The Ford Barn

28 Special Coupe · 09-01-2010, 08:15 PM

I have some questions about how headlight bulbs should be installed. My bulbs have two filaments, one that's pointy shaped, and one that's flat. Which bulb is the high beam, and which one is the low beam? Which filament should be on top? I assume they should be oriented horizontally, correct? Thanks for you help.

msmaron · 09-01-2010, 08:28 PM

Yes horizontal and the larger filament is the brights, put them in and give a test that is the best way

Tom Wesenberg · 09-01-2010, 10:22 PM

As Mark said, if the filaments have a different size wire, the thicker one is high beam (brighter and draws more amps) and is located about in the middle. The low beam is located on top so the reflector directs the light rays downward more.

Also as Mark said, the filaments are horizontal. Be sure to FOCUS as well as aim the lights. Check Marco's webiste.

Aerocraft · 09-02-2010, 09:00 AM

If you are installing these bulbs in a '28 Coupe with the original reflectors they will not work as you would expect since the early lights did not have the high / low beam feature. The early reflectors had the bulb exactly centered while the later reflectors had the bulb slightly offset vertically. The service bulletins explain this much better than I can.

Also, it is my understanding that the original bulbs (I have several boxes of original bulbs which go off like flash bulbs when used) had both of the filaments "pointy shaped". My last order for bulbs arrived with one filament flat as yours are. I wonder what that does to the beam and would be interested to hear an explanation from an optics expert. Gar Williams

MikeK · 09-02-2010, 09:27 AM

Here are two pix of a Westinghouse Mazda 50/21 cp lamp with both filaments pointed like an inverted 'V'.

In the first pix you can clearly see that on the brass base one pin is marked "TOP".

In the second pix, slightly rotated, You see that the thinner filament will be up, or on top and the thick high beam filament on the bottom when installed correctly.

28 Special Coupe · 09-02-2010, 07:45 PM

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Thanks for your help, guys. Once you told me what to look for, it was a breeze to get right. The V shaped filament is centered in the bulb and is a little bit thicker, so it's obviously the high beam. The flat filament is offset in the bulb, so it's the low beam. I positioned the bulb with the flat filament on top and made sure the wiring was correct and it works like a charm! Thanks again.

Special Coupe Frank · 09-03-2010, 06:19 AM

Don't be alarmed if your low-beam ( flat straight filament ) doesn't last very long....

I bought about a dozen 50/32 CP bulbs from one of the major vendors this spring, and went through about eight of them, the low beams failing after anywhere from 1/2 hour to a couple days. The bulbs are made in China.

The "pointy" high-beam filament seems to last longer.

Just for yuks, I tried some ancient (1930's) bulbs that I found in the garage, and those have lasted the longest so far, several months.

I am in the habit of always driving with my headlights on ( hoping that helps other drivers see ME ! ), so I probaly use my lights more than the average Model A owner.

I drive my Ford quite a bit, 3000 miles since January.

SC Frank

09-01-2010, 08:15 PM	#1
28 Special Coupe Member Join Date: Jun 2010 Location: Broken Arrow, Oklahoma Posts: 63	Headlight bulb questions I have some questions about how headlight bulbs should be installed. My bulbs have two filaments, one that's pointy shaped, and one that's flat. Which bulb is the high beam, and which one is the low beam? Which filament should be on top? I assume they should be oriented horizontally, correct? Thanks for you help.

09-01-2010, 08:28 PM	#2
msmaron Senior Member Join Date: May 2010 Location: Wauconda, IL Posts: 3,600	Re: Headlight bulb questions Yes horizontal and the larger filament is the brights, put them in and give a test that is the best way __________________ Mark Maron Ill., Region MARC & MAFCA MARC JSC Member MAFFI Trustee National Facebook Admin. https://www.facebook.com/groups/MARC.group/ A7191-Sport Coupe 29 Roadster 29-Town Sedan 29-Original Special Coupe

09-01-2010, 10:22 PM	#3
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Headlight bulb questions As Mark said, if the filaments have a different size wire, the thicker one is high beam (brighter and draws more amps) and is located about in the middle. The low beam is located on top so the reflector directs the light rays downward more. Also as Mark said, the filaments are horizontal. Be sure to FOCUS as well as aim the lights. Check Marco's webiste.

09-02-2010, 09:00 AM	#4
Aerocraft Senior Member Join Date: May 2010 Location: Naperville, IL Posts: 1,387	Re: Headlight bulb questions If you are installing these bulbs in a '28 Coupe with the original reflectors they will not work as you would expect since the early lights did not have the high / low beam feature. The early reflectors had the bulb exactly centered while the later reflectors had the bulb slightly offset vertically. The service bulletins explain this much better than I can. Also, it is my understanding that the original bulbs (I have several boxes of original bulbs which go off like flash bulbs when used) had both of the filaments "pointy shaped". My last order for bulbs arrived with one filament flat as yours are. I wonder what that does to the beam and would be interested to hear an explanation from an optics expert. Gar Williams

09-02-2010, 09:27 AM	#5
MikeK Senior Member Join Date: May 2010 Location: Windy City Posts: 2,919	Re: Headlight bulb questions Here are two pix of a Westinghouse Mazda 50/21 cp lamp with both filaments pointed like an inverted 'V'. In the first pix you can clearly see that on the brass base one pin is marked "TOP". In the second pix, slightly rotated, You see that the thinner filament will be up, or on top and the thick high beam filament on the bottom when installed correctly.

09-02-2010, 07:45 PM	#6
28 Special Coupe Member Join Date: Jun 2010 Location: Broken Arrow, Oklahoma Posts: 63	Re: Headlight bulb questions Sponsored Links (Register now to hide all advertisements) Thanks for your help, guys. Once you told me what to look for, it was a breeze to get right. The V shaped filament is centered in the bulb and is a little bit thicker, so it's obviously the high beam. The flat filament is offset in the bulb, so it's the low beam. I positioned the bulb with the flat filament on top and made sure the wiring was correct and it works like a charm! Thanks again.

09-03-2010, 06:19 AM	#7
Special Coupe Frank Senior Member Join Date: May 2010 Location: Northeast Penna Posts: 2,108	Re: Headlight bulb questions Don't be alarmed if your low-beam ( flat straight filament ) doesn't last very long.... I bought about a dozen 50/32 CP bulbs from one of the major vendors this spring, and went through about eight of them, the low beams failing after anywhere from 1/2 hour to a couple days. The bulbs are made in China. The "pointy" high-beam filament seems to last longer. Just for yuks, I tried some ancient (1930's) bulbs that I found in the garage, and those have lasted the longest so far, several months. I am in the habit of always driving with my headlights on ( hoping that helps other drivers see ME ! ), so I probaly use my lights more than the average Model A owner. I drive my Ford quite a bit, 3000 miles since January. SC Frank