Charging

Bill Davis · May 31, 2009, 09:32:27 PM

Well said, Plymouths. You make some valid points.

It actually is current (amps) that causes our grief, not voltage.

FourDoor · May 26, 2009, 01:15:18 PM

And just my 2 cents worth on a subject that continues to frustrate owners.
I think we're 'reinventing' electricity theory and not for the better. The old mechanics, and the old magazines, always talk about 'current' and never,ever discuss 'voltage'. Ever. They always broke open the circuit and placed an ammeter in series with the problem area and checked for current flow. Always.
It's gets very technical but you can have a voltage showing at a circuit node with 1 milllion ohms of impedance in series with it which will allow only a few microamps to flow under an actual load. (The 1 megaohm impedance could be caused by a corroded circuit point ANY place in the car.)You will scratch your head for a long time unless you keep the voltmeter on the circuit point and watch the voltage collapse under load and realize what just happened. The input impedance of a modern digital V-O-M meter is over 10 megohms on? the voltage scales. It will lie like hell on the actual ability of the circuit to allow current to flow. You require a different set of troubleshooting abilities if you are going to use 'voltage' as your basis for problem solving.
Many modern troubleshooting techniques are based on computer troubleshooting where you do not break open the circuit because of the printed circuit construction of the boards. This is fine and necessary in the modern world. But I've noticed it's crept into the old car hobby and is causing a lot of grief to the layman trying to fix his car's charging system. Voltage checks are fine when you've corrected all the errors and you want to see what the system stabilised at- 7.5 volts or 14.8 volts.
But troubleshooting low impedance systems like this has to be done with that low impedance in mind. And low impedance means 'current'. Lots of current. Again, unless you have the training to understand voltage drops ,and are able to follow them logically through a circuit, do what the old mechanics did and break open the circuit, put an ammeter in circuit, and watch for current flow. It will be immediately obvious to you what to do depending on the amount of current.
? If you notice all the old left over meters from those bygone days are not volt meters. They're ammeters. Ever notice that at a flea market? They had access to volt meters but they didn't use them to any extent. They had their reasons and I think we're making the troubleshooting of these old 6 volt systems entirely too difficult trying to apply modern troubleshooting methods to very low impedance,high current, construction. Let's put it another way. If you could suddenly transport your car back 70 years to a shop in the 1930s, I think you would have your eyes opened when the mechanic started troubleshooting your electrical system.?
None of this is meant to detract from the help given here but just to steer us away from using voltage as the trouble shooting mode. You will find your life much simpler if you use, and think, current.? ? ?? ? ?

Lew · May 25, 2009, 05:48:39 PM

Just to add to all the other replies: before converting to an alternator system for my'36, my generator system performed the same way.Also, a car sitting for sometime or if not driven or charged regularly exhibits battery drainage through the chassis, etc. I installed a battery cut off switch on the floor in front of the driver's seat with at least 2/0 wire (needed for 6 volts) and copper ends available at many parts stores or an electrical supply store.(Some other excellent Bulletin posts covered this.) This avoids having to access the engine compartment for later cars or under the seat to access the battery itself, like on the '36's.
When parking, etc, you just cut off the juice, which also acts as a theft deterrent.

36 Ply · May 23, 2009, 09:23:59 AM

Carmen,

I just reread your original post below.

An original (tube type) radio will draw a lot of current. Even though my '36 has a 1942 generator and voltage regulator (installed before I owned it, probably because of the electric fuel pump), the ammeter pointer is dead center with the radio and headlights on at 25 mph. It's not discharging, but it's not charging either. At idle, it would be discharging 10 amps or more.

Bill Davis posted a good explanation of what voltage you should look for under specific conditions, and Tod Fitch and Bill Davis made a good point; make sure that something is not draining your battery with the ignition "off". I had a '46 Dodge pickup that did this; it turned out that the cab marker lights were shorted out.

Regards,
Pat O'Connor

Carmen · May 22, 2009, 09:47:04 AM

Thanks for all the tips. I am printing all of this out out so I can take it to the garage with me, my small brain can't remember all of it.

Carmen

Bill Davis · May 21, 2009, 11:19:58 PM

Carmen,

When you connect the ground cable to your battery, is a spark seen at the battery post?
If so, this is a good sign of something "draining" your battery when both battery terminals
are attached.

To expand a bit to what Pat O'Connor said, the volt meter should read about 6.2 volts
with the engine off (across the battery terminals) and about 7.2 - 7.5 volts across the
battery terminals with the engine running at "high idle".

Generator test: With engine running, momentarily ground the "Field" post of the
generator using a short jumper wire with "aligator clips" at each end. Note the
reading on your amp meter on the dashboard. If the amp meter shows full charge,
the generator is O.K. The "Field" post on the generator on my car is the one next
to the engine.

Hope this helps.

Go Fleiter · May 13, 2009, 12:41:10 AM

Most suspicious is the Voltage regulator , too.
If You have a spare, put it in and just try to check the difference between the performance of the two.
Does Your car have a Am Meter? it may not be very exact, but shows the direction of current to or from the Battery.
Gives an impression, if generator and Regulator are loading.
Great help is an external Am Meter. It must have 50 or 100 Am size. (100, if You want to check the starter or top motor too)
Greetings! Go

TodFitch · May 12, 2009, 11:11:44 PM

Quote from: 36 Ply on May 12, 2009, 09:20:46 PM
Carmen-

If you have a voltmeter (preferably digital, they are more accurate), you can check to see what your battery voltage is with the engine off, engine running, and each accessory "on" (one at a time); you may find a short this way, or excessive voltage draw when one of the acessories is "on". This may give you a clue as to how much accessory load your generator can handle, or if one of them is draining the battery more than it should.

Regards,
Pat O'Connor

And during this check verify that something is not draining the battery when the engine is off.

36 Ply · May 12, 2009, 09:20:46 PM

Carmen-

If you have a voltmeter (preferably digital, they are more accurate), you can check to see what your battery voltage is with the engine off, engine running, and each accessory "on" (one at a time); you may find a short this way, or excessive voltage draw when one of the acessories is "on". This may give you a clue as to how much accessory load your generator can handle, or if one of them is draining the battery more than it should.

Regards,
Pat O'Connor

RC Drown · May 12, 2009, 06:11:35 PM

Is the generator working ok?

How old is the battery?

Carmen · May 12, 2009, 01:12:45 PM

I have a 1941 P12 four door I am working on. I have replaced all the spark plug wires, had the starter rebuilt, new battery, new battery wires, new water pump and all the hoses. The car started up just fine every time.

This week I add turn signals, got the horn to work and installed the rebuilt radio. But now it seems that the battery is not being charged. Its on the charger right now.

In stead of driving the car home for lunch, I have to sit here and ask for help. What should I look for. Something seems to be draining the system.

Thanks

Carmen