Failed inspection

2000 Mercury Sable Wagon, auto transmission, 105,000 miles. Failed inspection because of an electrical problem as follows.

When brakes are pressed, right and left brake lights come on but not the top light.

When car is put into reverse, backup lights are very dim, but top brake light is on full brightness.

When car is put into reverse, and the brake pedal is depressed, dim backup lights and the top brake light go out. Left and Right brake lights come on.

I looked at the electrical diagram and the two systems are on different fuses. The top brake light and the backup lights do run through the same conduit into the lift gate. Should I look there for a short or a ground? Does anyone know how the wires run through the chasis?

I think you have a ground problem not a short. Usually, the ground for those lights is close to the light assembly. There may be one ground for both assy. or one for each on each side. Look around in there and you will see a wire fastened to a stud in the body. Remove the fastener and clean around the stud and the wire terminal with a wire brush preferably.

I don’t know the wiring system but usually(?) when lights are dim the fault is most times a poor ground connection or a bad bulb or socket.

You may want to check for continuity between the vehicle and the hatch via the ‘accordion’ wire protector. Attach the tester and wiggle the wires to look for a discrepancy.

The body to hatch wiring wears the same way as the wiring between the body and your side doors (usually the drivers door power goes first).

Thanks for the information, I will check for grounds tomorrow. If that is not the problem, I will come back looking for more help.

If it is the problem, stop back and let is know how it turned out.

have you ever had the rear lift gate replaced? or body work on the rear end or lift gate?

I have had the car for 4 years and have not replaced or worked on the lift gate. The light issue is a recent occurance.

There were no grounds close to the light assemblies. Started tracing the backup light wiring and found a broken wire in the flexible conduit to the lift hatch. Repaired it and all is well with the backup lights and the top stop light. Thanks for your help…

Thanks for taking the time to let us know how it turned out.