Headlights dimming

[thtniggey]

Hows it going everyone! Ive been having a reacurring problem after driving about 15 minutes at night my charging gauge will drop amd the headlights will get dim (high and low beam) what could be the cause of this? Bad alternator battery maybe? Any help is appreciated as usual!
1977 Ford F100 Ranger XLT 351M 4wd

 

[5.0Flareside]

May be bad alternator.. But I think it's more of a weak connection or poor wire conductivity..


Sent from my iPhone using Ford Power

 

[thtniggey]

Alrighty. I will check all the connections tomorrow! Its been doing it for some time now!

 

[DNFXDLI]

What Chris said....sounds like a bad connection....check everything.
You might want to read this guide....
It's for a 79 but the principles are the same.

http://www.fordtruckfanatics.com/forum/showthread.php?t=29167

 

[fatherdoug]

Might also be a voltage regulator. Also check the mounting screws for the regulator to the fender. If I remember right, the mounting screws are the ground for the regulator?

 

[BuzzGun79]

Check gounds as stated, but I Highly suspect the Voltage Regulator....unless the truck battery is going totally dead where you have to jump it..then Alternator...or both

Doug Nailed it,,,the regulator screws do ground the unit...

 

[G.O. Stang]

If you're still running the original regulator, it's worth it to just replace it with a newer electronic one.

 

[LEB Ben]

Voltage Regulator gets my vote too.

 

[m78]

Does the charge gauge go down during the day while the lights are not in use ?
Or only after the lights have been on for the 15 minutes ?

 

[thtniggey]

Only after the lights have been on for 15 minutes. During the day its fine

 

[chris989]

Regulator

I agree with the regulator. Try it first, they are inexpensive and easy to change.
The regulator on my Super duty did the same as you describe only it would would over charge. I replaced it, and a few years later it would go bad again.

Chris

 

[m78]

Thats a hard call. Works fine until under a load. And not much of a load. I'd have the alternator checked.
They do it for free at the auto parts around here. Have you checked the connections and grounds yet ?

 

[BuzzGun79]

^^^ not really Mark....Having been around these vehicles in my prime days...regulators were pretty common of failure on these trucks...and cars to..they are a failrly sensative unit..Up here climates extreme cold, dampness,excessive heat,humidity can also play a role in the life of the units as well

 

[thtniggey]

Im definetly leaning towards the regulator now. Is it located on the inner fender? Also we have had a very cold winter. Could this have played a role?

 

[fatherdoug]

It is on the inner fender, passenger side.

 

[BuzzGun79]

Im definetly leaning towards the regulator now. Is it located on the inner fender? Also we have had a very cold winter. Could this have played a role?

It is a possibility thniggey...I can recall an instance on my first ride 68 Ford,it was winter and cold,the car was fine giving no warning or any indication of failure or discharging even under loads...parked the car for the evening..next morning it was dead replaced the regulator,charged the battery and was good to go.....There were also similar occasions with some of our customers vehicles as well

 

[m78]

Getting a alternator tested is free