headlight...from dim to bright - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Cheyenne71 · 05-18-2002, 03:08 AM

Can someone tell me why my headlights go from dim to bright when I step on the gas? Is there anything I can do about it?

Big69C20 Toy · 05-18-2002, 03:50 AM

Does it actually switch from low to high beams or is it just that the setting you have it on gets brighter? if it is switching low/high then i'm not too sure, but if it's just getting brighter on the same level then my thought is you have soem sort of a power drain, probably a bad ground somewhere and as the motor increases rpm the alt of course puts out more power and that makes up for the poor grounding. I could be wrong (and it has a good probability) but that's just my thoughts. Check your main grounds and such, see if you've got something loose. Good luck and others with more electrical knowledge will help i'm sure.

------------------
69 Custom 20, 396BB,Longbed fleetside.
New Oak Bed With SS strips.

Edelbrock performer RPM-O, Edelbrock 750Carb, Headers, HEI, 2 40" glasspacks.
Stereo: Classic-style tape deck/radio, 2 6x9 Cerwin Vega's in doors, 2 10" Neo subs under seats, 1 900 Watt amp.

SN= Ares220 on AIM.

Located in Beautiful Southern Cali or Michigan when i'm at school.

1ToBjimmyk5 · 05-18-2002, 05:27 AM

Sounds to me like to voltage reg. is bad.
If you have a volt meter, connect it to the bat. and see if the voltage goes up when you increace the RPM's (can also use test light, it will get brighter at higher RPM's)

Longhorn Man · 05-18-2002, 06:11 AM

That is normal.
The altinator is not able to put out many amps at an idle. It is designed to be a high rpm unit, and that is where it spends 90% of it's life, so the engineers make it so that they work better at speed than at idle.

------------------
'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite.
E-mail longhornmail@yahoo.com
My name is Andy...not Randy...I'm in Ohio...Not Illinois...close enough?
Columbus Ohio

*Zkast* · 05-18-2002, 09:32 AM

Sounds like a good time for a 10si unit (73-86 alternator) Bolts into the same bracket assembly and only requires 3 wire modification. This will give you a solid 13.8-14.5v or higher at idle where your old one would only do 12.8 at best. Amperage will also rise.

------------------
Pictures and more...
Email me
'71 LWB
350/350T, PS/PB
Special options? Yes, RUST... Need some?

Garrett
Olathe, Kansas

[This message has been edited by Zkast (edited May 18, 2002).]

Longhorn Man · 05-18-2002, 09:18 PM

But your lights will still dim at an idle.

------------------
'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite.
E-mail longhornmail@yahoo.com
My name is Andy...not Randy...I'm in Ohio...Not Illinois...close enough?
Columbus Ohio

*Zkast* · 05-18-2002, 11:29 PM

With a 10si(internal regulator 3 wire) it will produce 13.8 minimal and up to 14.5 or so while at 2000 rpm. That much of a voltage variance wont give you the fluctuation compared to 12.8 to 14.5

I guess they just didnt have the technology back then I dont know. I hated the dimming headlights at idle problem expecially when you have wipers/fan and lights on, So while at work one day I decided to throw the newer style on.
Problem solved

------------------
Pictures and more...
mailto:piston@zkast.com
'71 LWB
350/350T, PS/PB
Special options? Yes, RUST... Need some?

Garrett - Olathe, Kansas

05-18-2002, 03:08 AM	#1
Cheyenne71 Registered User Join Date: May 2002 Location: Spokane WA. Posts: 34	headlight...from dim to bright Can someone tell me why my headlights go from dim to bright when I step on the gas? Is there anything I can do about it?

05-18-2002, 03:50 AM	#2
Big69C20 Toy Livin' it up. Join Date: Nov 2001 Location: Richland, MI Posts: 2,212	Does it actually switch from low to high beams or is it just that the setting you have it on gets brighter? if it is switching low/high then i'm not too sure, but if it's just getting brighter on the same level then my thought is you have soem sort of a power drain, probably a bad ground somewhere and as the motor increases rpm the alt of course puts out more power and that makes up for the poor grounding. I could be wrong (and it has a good probability) but that's just my thoughts. Check your main grounds and such, see if you've got something loose. Good luck and others with more electrical knowledge will help i'm sure. ------------------ 69 Custom 20, 396BB,Longbed fleetside. New Oak Bed With SS strips. Edelbrock performer RPM-O, Edelbrock 750Carb, Headers, HEI, 2 40" glasspacks. Stereo: Classic-style tape deck/radio, 2 6x9 Cerwin Vega's in doors, 2 10" Neo subs under seats, 1 900 Watt amp. SN= Ares220 on AIM. Located in Beautiful Southern Cali or Michigan when i'm at school. __________________ -Greg; Sold the 69 C20. It's off to a better home with more love! Now onto the 86 CUCV M1009; K5 blazer with 6.2L diesel, corp 10 bolt axles, Detroit locker in the rear, trutrac front, 3.73 gears, 35" tires.

05-18-2002, 05:27 AM	#3
1ToBjimmyk5 Registered User Join Date: Apr 2002 Location: Centreville,VA & Millsboro, DE Posts: 47	Sounds to me like to voltage reg. is bad. If you have a volt meter, connect it to the bat. and see if the voltage goes up when you increace the RPM's (can also use test light, it will get brighter at higher RPM's) __________________ 1971 Chevy Blazer(looks like Jimmy),1988 Ford E350 Van,2001 Nissan Sentra(Wife), 1993 Nissan Sentra (to/from work),1985 Dixie (boat) with a big Johnson,And I want my 1970 Buick Conv. back!!!! Centreville,VA

05-18-2002, 06:11 AM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	That is normal. The altinator is not able to put out many amps at an idle. It is designed to be a high rpm unit, and that is where it spends 90% of it's life, so the engineers make it so that they work better at speed than at idle. ------------------ '69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it. FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite. E-mail longhornmail@yahoo.com My name is Andy...not Randy...I'm in Ohio...Not Illinois...close enough? Columbus Ohio

05-18-2002, 09:32 AM	#5
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	Sounds like a good time for a 10si unit (73-86 alternator) Bolts into the same bracket assembly and only requires 3 wire modification. This will give you a solid 13.8-14.5v or higher at idle where your old one would only do 12.8 at best. Amperage will also rise. ------------------ Pictures and more... Email me '71 LWB 350/350T, PS/PB Special options? Yes, RUST... Need some? Garrett Olathe, Kansas [This message has been edited by Zkast (edited May 18, 2002).]

05-18-2002, 09:18 PM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	But your lights will still dim at an idle. ------------------ '69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it. FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite. E-mail longhornmail@yahoo.com My name is Andy...not Randy...I'm in Ohio...Not Illinois...close enough? Columbus Ohio

05-18-2002, 11:29 PM	#7
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	With a 10si(internal regulator 3 wire) it will produce 13.8 minimal and up to 14.5 or so while at 2000 rpm. That much of a voltage variance wont give you the fluctuation compared to 12.8 to 14.5 I guess they just didnt have the technology back then I dont know. I hated the dimming headlights at idle problem expecially when you have wipers/fan and lights on, So while at work one day I decided to throw the newer style on. Problem solved ------------------ Pictures and more... mailto:piston@zkast.com '71 LWB 350/350T, PS/PB Special options? Yes, RUST... Need some? Garrett - Olathe, Kansas



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