Burned Out Headlamp Bulbs

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Model T Ford Forum: Forum 2013: Burned Out Headlamp Bulbs
Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Perigo - Linton, IN on Monday, November 18, 2013 - 08:43 pm:

What causes Model T headlamp bulbs to burn out prematurely? There is no pattern that I can find. A new bulb burned out almost immediately with little usage. I thought it might be a poor ground, so I grounded both sockets with a separate wire directly to a point on the frame with a good ground. I'm running a 6V generator that charges around 5 amps.
What could be the cause?
Thanks,
Mike


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan B on Monday, November 18, 2013 - 08:57 pm:

Mike,

I had a problem with my headlight bulbs burning out too. I replaced the cutout with a Fun Projects voltage regulator, adjusted the third brush, and haven't had a problem since.

If you're charge rate is a constant 5A and never reaches zero, then I suppose that might be a part of the problem.

Dan


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Monday, November 18, 2013 - 09:15 pm:

I would believe the car's overall vibrations will shorten any light bulb's useful life.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Stitt-Southern Oregon on Monday, November 18, 2013 - 09:18 pm:

I don't think the charge rate matters as the device will pull what it wants so to speak. The voltage really matters so Dan is correct Fun Projects VR is what you need.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Perigo - Linton, IN on Monday, November 18, 2013 - 09:24 pm:

So, back in the day, not to be funny, but did they buy bulbs by the gross? I mean....I always thought that voltage stayed at 6 volts regardless of the charging rate in amps. I have used a fun projects regulator before and think they are great, but is voltage really the issue here?

Mike


Top of pagePrevious messageNext messageBottom of page Link to this message  By Clayton Swanson on Monday, November 18, 2013 - 09:45 pm:

my friends model a burned out lots of bulbs and it turned out to be the battery ground to the frame. car always started, never acted like a bad connection. the generator post was always hot too, like making current but no place for it to go


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Carter - South Jersey on Monday, November 18, 2013 - 09:45 pm:

Check the voltage at the bulb. If the connection between the generator and the battery has a problem the voltage can be much more than normal (~7.25 V).


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode Chehalis Washington on Monday, November 18, 2013 - 09:54 pm:

Mike,
A bad ground would likely make your bulbs last longer and the lights would be dimmer.

As said above, a higher voltage will shorten the life of the light bulbs. A fun projects regulator should control the voltage or depending on how much you drive with the lights on, a charge rate of 2 or 3 amps should be enough to maintain the battery without over charging.

A reasonable test for you would be to check the voltage that is being supplied to the lights. It should no more then about 7 when the engine is running. If the voltage being supplied to the lights is much more then the battery voltage, check for bad connections at the battery and between the battery and generator.

Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Monday, November 18, 2013 - 10:38 pm:

I think you have a loose connection or intermittent open in your charging circuit. The generator voltage will spike quite high in presence of an open.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Tuesday, November 19, 2013 - 12:11 am:

Most of the above posts are right on the money. The amperage is somewhat meaningless unless it is excessive and is driving the voltage way up even when the lights are on. If you have a substantial amount of charge when the lights are on then you have to have a rather large over voltage that goes with it most likely. The life of a bulb drops off very rapidly when you raise the voltage on it even a small amount above its design voltage. All tungsten filament bulbs (this includes halogen) have this problem. If a bulb is designed for say 6.3V and you apply 7.3V to it then you will reduce its life. If it is a bulb designed for 1500 hours when operated at 6.3V then its life at 7.3 will be 256 hours. If operated at 7.5V then its life will be 185 hours. Vibration does affect the life of bulbs but actually the lower the voltage of the bulb the tougher the filament is so a 6V bulb will stand a ton more vibration than would a household 125V incandescent bulb. 6V bulbs are more rugged than 12V bulbs of the same candle power and rated life.

Regulating the voltage has more affect on bulb life than does anything else. Regardless of how a bulb is marked it still has one and only one design voltage that is used for rating its life. I have seen folks think that they can use a bulb marked 6-8V and it will work fine with an 8V battery but nothing can be further from the truth. Nominal 6V automotive bulbs have a very short life when used with an 8V battery with its charging voltage of 9.3 - 9.4 If you rarely drive at night and are using a cutout - set the charge current very low (3-4 amps) and live with the discharge when driving with the lights on and your lights will last a long time. Charge the battery manually when you get home. You would have to drive all night to run the battery down. Putting the charger on it when you get home will bring it back up. Don't set the charge rate higher unless you have a voltage regulator on the car and then set it per the instructions and you should have bright long life bulbs and a fully charged battery.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Tuesday, November 19, 2013 - 12:16 am:

I meant to point out that Jim Thode has it 100% correct on all points he made. Bad ground extends bulb life. Higher voltage shortens life. I even agree with 2-3 amps as being better than 3-4 but nobody trusts their ammeter so they always set them to 5-6 and this is what shortens the life of things. I find that 3-4 advice is more often actually followed but I think Jim is correct at 2-3 amps when drive almost 100% day time driving.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim Wrenn on Tuesday, November 19, 2013 - 08:54 am:

FWIW, here's my story on burning out bulbs. When I bought my '20 Runabout, it had no brake light. Put in a brake light switch, modified the taillight of course to double filament socket, ran ground wire to frame from socket. Hooked wires up accordingly, bright filament brake, dimmer one, running light. OK, run a trip or two, blew out bulb. Cleaned all ground contacts again, including batt. to frame. Got better, then started in again. Ended up switching the wires, even tho I knew it shouldn't be that way, but it seemed to behave for a long long time, so left it go. Then it blew again. At about the same time I had started to smell a funny odor one day so checked out under the dash and found a bad, semi-burnt connection to the switch/ammeter. Replaced the whole loom and voila!....problem solved. Have even been able to put the wires back on the correct filament connection, and haven't had a problem since. Even the headlights are brighter!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim Wrenn on Tuesday, November 19, 2013 - 08:57 am:

OK...thought the previous post was getting kind of lengthy...so here's a question I have regarding ammeters and output of generator. Every T I have puts out 10 amps to start with, then slowly backs down to maybe 6 at best, hardly ever less, only on long trips. Seems like it hardly ever drops below 10 amps though, as frequently I'm only out driving around for maybe 20 minute "jaunts" before shutting down, and starting back up again to continue on. My friends is the same. But if I'm reading above posts correctly, seems like they should only read around 6 virtually all the time? Even upon starting the car and driving the first few minutes?


