I have an 89 5.0 and my headlights flicker. also the voltage gauge goes up and down and the dashlights flicker and I can heard the fuel pump sound flickering up and down. what could be causing this. i would really appreciate any help. im kinda worried that it could be like a short or something.
Why are my headlights flickering on my 89?
- Thread starter JesseR
- Start date
-
Sponsors (?)
Mavrick
Founding Member
Sounds like the alternator is dying, or overcharging. Either way needs to be replaced.
Check the voltage at the battery whith the car running, see if it's over charging.
Check the voltage at the battery whith the car running, see if it's over charging.
- Apr 9, 2002
- 1,635
- 18
- 59
Thats a mustang defect..happend to me on my 88 t-top but I never fixed it, sold the car like that! Anyways I dont think anyone has ever pinpointed the problem. My 92 doesnt do it at all so I guess ford fixed the problem in the early 90's. Good luck! 
the headlight wire from the headlight to the multi function switch is barely adequate (esp if you have a GT with fog lights). install a relay on the fog lights at a minimum, (esp if you have this problem mostly when the fogs are on).
i would also hit the local parts store - most do free charging system checking for you. makes it easier to troubleshoot your system.
or if you know your battery voltage at rest (should be ~12.2- 12.6 volts) and the alt should put out close to 15 volts at anything above idle (depends upon pulleys, etc). just rough guidelines.
good luck.
i would also hit the local parts store - most do free charging system checking for you. makes it easier to troubleshoot your system.
or if you know your battery voltage at rest (should be ~12.2- 12.6 volts) and the alt should put out close to 15 volts at anything above idle (depends upon pulleys, etc). just rough guidelines.
good luck.
1986LX2002
Founding Member
- Aug 15, 2002
- 317
- 0
- 0
rd
Founding Member
Absolutely check the headlight wire size and fix the foglights, as that is a known Ford problem, with a well documented fix.
Make sure the ground circuits and connections are good.
Then, you may want to replace the headlight switch. It has a circuit breaker, and if it has been subject to any of the above problems and has been opening and closing, it needs replacing. Sometimes, the circuit breaker itself causes this problem by just getting weak and failing.
Last thing is the voltage regulator, as it will cause this while it is in the process of failure.
Make sure the ground circuits and connections are good.
Then, you may want to replace the headlight switch. It has a circuit breaker, and if it has been subject to any of the above problems and has been opening and closing, it needs replacing. Sometimes, the circuit breaker itself causes this problem by just getting weak and failing.
Last thing is the voltage regulator, as it will cause this while it is in the process of failure.
houstonstangguy
Founding Member
both of my 89's did that too, and both were the actual headlight switch to the left of the cluster. pop it out and i bet when you unplug it you will see that it is a little burned up and shorted out. that little plug switch cluster for fog lights and headlight is only like 17.00 but it has been a few years since I got one. Id be willing to bet it is something simple like that. thats exactly what it was on both of mine. it is a quick and easy check, so i would do that before doing the other stuff mentioned.
if it isn't that, then I agree with the alt. or relay scenarios....
good luck
if it isn't that, then I agree with the alt. or relay scenarios....
good luck
Similar threads
