Questions and Answers

Mercury Tracer Lights On, OD Kicks Off Q. Hi, I have a strange problem that no one seems to be able to figure out. I'm hoping you can give me a good idea where to start to resolve it. I'm positive it has to be a wiring problem, but don't know where to start looking. I recently purchased a 1993 Mercury Tracer sedan, 4 cylinder, with automatic transaxle with overdrive for my daughter. The car has 93,000 miles on it.

The car runs great, until you turn on the headlights and parking lights. Here's what happens when you do. When driving in overdrive, if the headlights and parking lights are turned on, it down shifts into drive, and the rpms go up. It will not change back until the lights are turned off. It will stay in drive all the time even when stopped, and even pulls out in drive. It will not shift into low gear even when stopped.

Once the lights are off, everything returns to normal. It will go into low gear if manually shifted. Also, the temperature gauge on the dash doesn't work, until you turn the car off, then it reads the temperature. Strange?

I contacted the previous owner, whose name I found on a repair receipt in the glove box, who stated he had problems with the dash panel lights flickering at night when he would turn on the headlights, which it is still doing, and he had a new headlight switch installed at a Mercury dealer.

He stated this repair did not correct the problem. He also had a new alternator installed at the same time. He also mentioned that the rpms would significantly go up when the lights were turned on, but hadn't noticed it down shifting, I think he just didn't notice it, it took us a week before we noticed it downshifting.

When the repairs didn't correct the problem, he returned to the dealer who went over the car and stated they had no idea what was wrong with it, so he said he just stopped driving it after dark. By the way, he is the original owner and he said it came from the factory with these problems.

The headlight switch is located on the left side of the steering column and has a separate switch on the dash to dim and brighten the instrument panel lights. Any pointers to help us get going in the right direction would be greatly appreciated as my daughter will need this car very shortly, with the headlights in working order.

No one seems to know where to start or what the problem could be. The only thing I can determine is it must be an electrical problem, but have no idea where or what to start looking at.

Heck, if the dealers garage couldn't find what was wrong, and all the local mechanics have no idea what it could be, then I know I'm going to have problems without some very good advice. Hoping you can help me so my daughter doesn't have to drive to the community college with flashlights taped to her hood.

Thank you for your time, it is very much appreciated.
Valerie

A. I've been fixing cars, man and boy, for almost 40 years and I have never even heard of a problem like this. That's what I love about this business, just when you thought you've seen it all, something comes along to prove you wrong.

I have been studying wiring diagrams with the three technicians who work for me. We spent two days studying on it and the only thing we can come up with is there is a harness pinched somewhere. This opinion is based on the fact it came from the factory this way. I have seen harnesses get pinched between engines, transmissions, frames and bodies.

Another thing to try is get a wiring diagram for the headlights and parking lights. Unplug the headlight switch connector and apply power to each circuit, one at a time, until you find the circuit that is causing the problem. That would possibly, at least, narrow down the possibilities.

I wish I had a quick and easy answer for you, but I think this is going to require detaching the harnesses for their mounts and physically inspecting each one. There is a connector on the side of the transmission that you can unplug.

A car with this problem should never have been delivered to a customer who just purchased it and it should have been either repaired or bought back as a lemon.