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Menzies on Tuesday, November 19, 2013 - 09:41 am:

Is there any way power from the mag is getting into the system, it can put out 18 volts? The old paper switch plates do get messed up over time. In the early cars the headlights were wired in series with 9 volt lamps (not available any more) if 6-8 volt lamps were used the life would be shortened. There was kits available to rewire them in series. The tail light was wired in series with the dash light @9 volts each so if the dash light was out so was the tail light. This was early technology that was changed for parallel wireing. It is possible with some wiring misadventure that some mag power is entering into the system. Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, November 19, 2013 - 10:04 am:

David, you can adjust the amps yourself with the third brush on the generator. 6 amps continually boils the battery and wears it out prematurely.
Buy the MTFCA book on the electrical system for $12, lots of good reading :-) http://modeltstore.myshopify.com/products/service-manuals

If you've got more to spend, the Fun Projects regulator is a good investment - it'll regulate the charging to just what the battery needs at every moment: http://www.funprojects.com/products/5055r.cfm

Most 6 volt batteries doesn't live very long, unfortunately. With the original cut out the battery is the voltage regulator. Should there be an internal short in the battery, then perhaps voltage might raise higher intermittently?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Tuesday, November 19, 2013 - 01:30 pm:

A loose or corroded ground at the battery could cause the bulbs to burn out, but not a bad ground at the bulb. However, since the starter worked ok, I would suspect there is a loose connection between the ammeter and the starter switch. That would leave the ammeter itself, the battery side of the ammeter, the connecting block on the firewall and the starter switch. If you have any fuses in the circuit, it could be a bad or open connection at the fuse. Not only would a loose connection cause a problem but a corroded wire end at the clip or broken wire could also cause it. What is likely to be happening is that the current is not going toward the battery, but instead it is directed toward the lights. Your generator and/or voltage regulator sees it as a dead battery and so pushes the voltage higher and burns out the lights.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Tuesday, November 19, 2013 - 02:14 pm:

If the VR is working correctly it will not allow the voltage to go higher when the load changes no matter how it changes. Only if the VR ground (mounting hardware) is loose could a good VR let the voltage go higher long enough to burn out the bulbs. Most of this discussion seem to be about generators equipped with cutouts since steady 6 amp charge under all conditions is either a cutout equipped car or a car with a defective VR. The initial current whether you use a VR or cutout will be higher than the final current. This is because the various components in the generator, ammeter, wiring, and switch are all made of copper and as the temperatures rise, so does the resistance of all those components and this causes the current to reduce by varying amounts. If you read the instructions that come with our VR's you will see there is a FINAL test (one that most folks never actually perform). That final test is to find out what the actual peak amp setting really is and to make sure it is 15 amps or less on a 6V system. This test is run when the entire car system is cool and is done immediately after the car is started with what is hopefully a fully correctly adjusted setup. Assuming that final test is good then no further adjustment of the generator is every needed again until the generator needs another rebuild which should not be in your life time.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Wednesday, November 20, 2013 - 02:33 am:

I'll add that the above all works and should be checked...but at the same time....take a look at the lamp bulb that died!

Did the filament explode? Did the filament look new but have a break?

Reason I say that is that old bulbs (and maybe some new ones for a different reason) have the glass sealed to the brass base with something that actually age hardens to brittle. Then the old turn to lock splits the seal and a lamp, any lamp that sees air lasts all of about a second!

I was using clear nail polish around bases as a safeguard, new seal, thicker seal, well dried...but then someone else told me to just use super-glue and dribble it at the seam and it flows around. Makes a tighter air free joint so when you twist it you don't break accidentally the seal.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Wednesday, November 20, 2013 - 02:50 am:

I'll add that the above all works and should be checked...but at the same time....take a look at the lamp bulb that died!

Did the filament explode? Did the filament look new but have a break?

Reason I say that is that old bulbs (and maybe some new ones for a different reason) have the glass sealed to the brass base with something that actually age hardens to brittle. Then the old turn to lock splits the seal and a lamp, any lamp that sees air lasts all of about a second!

I was using clear nail polish around bases as a safeguard, new seal, thicker seal, well dried...but then someone else told me to just use super-glue and dribble it at the seam and it flows around. Makes a tighter air free joint so when you twist it you don't break accidentally the seal.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Wednesday, November 20, 2013 - 02:52 am:

sorry...it does that sometimes....


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Wednesday, November 20, 2013 - 06:54 am:

That 6 volt generator can put out 36 volts, and if there is a bad connection in the link to the battery, all that voltage will turn your head light and tail light bulbs into flash bulbs, if they are turned on at the time and the link is open and the generator not allowed to charge the battery at that time.

A loose terminal on the ammeter or terminal block are the most common likely problem areas.

The loose ammeter terminal often identifies itself by setting the car on fire.


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