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Wisconsin Engines Single cylinder up to V4 engines.

Wisconsin Engines

Wisconsin THD electrical question


I have an older Wisconsin 2-cylinder engine, model THD. It is fitted with a 6V positive ground...

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  #1  
Old 06-23-2009, 01:42 AM
metalmagpie metalmagpie is offline
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Default Wisconsin THD electrical question

I have an older Wisconsin 2-cylinder engine, model THD. It is fitted with a 6V positive ground generator with aftermarket solid-state voltage regulator. This generator is gear-driven and the engine's distributor is mounted to the generator's case.

The machine it is in has been converted to a 12V negative ground system. The engine starts fine and runs OK, but the charging system, naturally, is inactive.

The machine has been set up this way since at least 1994.

I am wondering if it's even possible that the old generator might be able to be fixable. Here is the (simple) circuit from
the manual:
http://www.tinyisland.com/images/tem...onsinFig18.jpg

The other question I have is that the coil appears original, which would mean it's a 6V coil. There is no ballast resistor in series with its primary circuit, which suggests to me that it may be drawing about twice its designed current. Can any of you suggest a method to determine if a ballast resistor is indicated and if so which one I should get?

I have all the relevant part numbers and can take pretty much any measurements.

I'm new to this forum and hope I'm posting this to the correct place. Thanks!

metalmagpie
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  #2  
Old 06-23-2009, 08:54 AM
K D Redd K D Redd is offline
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Default Re: Wisconsin THD electrical question

Remove the coil from it's mounting braket. See if it is marked with a voltage. Older coils were marked. Newer one may or may not be marked with their operating voltage.

Kent
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  #3  
Old 06-23-2009, 10:22 AM
metalmagpie metalmagpie is offline
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Default Re: Wisconsin THD electrical question

The coil isn't marked other than Autolite, Made In USA, and '-'.

metalmagpie
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Old 06-23-2009, 03:11 PM
pops pops is offline
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Default Re: Wisconsin THD electrical question

On a battery/coil ignition system, you gotta run a ballast resistor (unless the ballast is inside the coil like a older VW). Get an early 70's dodge or GM ballast, also hot rod shops have em. Without a ballast, too much current flows through points. This is sudden death to the points and wiring. Prolly won't hurt the coil. Also, be sure coil is for points ignition and not transistor ignition. Transistor coil has lower primary resistance (draws more current). You can measure primary easy, disconnect wire from coil -, hook ammeter; red lead=coil -, black lead=wire from points. Turn ignition on, rotate distributor until points close. Current should be less than 2-3 amps. Good luck, James
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Old 06-23-2009, 03:21 PM
FarmallBob FarmallBob is offline
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Default Re: Wisconsin THD electrical question

If your engine is wired per the diagram, what you describe as the “solid state regulator” is actually just a large diode. It’s only purpose is to prevent the battery from discharging back through the generator when the engine is stopped or running to slow to charge the battery The generator itself "runs wild" with no output regulation. Instead the battery provides crude voltage regulation by absorbing the excess generator output.

Consequently the existing generator may be able to charge a 12 volt battery with no modification whatsoever. (I've done it on an old Wisconson and a couple ancient 6 volt light plants). Suggest trying this:

Disconnect the wire from the generator output terminal (terminal should be labeled A or ARM). If the generator has an F or FLD terminal, use a temporary jumper wire to ground this terminal. Now take a VOM or DMM, place one probe on the generator A terminal, ground the other meter probe and set the meter to read DC volts.

Now start the engine, run it to full RPM and note the meter reading. If the meter shows 15 volts or more it should charge your 12 volt battery without modification.

If the meter shows less than 12 volts it’ll only charge a 6 volt battery and you're out of luck.

However if it shows less than about 8 volts the generator itself is NOT working – perhaps a visit inside to determine why (worn out brushes, dirty commutator, etc.) is in order.


Quote:
Originally Posted by metalmagpie View Post
Can any of you suggest a method to determine if a ballast resistor is indicated and if so which one I should get?
With the engine stopped use your VOM or DVM to take a current reading thru the coil with the 12 volt battery hooked up.

