headlights flickering and turn signal issues killing all gauges - Ford Mustang Forum
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post #1 of 6 (permalink) Old 09-06-2019 Thread Starter
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headlights flickering and turn signal issues killing all gauges

I need help with a couple of issues related to my 1966 289 mustang
  • Whenthe car worms up my headlights start flickering
  • Recently,it got worst. When I turn my turnsignal (either way) the gauges in theinstrument cluster stop working,everything goes dead (oil, gas, temp gauges and speedometer; also the wiper switch). After a few minutes, theygo back to live as long as I donít try using the turn signals again.
    I consulted with Ivy66GT,he mentioned that the turn signals sharenothing in common with the instruments except they both use 12V power andexplained that the flickering headlights would normally be casued by a voltageregulator or alternator problem.
    Does somebody experience the sameissues?

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post #2 of 6 (permalink) Old 09-06-2019
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Even stranger, I just noticed you said your turn signals caused the speedometer to quit working. The speedo in these cars was strictly mechanical and would work at any time even coasting down hill with the engine turned off. The only electrical part of the speedo was the instrument panel lights which allow you to read it at night.

If yours is re-wired with an entirely different instrument panel then none of us can guess what was changed or what might be wrong with it.

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post #3 of 6 (permalink) Old 09-13-2019
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Had a weird issue like this once. Turned out to be the external voltage regulator. Corrosion internally from water intrusion.
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post #4 of 6 (permalink) Old 4 Weeks Ago
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I'd start by isolating the high amperage headlamp circuit from the dash switch by using a pair of relays. Use the dash switch leads as a trigger and power the relays with fuses powered right off the battery. Remember that the floor dimmer switch is part of this circuit.

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post #5 of 6 (permalink) Old 3 Weeks Ago
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The original headlight switch was rated and designed for 35 watt headlight bulbs and standard 7 was bulbs in the parking and running lamps. It wasn't uncommon back in the day for even the moderately more effective 55 watt "high intensity " lamps to cause the headlamp switch to flicker. Using a standard really wired to the head light circuits is relatively cheap and effective.
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post #6 of 6 (permalink) Old 3 Weeks Ago
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I have the original, factory FoMoCo headlights that came in our Mar '66 coupe. At 13V on high beam they are 45 Watt headlights NOT 35W. They are nearly 40 Watts on low beam. Anything can be defective even from the factory. But if you have a good, original headlight switch it will have no problem using 60 W headlights. I have done it and presented the data here 6 years ago. In my decades of Mustang ownership headlight flicker is almost always a regulator and/or alternator problem.

The OP hasn't even been back to AFM in a week so I think we may be talking to each other instead of answering the original question. I more than beat the subject of headlight wattage to death in this 2013 thread. Relays will cause as many, or more problems than they solve.

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