Have a 1997 Mercury Villager van (same as a Nissan Quest) bought new, only 65K miles, everything runs great.
When I got it, had an alarm/remote door opener system installed. Just recently, whenever I hit the brakes, not only the break lights, but also the front side lights and the instrument panel lights come on.
Also, when using cruise control, if I turn on the parking lights or headlights, the cruise control goes off, and won’t come back on until shut off lights.
The alarm installer went out of business, so no help there (it may not be the alarm, but some chance it is). The alarm has two wires from the positive battery terminal and each has an inline fuse. I tried taking these out one by one, but all that does is stop the alarm arming and stops the remote door opener from working. No hlelp with the brake/lights problem.
During a very recent service, did have the break fluid replaced, as it was dirty. Any chance they did something that caused this?
I also thought if the break light switch was hinky, that might cause the cruise control thing, but not sure that makes sense, as why would it turn on the front side lights?
A big fat ceegar to the first one to solve this. Or pie.
BRAKE lights. In this case your brake lights are broken.
Have you had any body work done to the car? Do you live in an area where they use salt on the roads in the winter? The symptoms you describe are a classic case of a bad ground circuit in the brake light circuit. The brake lights don’t have a good ground so the current flows backward though the circuit looking for a ground. It finds a ground though the side lights and the instrument lights.
The feedback is preventing the cruise from getting a good ground.
BRAKE and no.
Does not sound like a brake light switch to me.
Here is what you do, tonight when it is dark, have someone step on the brake pedal (engine running) while you observe the lights from a distance. (20 feet or so) Are they both bright? One dim, one bright? Or both dim? If you are not sure if they are both bright or not, check another car. At the same distance they should be the same brightness. Also don’t forget the 3rd brake light.
If one light is dim, that is the side with the problem. You will need to access the back of the light assembly and find the ground wire (connected to all the lamps) and follow it to where it attaches to the body of the car. Either the bolt is missing / loose, the connection is corroded, or the wire itself is bad. Fix it. you want a clean tight ground connection.
If both lights are dim, look for either a common connector on the ground side, or two loose bad ground wires.
If I had a wiring diagram for your car, I could probably point out the location of the problem from looking at the diagram. But I don’t so I can’t.
Rick nailed it in one. I had a similar problem with my 2001 Saturn, which I first noticed as cruise control inoperative when parking lights/headlights on. My dealership didn’t have a Rick on staff, so they mostly scratched their heads and grunted.
Within a week or so I found that I only had one operating brake light. When I went to replace the bulbs, I discovered that the ingenious piece of crap that Saturn had engineered into the taillight assembly had failed. This was some type of “circuit board” arrangement made of thin galvanized steel. The wiring harness attached to this and then each bulb had a special socket that only made contact with the appropriate channel in the sheet metal. Apparently galvanized steel isn’t the best conductor, because under my brake light contact it had been completely arced to a powder. After I fixed that problem, my cruise control was operational again.
The same thing happened to the other brake light, but as I was contemplating a similar repair, Saturn issued a recall on the assembly and repaired both of them.
Thanks Rick for coming up with the answer. There is very little call for salting the roads out here in the Arizona desert, though.
Last night I checked the 3 brake lights, and all are as bright as usual, and equally bright, so I expect the bad ground connection is somewhere else. I still think it is in the complicated alarm system wiring. I pulled both fuses in that, and although still have the light-up problem, the cruise control works OK.
I opened the tail light lenses anyway, but no problems there I can see, so am taking it to a garage. At least now I know where to point the mechanic, and will insist he drag out a wiring diagram.