If you get a current reading greater than about 3 - 4 amps, the coil is 6 volt and a ballast resistor should added to limit the current to this value.

A ballast resistor for any 1960 thru mid 80’s Chrysler vehicle - about $15 at NAPA - will work fine. -OR- you can simply purchase a new, internally-ballasted “12 volt” coil (about $25) and dispense with a separate resistor.
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  #6  
Old 06-23-2009, 08:25 PM
metalmagpie metalmagpie is offline
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Default Re: Wisconsin THD electrical question

Quote:
If your engine is wired per the diagram, what you describe as the “solid state regulator” is actually just a large diode. It’s only purpose is to prevent the battery from discharging back through the generator when the engine is stopped or running to slow to charge the battery The generator itself "runs wild" with no output regulation. Instead the battery provides crude voltage regulation by absorbing the excess generator output.

Consequently the existing generator may be able to charge a 12 volt battery with no modification whatsoever.
Well, my engine has been modified from positive ground to negative ground.

Quote:
Suggest trying this:

Disconnect the wire from the generator output terminal (terminal should be labeled A or ARM). If the generator has an F or FLD terminal, use a temporary jumper wire to ground this terminal. Now take a VOM or DMM, place one probe on the generator A terminal, ground the other meter probe and set the meter to read DC volts.
Remember, I'm running negative ground now. If I jump the field to ground, won't that ensure zero output?

Quote:
Now start the engine, run it to full RPM and note the meter reading. If the meter shows 15 volts or more it should charge your 12 volt battery without modification.

If the meter shows less than 12 volts it’ll only charge a 6 volt battery and you're out of luck.

However if it shows less than about 8 volts the generator itself is NOT working – perhaps a visit inside to determine why (worn out brushes, dirty commutator, etc.) is in order.
I will try this as you wrote it. Maybe I'm not understanding something, but your instructions are quite clear. Thanks!

metalmagpie
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  #7  
Old 06-23-2009, 10:31 PM
metalmagpie metalmagpie is offline
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Default Re: Wisconsin THD electrical question

I haven't tried measuring the output voltage yet, but I'm wondering - if there isn't any voltage, or if it's the wrong polarity, isn't there some way I can flash the generator to make it run the other polarity?

I'm not clear on how the field is run - it must be run in series since the generator seems to only have two terminals - a wire labeled ARM and the ground connection.

I will take the measurement tomorrow and report back.

metalmagpie
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Old 06-24-2009, 08:56 AM
K D Redd K D Redd is offline
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Default Re: Wisconsin THD electrical question

There are two circuit, A and B, that are used in internal DC generator wiring. In one to make the generator poduce electricity YOU CONNECT THE FIELD, FLD, WIRE TO THE CASE OF THE GENERATOR. The other circuit you CONNECT THE FLD WIRE TO THE ARM. TERMINAL. If you do not get around 20 volts on a 12 volt generator when you do this, you need to vist a shop that rebuilds starters, genertors, and alternator. This WILL NOT be your local auto parts store.
If you do have a 6 volt genertor they might be able to rework it into a 12 volt model.

Kent
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Old 06-24-2009, 09:47 AM
FarmallBob FarmallBob is offline
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Default Re: Wisconsin THD electrical question

Quote:
Originally Posted by metalmagpie View Post
...isn't there some way I can flash the generator to make it run the other polarity?
Yes!

Connect the battery grounded for the system polarity you desire. Then with the ignition switch off, use a temporary jumper wire to momentarily connect the UNGROUNDED battery post to the generator "ARM" terminal. The instant the jumper makes contact (you may see a small spark...) the generator is successfully polarized.

Quote:
Originally Posted by metalmagpie View Post
I'm not clear on how the field is run - it must be run in series since the generator seems to only have two terminals - a wire labeled ARM and the ground connection.
The field windings are connected in PARALLEL with the armature. IE. one side is connected to the ARM terminal; the other is grounded inside the generator case.

Quote:
Originally Posted by metalmagpie View Post
Remember, I'm running negative ground now. If I jump the field to ground, won't that ensure zero output
Quite the opposite! On a "type A" field circuit - which most older generators are - grounding the field terminal drives the generator to maximum output. Conversely opening the field circuit causes generator output to drop to near 0.

