Blowing out headlamps.

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Model T Ford Forum: Forum 2012: Blowing out headlamps.
Top of pagePrevious messageNext messageBottom of page Link to this message  By Matthew David Maiers on Tuesday, December 11, 2012 - 09:18 pm:

so i decided to clean the commutator replace the brush plate and install new brushes on my generator, cleaned it, under cut he mica, and chamfered each segment, reassembled and set the null point. set generator to charge at 1-2 amps whith lights on.

on my way into town, ammeter jumps to 5 then ten amps. so i flip the headlight switch over and it goes back to 1-2 amps. on the way back in town it does the same thing. so i thought "well those are old bulbs ill replace them, thatll fix it" then today half way to work, same thing happens, except the second filiment blew within a few minutes.

the method i used to se the null point was, lift the third brush, and rotate brush plate until it doesnt rotate, but has a tendency counter clockwise i think ( whatever glen chaffin said in a post).

i checked the battery at high idle, and it was at 6.5 volts.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Tuesday, December 11, 2012 - 09:36 pm:

It appears that you set the generator correctly. The lights will burn out if you have a bad connection between the ammeter and the battery. Your generator puts all the power into the bulbs and there is no battery to regulate the voltage so the lights burn out.

Check the connections behind the ammeter and also the terminal block and the starter switch and the battery. Often this happens when you have corrosion at the battery terminal or the cable is not tight at the battery. Any loose connection or open connection in any of those places will cause the problem.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Matthew David Maiers on Tuesday, December 11, 2012 - 09:42 pm:

you know i checked the battery connections, snd the positive was loose, and suspected tha could be a cause,

unfortunately ive burned hrough my stock of spare bulbs!


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Wednesday, December 12, 2012 - 07:53 am:

I had a Model A with a loose ammeter wire. My headlight would go out like flash bulbs and that is exciting when driving 50 mph at night. The tail light also burned out at the same time.

One night I saw a flash in the ammeter when they went out and fixed the problem.

I later learned that the generator could produce 36 volts, but not for long.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Wednesday, December 12, 2012 - 08:14 pm:

Matthew:

If you are using a battery "master disconnect switch" - those can be very problematic and also known to kill lights and generators. If you are using a mechanical cutout it can also give you readings that vary depending on how the points in the cutout "connect" at any particular time. Finally, I would not set your charge rate to 1-2 amps with the lights on if you are using a cutout since this will result in a daytime charge rate that is about 3 times higher than what is good for your battery.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Matthew David Maiers on Wednesday, December 12, 2012 - 09:25 pm:

I always have my headlights on, its the only way in my book if you drive at night regularly (i do). the cutout is a 20 amp diode.

i have a standard battery cable, but i noticed that the connection was loose, i have other things to do to the car righ now, but i will also check other connections from genny to the battery.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Wednesday, December 12, 2012 - 10:09 pm:

Re Blowing out the headlamps; Try driving with the headlamp door closed! LOL :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Wednesday, December 12, 2012 - 10:25 pm:

You mentioned you had 6.5 volts at high idle. What voltage do you have at high RPM? Are you measuring that voltage with a digital volt meter?

Lights are very sensitive to voltages higher than the rated voltage and their life is radically shortened by even small excursions higher than the bulb's design voltage. A generator/cutout system if set to charge with the lights on is pretty much guaranteed to be setting the voltage higher than the design voltage of the bulb once the battery is fully charged since the extra voltage then goes to the bulbs. Think about it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Matthew David Maiers on Wednesday, December 12, 2012 - 10:55 pm:

well i ran the engine up to an rpm where generator reached its maxium ouput at its current setting. and yes i had checked it with a digital voltmeter.

the problem is that my last set of bulbs lasted over a year, then i did what i did and now the bulbs are going out. arent most bulbs marked 6-8 volts? at 8 volts your battery would be cooked.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Thursday, December 13, 2012 - 12:36 am:

It matters not what bulbs are marked - the truth is that ALL tungsten filament bulbs in fact have one and only one design voltage at which their life is stated and their operate current and lumens (or candle power) of brightness are rated. No bulb will in fact operate between 6-8 and have the same specs at 6 as at 8.

If you measured your voltage with a digital meter then I would doubt the accuracy of any reading taken when the engine was running unless your T is running a distributor and shielded wiring or you are using resistance spark plug wires. Digital meters are typically interfered with by the ignition system and readings jump around and are simply not accurate. It matters not whether the digital meter is an expensive laboratory grade meter (I have some Fluke digital meters that fall into this category) or a cheap Harbor Freight digital meter (I have some of these too). It has to do with the type of sample and hold circuit that these digital meters use to take measurements and then digitize them for read out. I strongly suggest you get a cheap analog meter and use it to read your voltages if you want to see exactly what is going one when the engine is running.

If a bulb is rated at 6.3V which is a common design voltage for "6V" bulbs and then you operate that bulb with 8V source - you will get only 5.7% of that bulbs normal life compared to 100% of its normal life when operated at 6.3V Conversely if you were to operate that same bulb at 5 volts you would get 16 times longer life from it. Small voltages have a drastic effect on tungsten filament bulbs when you move away from the design voltage. This was shown dramatically during 1915-1917 when Ford tried to run 2 bulbs in series directly off the magneto. Those bulbs had a design voltage of 9 Volts each thus in series they became an 18V load. Thus when the magneto put out higher than 18 volts the bulbs began to burn out quickly. If the magneto could put out 28 volts it would result in the bulbs having .5% of their normal life which was in fact only 300 hours or so anyway. Thus they became flashbulbs when hooked up to a healthy magneto and the engine was revved up. At lower RPM the mag voltage is well below 18 so these same bulbs lacked brightness at slow speed driving. The magneto bulb idea didn't work very well until Ford put in the dimmer coil and wired them different but that is for another thread.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Thursday, December 13, 2012 - 01:44 pm:

It was most likely the loose cable which caused the problem. Since you regularly drive with the lights on, after you get everything working right, a voltage regulator would help keep the battery charged and would also decrease the voltage if you drive with the lights off. The problem with the original setup is that when you set the generator to charge with the lights on, it will overcharge when the lights are off, and when you set it to maintain a charge on the battery with the lights off, it will draw down the battery with lights on. And to add to the problem, the 3rd brush adjustment bolt when over tightened can damage the insulator causing generator problems, so it is not good to keep adjusting it whenever you drive with or without lights.
Norm


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