Halogen Headlights

Discussion in 'Classic Mustang Specific Tech' started by candphall, Jul 3, 2013.

  1. This is what I found , the car has been totally rewired , the voltage out of the headlight harness is 12.30 volts. When I plug in the headlight extensions the voltage drops to 11.58 volts at the bulbs. I am attributing the voltage drop to old extensions which I have not replaced. Hence the dim lights. Am I thinking correctly. I would like a second opinion before replacing the extensions. The only thing I find odd is the voltage a drop is identical on both sides.
  2. effc931d-1501-4c5a-8e71-6bfdbc515f20_zps92ed3aef.jpg
    Please forgive my crude diagram, paint is not my strong point. This is a overly simplified diagram of the headlights. All voltage drop readings need to be done with the headlights on. First measure voltage from point A to point J to check the ground side. You want as close to 0v as possible and anything over 0.5v is not good. If you have a lot of drop, isolate where by measuring from point A to point K, point J to point L, and point K to point L. Clean connectors, replace loose connections, solder twisted wires, or whatever else you need to do to repair the circuit. Next when the ground is good measure from point B to point C, point C to point D, so on and so forth until you have checked every leg of the circuit and repair as needed. If there is drop between C and D or E,F,and H then that switch is worn out. Remember this is a series circuit and anything that has resistance will use some voltage and that reduces the voltage to the lights.
  3. It would be helpful to have all the info in one thread instead of making a new thread each time.
  4. Thanks. And no more new threads, got it