MG Car Repair: 68 light problems, purple trace, mgb car

Question
QUESTION: i have 68 mg the dash lights turn signals brake lights all quit working I have run wires i have also put power on them which makes everything but brake lights work but it makes tail lights stay on when key is on. Please let me know anything i can do to solve this, i have wiring diagrams but still not helpful.

ANSWER: Hi keith,

I can probably help with the tail lights and brake lights but I need to know what kind of MG it is. An MGB, MG Midget, MG Magnette, MG 1100 Sedan or MGC ?

Howard

---------- FOLLOW-UP ----------

QUESTION: it is a mgb car#ghd4h/152089 g commission#   004470n it is a gt

ANSWER: The tail lights and brake lights on the B-GT are separate circuits and the only place they are close to each other is at the rear bulb sockets. To isolate the problem in a smaller area just go to the back of the tail light assemblies on each side (inside the car) and disconnect the Green w/purple trace wires on each side and disconnect the red wires on both sides at the tail light assemblies. (be sure the wires don't make contact with any metal and turn on the parking lights and with a 12v test light check the red wires on the harness side. You should see power.
Then check the Green w/purple tracer wires and you should see no power. Then have someone turn on the ignition and step on the brake pedal and test the Green w/purple wires on both sides and you should see power. Be sure the lights are off and hold the brake and test the red sires and you should have no power.

This tests the car and the harness. If it checks as correct the problem is in the tail light assembly.

Nest is a test of the assembly. Turn on the key and have someone hold the brake peddle down and retest the green w/purple trace wire in the harness for power. If you have power touch the end of the green w/purple to the red wire on the tail light assembly and note if the park light came on and then touch the green w/purple lead from the tail light assembly and see if the brake light came on. If it did check the other side the same way.

That is a test of the assembly and bulbs and sockets.

Connect the wires on both sides back together and turn on the ignition and have someone step on the brake pedal and connect your clip of your test light on the bumper and with the prob of the test light while the brake pedal is depressed touch the prob to the metal part of the bulb socket on the back side and if you get a light you have a bad or disconnected ground wire. Test both sides.

That is a test of the ground circuit.

If you follow exactly as I outlined you will find where the problem is. If the problem was in the forward harness of the car then that requires further tests and let me know and I will tell you how to run those tests.

Let me know,

Howard

---------- FOLLOW-UP ----------

QUESTION: hello sorry to bother you again. i am gettin no power on the red wire. the other wire is keppin power with key on but i believe someone is got a constant hot on it so i gotta find that problem but if you could help me with this red wire and also green one i would greatly appreciate it. its gettin nerve rackin lol thank u again

Answer
The red wire gets it's power only with the lights turned on and from the light switch as does the same red wires to the front parking lights and all the instrument lights.

The green w/purple wire gets it's power from the brake light switch only when the brakes are applied. So do that test with a 12v test light at the brake light switch (key on) So test the Green w/purple at the brake light switch and if it is hot there disconnect the wire from the switch to see if the test light goes out. If you still have power to the green w/purple wire with it disconnected from the switch then you either have a wire plugged in the wrong socket somewhere in the harness or a short in the harness somewhere.

Test the red wire at the light switch with the lights on and if you have no power at the light switch and you do have power at the switch on the brown wire then the switch is bad.

You need a wiring diagram to trace and find any electrical problem. If you don't have a diagram let me know and I will put one up on my web site for you to copy. No one even the designer can trace electrical problems without a diagram.

Howard