VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 1931 headlight

I am rebuilding the headlights. That means all new electrical wiring and connections and re-chrome and reflectors have been aluminized. Now the questions is when I put the bulb in is the high beam filament up or down? Another question are there any gaskets used in putting the lens and reflector in the light buckets?

What bulb are you using? My repair manual indicates the candle power of both filaments is the same so it would not matter. The location of the filament is what gives you high or low beam as one filament is on center and the other slightly higher. The lens does use a cork gasket, otherwise water leakage would be a serious problem.

I have been useing 50-32CP headlight bulbs for years.

I ran into the same problem when replacing the bulbs on my 31. I had rewired the headlights after pack rats ate the wiring. I was using the 32-32 candle bulbs. I ended up with one on high beam and one on low beam. The bulbs will fit either way in the socket. I found by turning on the lights with them shinning at the wall and turning one of the bulbs over. They then were at the same for high and low beams. Chuick

I don't think the orientation of the bulb was the problem, rather the wiring to the socket was reversed. In the case of a bulb with different candle power filaments the filament of higher rating would need to be in the center. The upper filament would be the low beam due to the curvature of the reflector regardless of the candle power.

That is actually not correct. The headlight wiring can be reversed and the same problem will exist. The headlight bulbs are not indexed so they can be put in either way resulting in one on high beam and one on low beam instead of matching.

Ok I have located one 50-30 bulbs (I may have more) and many 32-32 bulbs. Having looked at all the bulbs it doesn't appear to me that one filament is more centered than the other. So I am still confused as to how to set up the wiring and how to put the bulbs in.

I agree and from reading the service manual it appears both bulbs could be installed incorrectly even if the wiring was correct as the bulb has two filaments- one on center and one above it, versus if incorrectly installed with one on center and one below it. If I sound confused it's because I am. I'm thinking that on high both filaments operate and on low only the upper filament operates. Enlighten me if incorrect.

I checked that on my '32 and either on high or low only one filament works at a time.

I am looking at my bulbs one 50-30, three 50-37 and eight 32-32 and all the filaments appear to be centered equally. Neither filament appears to be more centered than the other. If only one filament works at any one time then it is critical to have the bulb oriented properly.

There are two leads going to each socket, terminating with a 1/2" round insulator with 2 contact points, and the dimmer switch determines which lead is powered. The powered lead lights one filament and then goes to ground. It is the offset of the filaments within the bulbs which determines whether hi or low beam, or perhaps they are of different candle power, I have not checked mine.

If I recall, the bulb will only go into reflector socket one way as it has ofset prongs. As a result, if you wind up with a hi on one side and a low on the other you need to rotate the end of the leads 180 degres as they sit in the socket. If I recall, my harness from FS had these leads marked H & L so if you install them in reflector sockets with the same orientation for each side they work perfectly.

The prongs on the bulbs are not offset and the bulb can be placed in the socket in two different orientations. The leads in the socket cannot be rotated 180 because the sockets fit into the reflector in only one position. The leads can only be fit into one position in the sockets because the slots on either side are a different size. One is larger than the other. This is why I asked the questions about how to wire and how to place the bulb? The results can lead to problems if not put in properly.

Paul -

With the headlight lens off both headlights, here is what I have done on my 31. I have no high beam indicator on dash to tell me if I am on high or low beam.

You have three wires inside headlight housing. One goes to the park light and other 2 go to the bulbs. Looking at the bulbs, you will see the 2 filaments stacked inside. Turn on your headlights. Hook up one of the two wires to the bulb. See which filament is lighted. Go to the other side and do the same only making sure the same filament is lighted on the second bulb. Now hook up the other hot wire to the bulb on both sides and see if the same filament is lighted on both bulbs. That is how I figured it out. There is one filament in center of bulb and the other is just above it. Without a high beam indicator, it doesn't make any difference what you do with the dimmer switch. The high beam will throw a higher pattern on a wall than the dim side. The dim side throws downward and toward the shoulder of the road. On mine, that was the centered filament in the bulb with the upper filament in the stack the bright side. As Mr. Dog pointed out, you will only have one filament on bright and only one filament on the dim side. Its the pattern in the glass that denotes the difference in the bright or dim side.

