The Ford Barn

Ken/SC · 05-19-2015, 07:04 PM

I have been having problems with Direct Replacement Halogen Headlight Bulbs. I had a bulb go bad, I bought a new one from one of the A vendors and it was dim. It only burns one element. When I try my old bulb from the other headlight of the car in the same socket it works fine.

The only difference I see in the bulbs is the shape of the contacts on the bottom. On my old one the contacts are football shaped. On the new vendor bulb they are round. The vendor sent me another one, it is dim in both headlights also. They want to say its a ground problem. But my old bulb works fine in both sockets.

I wish I could remember where I bought my original halogen bulbs.

Does anybody have an idea what the difference is in the contacts?

Ron/IA · 05-19-2015, 08:39 PM

If you could provide a photo of the bulb's bases; that would give the Fordbarn population more to work with.

MikeK · 05-20-2015, 01:23 AM

The problem is with your sockets, not the bulbs. The two brass socket contacts with springs under them become worn in their holes on original sockets. This allows them to be cocked sideways shorting to each other and/or the shell when the bayonet bulb is twisted in.

The bulbs with football shaped contacts (BAY15B bases as opposed to BA15B) have a gentler ramp and are more forgiving to the socket contact side-play. The newer round bulb contacts(BA15B) tend to hang up on the two brass contacts and will twist them against the shell if they are loose in their holes through the fiber insulator at the socket base.

Football contacts

Round contacts

To compound the problem, most of the reproduction sockets have larger contact heads and thinner, sloppier fit fiber bases that permit off-axis contact movement and thus will short easily.

Applying a liberal amount of dielectric grease helps, and in this case it does more than act as a corrosion inhibitor. It acts as a lube. Make sure it gets under the socket contact rivets to lube them through the fiber base as well as on the bulb base contacts to prevent the lead solder from dragging the socket rivet contacts sideways when you twist the bayonet into its lock.

BILL WILLIAMSON · 05-20-2015, 05:00 PM

Sponsored Links (Register now to hide all advertisements)

GREAT POST, Mike K,
Sometimes a simple "trick" can save a lots of frustrating headaches & needless expense!
Bill W.

05-19-2015, 07:04 PM	#1
Ken/SC Member Join Date: May 2010 Location: South Carolina Posts: 92	Direct Replacement Halogen Bulbs I have been having problems with Direct Replacement Halogen Headlight Bulbs. I had a bulb go bad, I bought a new one from one of the A vendors and it was dim. It only burns one element. When I try my old bulb from the other headlight of the car in the same socket it works fine. The only difference I see in the bulbs is the shape of the contacts on the bottom. On my old one the contacts are football shaped. On the new vendor bulb they are round. The vendor sent me another one, it is dim in both headlights also. They want to say its a ground problem. But my old bulb works fine in both sockets. I wish I could remember where I bought my original halogen bulbs. Does anybody have an idea what the difference is in the contacts?

05-19-2015, 08:39 PM	#2
Ron/IA Senior Member Join Date: May 2010 Location: Amana IA Posts: 527	Re: Direct Replacement Halogen Bulbs If you could provide a photo of the bulb's bases; that would give the Fordbarn population more to work with. __________________ Ron/IA 1929 Fordor Steelback Hawk A Model A Ford Club http://hawkamodelaclub.org/

05-20-2015, 01:23 AM	#3
MikeK Senior Member Join Date: May 2010 Location: Windy City Posts: 2,919	Re: Direct Replacement Halogen Bulbs The problem is with your sockets, not the bulbs. The two brass socket contacts with springs under them become worn in their holes on original sockets. This allows them to be cocked sideways shorting to each other and/or the shell when the bayonet bulb is twisted in. The bulbs with football shaped contacts (BAY15B bases as opposed to BA15B) have a gentler ramp and are more forgiving to the socket contact side-play. The newer round bulb contacts(BA15B) tend to hang up on the two brass contacts and will twist them against the shell if they are loose in their holes through the fiber insulator at the socket base. Football contacts Round contacts To compound the problem, most of the reproduction sockets have larger contact heads and thinner, sloppier fit fiber bases that permit off-axis contact movement and thus will short easily. Applying a liberal amount of dielectric grease helps, and in this case it does more than act as a corrosion inhibitor. It acts as a lube. Make sure it gets under the socket contact rivets to lube them through the fiber base as well as on the bulb base contacts to prevent the lead solder from dragging the socket rivet contacts sideways when you twist the bayonet into its lock. Last edited by MikeK; 05-20-2015 at 08:05 AM.

05-20-2015, 05:00 PM	#4
BILL WILLIAMSON Senior Member Join Date: Dec 2010 Location: FRESNO, CA Posts: 12,560	Re: Direct Replacement Halogen Bulbs Sponsored Links (Register now to hide all advertisements) GREAT POST, Mike K, Sometimes a simple "trick" can save a lots of frustrating headaches & needless expense! Bill W. __________________ "THE ASSISTANT GURU OF STUFF"