The Ford Barn

REByar · 02-21-2015, 11:18 PM

Hi All,

I just installed an additional drum style brake light on the right side. The running lights work, the brake lights both work. But when I am driving at night and I put on the brakes the front lights dim. Just for a second or two and then they brighten back up. Is this a ground issue? When I just had the original brake light on the left this did not happen. Just started with the additional new one. I use an alternator and the system is still 6 volt.

Any assistance would be greatly appreciated.

REB
August 28 Tudor

Tom Wesenberg · 02-21-2015, 11:29 PM

You've doubled the brake light drain, and it's taking the alternator a split second to adjust to the load. It probably also happened with the single light, but to a much lesser degree. If the power wire for the lights was right at the battery instead of at the alternator output, you probably wouldn't notice this, but I wouldn't worry about it. Actually the brief flicker of headlights might be a good thing by making other drivers more aware of you.

daveymc29 · 02-21-2015, 11:40 PM

I don't have the flicker, but on my roadster with an Optima battery I show very little charge on the amp meter after running just a half mile to a mile. With my coupe with a lead acid regular battery I see about 8 to 10 amps charge most of the time, even after a several miles drive. Both cars have 6V, Poss. ground alternators. The only real difference is the two batteries. Any clues? Both seem to start, and drive at night with lights, just fine.

J Franklin · 02-21-2015, 11:58 PM

Compromised battery comes to mind.

Tom Wesenberg · 02-22-2015, 12:05 AM

Quote:

Originally Posted by J Franklin

Compromised battery comes to mind.

I agree that the weaker the battery, the more you will see the flicker. If you look at the ammeter with the engine running about 800 RPM, then turn the lights on you should also see the needle drop below 0 for just a split second, then return to the normal range.

SeaSlugs · 02-22-2015, 02:33 AM

Sponsored Links (Register now to hide all advertisements)

my "modern" chevette does this when i stop with the highbeams on at idle, press brakes and headlights dim...alternators like generators can only create so much juice at a certian RPM and at such a low idle like the model A it may not be turning the alternator quick enough to keep up.

02-21-2015, 11:18 PM	#1
REByar Member Join Date: Mar 2013 Location: Ft.Mill, south carolina Posts: 52	Headlights dim when push the brake pedal Hi All, I just installed an additional drum style brake light on the right side. The running lights work, the brake lights both work. But when I am driving at night and I put on the brakes the front lights dim. Just for a second or two and then they brighten back up. Is this a ground issue? When I just had the original brake light on the left this did not happen. Just started with the additional new one. I use an alternator and the system is still 6 volt. Any assistance would be greatly appreciated. REB August 28 Tudor

02-21-2015, 11:29 PM	#2
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Headlights dim when push the brake pedal You've doubled the brake light drain, and it's taking the alternator a split second to adjust to the load. It probably also happened with the single light, but to a much lesser degree. If the power wire for the lights was right at the battery instead of at the alternator output, you probably wouldn't notice this, but I wouldn't worry about it. Actually the brief flicker of headlights might be a good thing by making other drivers more aware of you.

02-21-2015, 11:40 PM	#3
daveymc29 Senior Member Join Date: Sep 2010 Location: Danville, CA Posts: 1,554	Re: Headlights dim when push the brake pedal I don't have the flicker, but on my roadster with an Optima battery I show very little charge on the amp meter after running just a half mile to a mile. With my coupe with a lead acid regular battery I see about 8 to 10 amps charge most of the time, even after a several miles drive. Both cars have 6V, Poss. ground alternators. The only real difference is the two batteries. Any clues? Both seem to start, and drive at night with lights, just fine.

02-21-2015, 11:58 PM	#4
J Franklin Senior Member Join Date: May 2010 Location: Oregon Posts: 5,963	Re: Headlights dim when push the brake pedal Compromised battery comes to mind.

02-22-2015, 02:33 AM	#6
SeaSlugs Senior Member Join Date: May 2010 Location: Central, IL Posts: 3,968	Re: Headlights dim when push the brake pedal Sponsored Links (Register now to hide all advertisements) my "modern" chevette does this when i stop with the highbeams on at idle, press brakes and headlights dim...alternators like generators can only create so much juice at a certian RPM and at such a low idle like the model A it may not be turning the alternator quick enough to keep up. __________________ 1929 Model AA - Need long splash aprons!