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  • 1965 - 1973 Classic Mustangs -General/Talk-
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Halogen Headlights

  • Thread starter Thread starter candphall
  • Start date Start date Jul 3, 2013

candphall

Active Member
Jun 8, 2009
488
32
49
Orlando Florida
Jul 3, 2013
#1
  • 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.
 

66Coupe289POWER

Member
Jun 4, 2007
81
3
9
Raleigh, NC
Jul 3, 2013
#2
  • Jul 3, 2013
  • #2

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.
 

tx65coupe

Active Member
Nov 29, 1999
1,551
1
37
Jul 3, 2013
#3
  • Jul 3, 2013
  • #3
It would be helpful to have all the info in one thread instead of making a new thread each time.
 

candphall

Active Member
Jun 8, 2009
488
32
49
Orlando Florida
Jul 4, 2013
#4
  • Jul 4, 2013
  • #4
Thanks. And no more new threads, got it
 
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