I need electrical smarts

notjustair

Well-known Member
I need help from the peanut gallery.

I'm talking about my 35 Chevy I frequently use for chores. My uncle let fall into disrepair and I'm slowly getting her back into shape as I use it. The truck has its original 12 amp generator with a cutout. It works as it should and has been verified to put out its full capacity. My question is how much lighting can I put back on it and still have it be able to keep up?

The original headlights are in place and work. Part of the issue is that they are rated in candle power and I'm not sure how to add that to the mix or know how many amps they will draw. Per the original specs the park lights are 3 candle power, the low beams are 21 candle power, and the high beams are listed as 21 also but the replacement bulbs are listed as 50 candle power for bright. I can see me upgrading to those newer bulbs. There are two dash lights which aren't much.

I want to add an orange marker to each front corner of the grain box, a red marker light to each corner of the back of the box, and the one tail light and brake light combination. These are all things it used to have. I have bits and pieces of the originals, but it's all pretty trashed so I'm going with new reproduction stuff for everything behind the cab.

Since there are so few lights I would like to add three red "clearance bar style" lights in the center of the grain box up under the back lip. I do use it on the blacktop between farms and it would be used after dark occasionally after it has lighting. Those six volt headlights will be barely adequate but I definitely want people coming up from behind to know I am there. It is registered antique so I can't go all crazy and add a bunch of stuff, though.

What should I be looking for watt-wise so I don't push the limits of the charging system? I have those candle power measurements for the front lights. I have the period correct tail/brake light fixture but it doesn't say what watt bulbs it uses. .
 
There is one candle power in one lumen.

There is roughly 15 lumens in one watt by the information I have found.

If that is correct your 21 lumen bulbs would be 1.3 or so watts.

So that bulb would pull about 1/4 of a amp. I find that hard to believe.

Use some led bulbs for clearance lights if you want low wattage lights to add to the truck.

Gary
 
I wouldn't think the markers are going to raise that much fuss. Now here is something to consider. Does you chevy have the two or three brush generator? You can diddle around with that but I would leave the regulator alone. They can be set if you have a very old and very good Chiltons manual. You need a good digital meter and also a good amp gauge in the dash. They are an art to get just right.
 
6v or 12v? Are 6v LED's available? LED's would really light it up with a low power draw but I don't know if you can get LED's in an older style lense to help keep it original looking.
 
A 7 inch 6006 headlight bulb is rated 40/50 watts for a 6 volt system. Thats around 8 amps per bulb on high and 6.54 amps on low. Meaning that your drawing 12.9 amps on low beam just from the head lights..

Your '35 model may have older style bulbs and draw much less and have very poor lighting. either way a 12 amp genny is not going do you much good. Did you mean to say its converted to 12 volts or is it a 6 volt system with a 12 amp generator. I would run at least a 22 amp generator as they were more common or get a commercial truck genny for that period that put out 40 amps to give you a chance of running marker lights, more modern halogen headlights as well as your other needs.
 

Also a 9006 12 volt head light puts out around 1000 lumens... so I dont know how a 6 volt headlight at 15 lumens would even work. Are you sure thats not watts or amps?? Lots of headlights were designed at 30 to 60 watts of power..or 2.5 amps to 5 amps per head light for 12 volt systems.. double the amps draw for 6 volt systems.
 
I struck out trying to convert candlepower to watts, too complicated for me!

But I did find some info on typical 6v lamp wattage. You can look through these lamps and get an idea what the wattage would be.

The headlights, are they seal beam or use a regular lamp? Possibly you can enter the replacement lamp number and get the wattage.

Once you have the total watt load, divide that number by 6. That will give the amp load.
6v lamps
 
I'm going off the spec sheet as far as the headlight bulb power. It lists them as both (low and high beam) 21 candle power, but the new
replacement bulbs are 21/50 candle power. I'm not sure how that comes out amp-wise. The 6 volt generator puts out 12 amps at 7.2 volts (this
is the "hot" rating - "cold" is 17 amps and 8.1 volts). Everything I could find online said there was no sure way to convert candle power to amps
or watts. I was sort of hoping someone had been in this situation before. It does have a three brush generator but uses a cutout rather than a
regulator I could fiddle with. Unlike some early tractors, there isn't a brush adjustment on the third brush to raise the charge rate.
 
