QuestionI have a 65 mustang that the headlights blow the fuse when the switch is pulled...where is a good place to start to trace the problem?
Answer
65Stang
You need a multimeter for this test.
- Turn the headlight switch off. Do not turn ON while doing this test or you will likely blow the meter fuse. If you disconnect the battery now that's even better.
- Disconnect both head light connectors (left and right lights).
- Set yourself up at the drivers floor board with the meter.
- Set the multimeter to test for continuity (ohms), preferably to "beep" mode so you don't have to watch the display.
- Connect one lead to a good ground.
- Try the other lead to a good ground at another location and get the beep to make sure you are good to go.
- Disconnect the high beam switch connector(foot switch).
- Run the following tests with the other lead, they should all be open (no beep). If any of them "beep" the problem is narrowed down as follows:
Red-Yellow: The feed circuit from the headlight switch is shorted.
Red-Black: The low beam circuit is shorted.
Green-Black: The high beam circuit is shorted.
If you find a short, it's a matter of tracing the appropriate colored wire looking for a frayed/shorted connection. However, you may be able to narrow down the location of the problem even further. There is another 8 pin connector between the foot switch and the lights, but I do not recall if it is under the dash or under the hood. Disconnect this and run the test again on the same colors on both side of this 8 pin connector. That should tell you which direction the short is, towards the head lights or towards the interior switches.
If you find no shorts with these tests, there is the possibility that the headlight switch itself may have an internal short. To test, disconnect the battery, turn it on, then run the test again from the foot switch on the Red-Yellow connection. Good luck.
