probably be huddling under newspaper on a street corner without her.
The bad news is that the problem was a result of multiple instances of user error. In the first place, one of the bulbs was completely the wrong bulb. I don’t know if that’s something that was done by a person who had the car before I did, or if I did it when I replaced multiple bulbs a few months ago. Either way, somebody screwed up. The bulb had only one filament, so there you go.
The second error was certainly my fault, in that one of the bulbs was in backwards (I think every single one of you called that). I don’t know which problem was more pressing, but no matter now. A five-minute trip to Autozone, the right bulbs in the correct way, and everything functions properly now. Including the dashboard-light-when-on-the-brake problem.
As an aside, the driver’s side tail lamp does have an odd grounding problem, and we (read: my wife) noticed that the other side had a newer assembly with a more proper grounding. However, the driver’s side ground wire was ground well enough to make steady contact, so that was not part of the problem.
Glad to hear you found the problem, and w/o a lot of expense. It’s satisfying to attempt something you know little about and succed in accomplishing it.
Did I mention that electrical problems in old cars are horrible things to track down?