There is no direct relationship between candlepower and watts. One is a measure of light(lumens in modern metric), and the other is a measure of work or power. I know, not much help.

There is a general rule of thumb that has been out of use for a long, long time. For a tungsten filament bulb in vacuum, one watt of power would produce about 4.8 candlepower at one foot(where we got the term 'foot candle'). If your beams are 21 candlepower, that would be 21/4.8 or about 4.2 amps per lamp.

Your generator should be of the 'lamp load' type and I think it was a 943J and the cutout should be set for 7.2 volts at 2100 RPM(highway speed in gear). The wire from the gen will go to the lamp switch so that when the lights are on, the lighting will present the load directly to the generator, to be more efficient.

If you want to improve things, you can take your incandescent lamps out, and replace with modern lighting, specifically LED. You would need to have a cross reference for each lamp unless you want to just wing it. Some 12 volt LED bulbs will illuminate at 6 volts, you just need to test them. There are many cross refs for 12V lamps, but few for 6V. I think your generator is rated for full current at highway speed of 16 amps. Derated for stop and go, and around town it would be 12 amps.

If you have a generator with exposed armature, that is a 'vented' unit and may be 22, 25, or even 35 amps. If you want to stay with stock, don't replace with the modern style headlights rated in watts. Your gen will not put out enough current, and the wires also are unlikely to support it. Remember, when you halve the voltage(12 down to 6), you need to just about double the current rating of the wires.

I had a 1937 Cord Beverly with a 35 amp 6 volt system. I was always having issues getting it to start, because I didn't take long drives, and sometimes I would use the tube radio, and heater with fan motor. The batt didn't hold up well. It's best once you start it to drive for a while, or keep the batt on a trickle charger at 6V

https://www.amazon.com/Decker-BM3B-Battery-Charger-Maintainer/dp/B0051D3MP6/ref=sr_1_2?ie=UTF8&qid=1484196389&sr=8-2&keywords=6+volt+trickle+charger

I use this for my 6 volt 8N.
 
Been to many year for me but there is a way to figure out watts/volt/amps. I.E. you have a 6 volt system and your generator puts out 12 amps so that will limit how many watts of light power you can have before it get to the point that the generator will not longer be able to over come the out going power in the lights and running of the engine. As I said not sure I remember this correctly but if I do and I figured it right you can use up to 72 watts of head light power and still break even but as I said been a longtime so that may not be correct
 
Remove the battery and use your battery charger in its place, then turn on the lights and the amp meter on your charger will tell you how many amps each item draws.
 
Old, that's right. Watts divided by volts = amps.

So, 72/6=12. At 72 watts total draw, the generator is maxed out.

He's wanting to have 4 corner lights @ 7 watts each. A tail light @ 13 watts. Two head lights @ (a conservative guess) 15 watts each.

That adds up to 71 watts! Not enough left for the ignition coil, and talk of an electric fuel pump.

Looks like a bigger generator is going to be a necessity.
 
From what I understand you want have somewhat modern lights but stay original as possible. Going with LED lights as much as possible for markers and tail would be the best way to say within your generator ratings. My experience on 6v machines (tractors) they barely kept up when running lights when all was well with the generator and battery.

Are these headlamps sealed beam or some type of insert bulb?

Can you upgrade the generator to a larger higher output 6v model (from another machine) to stay somewhat original?

If it were mine, based upon the fact you hope to use it on the road after dark I would upgrade to 12v with alternator and enjoy the convenience of 12v and run all the lights I thought I needed to make myself visible to other drivers.
 
Well I guess once in a while that old stuff I learned back in the 70s still come out of the dark area of the brain that has not been used in decades.
 
But isn't the 3rd brush how you set the volts? That eliminates the need for a regulator.

The amps is determined by the windings in the generator. It can only do what it was designed to do.
 

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