When you have some light operation but it is not correct, that is almost always due to a bad ground. To verify this, if you find, for example, the left tail light is dim, remove the right tail light bulb and you will see the left one go out completely.
As an alternative, you can measure the voltages on a rear socket. Most sockets have three wires. One will have twelve volts when the brake lights are on. A second wire will have twelve volts when the tail lights are on. The third wire is the ground. That one must never have any voltage on it. If that wire has a break in it, you will typically find around four to six volts on it when either light is turned on. If you do, follow that ground wire to find where it is broken.
The two most common causes of a bad ground are the wire is rusted off where it bolts to the body, (one wire on each side of the car), and someone installed a trailer wiring harness with Scotch-Lok connectors that do not seal out moisture. Problems develop once the exposed wire corrodes away.
Tuesday, May 23rd, 2017 AT 5:49 PM