If I didn't confuse you, I'm glad and the best to you.

Jim.

Jim, there appears to be some sound logic in what you are saying. If in fact the dimmer switch operates as you say then it would seem logical that the only important issue is that both lights are wired the same. Upper filament on for both at the same time and the same for the lower filament. Then getting the orientation of the bulb becomes the last issue to deal with.

The filament positioned at the focal point "sweet spot" for the reflector is the high beam and the other is just off the focal point giving less light.

Yup, see, it only took you 3 lines to the answer and I took about 20 lines. Hmmmmm. Tell you something??

Chipper -

I bow to your knowledge and I believe you are also an engineer, and that being said, according to manual, both filaments put out the same candle power, so wouldn't the light be the same from both elements with the only difference being the refraction of the light to a different position through the lens??

As I have mentioned above and as others have stated also, the headlight bulbs can be inserted into the socket either way since the prongs are equal and not offset. In other words, the bulbs are not indexed to be inserted in only one position.

Oops!, my bad regarding my posting, was going from memory, and we all know that is not wise. I think I was getting my recall of the headlights contacts confused with the ends of the cowl lights, which are only a single contact. Glad to see others with more experience or better memories have provided sound advice.

Being somewhat confused caused me to do a little reading. First the 29-32 service manual states " The candle power of each filament is the same; therefore the deflection of the light beam from the upper filament to the lower does not affect the brightness of the beam". If the bulb is a 32-32 or other equal filaments then the light output is equal from either filament and the positioning and reflection of the beam is what determines high or low. From Automotive Electrical Equipment by William H Crouse-1963 regarding the low beam filament " It is so placed with respect to the reflector that, when it is lighted, the light beam is directed somewhat more sharply downward than is the driving beam. The filament is offset so that the light is shifted slightly to the right".

That is some great information!

Now...the next question: Is the offset filament positioned above or below the center filament.....or does it make any difference as long as both bulbs are positioned in the reflector the same?

I am thinking it has to be above for the curvature of the reflector to properly direct the beam. It actually is fairly easy to comprehend if you use a flashlight. If set horizontally on a flat surface the beam is straight ahead. To aim the beam downward and to the right (passing or low beam)you will need to raise the rear of the flashlight and turn it slightly to the left.

That is my thinking also and the offset filament in my '32 is above the center filament.

The total light sent forward from the reflector on low beam (an offset filament) will be the same regardless of whether the low beam filament is above or below centerline, since the parabolic shape of the reflector is the same all around. As indicated, the offsetting of the filament is what reduces the total amount of light as opposed to having the filament on centerline which maximizes light output.

Now if one was to ask if there is a difference in the line of the light (the so called flashlight dipped idea) as a result of the filament being a hair below or above center, I am not sure.

My knowledge of physics and light reflection, leads me to believe a filament below center would reflect stronger off the lower half of the reflector causing the general light line reflection to be reflected slightly upward as it bounces off the lower hal;f of the reflector. The reverse would be true for a filament in the upper half. So by deduction, having the filament in the upper half (above center) seems best if any difference at all. But what do I know, I have been wrong so far in this posting!

Gunsmoke - I belive you have it right. For an in depth discussion on auto headlights go here:

http://what-when-how.com/automobile/headlight-automobile/

The upshot of this article, relating to a filament being offset above or below the center focal point, is illustrated as:



So, the filament being offset above the center will produce a "low beam" effect. Now, after it warms up a bit, I'll have to go out and see how mine are set up.

Happy Motoring,

Dan

This has been very informative. Applying a little bit of physics seems to answer the question. So, if I understand this properly, both lights should be inserted so that the slight offset of the filaments is pointed up. When the upper filament has power it will result in a low beam effect. When the lower filament has power it will result in a high beam effect. So now I have my answers.

Thank you very much for all this invaluable information.