...FB
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Old 06-24-2009, 03:30 PM
metalmagpie metalmagpie is offline
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Default Re: Wisconsin THD electrical question

OK. First off, I measured DC amps in my coil's primary circuit, now that I'm pretty sure I have a 6V coil in a 12V setup. As I expected, the current was high - 8.4 amps. I headed to NAPA and picked up a Mopar ballast resistor. Wired in, that took the primary current down to 4.4 amps. I checked, the motor starts OK even with the ballast resistor in the circuit, so I'll try it for awhile without a bypass network for starting.

OK. Since my generator's terminals seem to be labeled ARM and BAT, it appears that my Autolite generator is of the type where the field current is modulated by varying the resistance to the battery. My understanding is that to flash this type of generator, you momentarily jump the BAT and ARM posts. My understanding further is that to measure the generator output, you measure with your voltmeter between the ARM post (whose wire goes into the generator case) and ground.

I did this with the motor running, with and without the BAT post wire connected, before and after flashing the generator.

In no case did I get over 60 mV, in other words no significant voltage. This with the engine at about 80% of full rpm.

Now I'm wondering if I made the voltage measurement correctly, and also if I flashed the generator correctly. I've been running this machine for several years now by just charging the battery and running off the battery, and I could easily keep going. On the other hand, I could try to fix the generator. The third possibility is just to hack in an alternator with internal voltage regulator and be done with it.

metalmagpie
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Old 06-24-2009, 04:01 PM
FarmallBob FarmallBob is offline
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Default Re: Wisconsin THD electrical question

Quote:
I headed to NAPA and picked up a Mopar ballast resistor. Wired in, that took the primary current down to 4.4 amps.
That's perfect!

Quote:
I checked, the motor starts OK even with the ballast resistor in the circuit, so I'll try it for awhile without a bypass network for starting.
Don't worry about wiring in a starter bypass. It's only required to reliably start high performance, hard to crank V8 engines in cold weather. Your THD will start fine without the resistor bypass!

----

Find some helpful information and photos on Autolite type B generator identification, troubleshooting, etc here:

http://www.cj3a.info/tech/charging.html

...FB
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Old 06-24-2009, 04:19 PM
metalmagpie metalmagpie is offline
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Default Re: Wisconsin THD electrical question

I'm still having trouble understanding this generator. It doesn't seem to have enough wires coming out. There is one wire that comes out, which connects to the post labeled ARM on the voltage regulator (a Transpo D100, long obsolete). There are no other wires. Presumably the ground connection via the frame of the generator is the other connection.

The post on the other end of the voltage regulator (which is said to have its case isolated) says BAT and is in fact connected to 12V.

Very weird.

metalmagpie
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Old 06-25-2009, 08:43 AM
K D Redd K D Redd is offline
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Default Re: Wisconsin THD electrical question

What you are calling a voltage regulator MAY BE a cut-out relay, which can be rep;aced with a diode. COULD YOU POST SOME PICTURES. I have a "typical" wiring diagram for a TWIN in a INTERTEC manual. The connection on the cut-out relay goes to the amp meter, if equipped. No amp meter,connector the positive side of the battery.

Kent
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  #14  
Old 06-25-2009, 09:38 AM
metalmagpie metalmagpie is offline
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Default Re: Wisconsin THD electrical question

It probably is a cutout relay. In fact, the manual calls it a cutout relay in several places. My wiring is exactly as you describe. It will take me some time to get a picture or two posted, but I will get 'em.

Thanks, metalmagpie
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Old 06-25-2009, 09:42 AM
FarmallBob FarmallBob is offline
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Default Re: Wisconsin THD electrical question

Quote:
I'm still having trouble understanding this generator. It doesn't seem to have enough wires coming out.
Most likely the generator's field circuit is totally internal to the generator. The field winding taps power from the output (ARM) circuit (or from the 3rd brush if the generator if the generator has one); the other end is simply grounded inside the frame.

With this setup the generator "runs wild" with no voltage regulation whatsoever. But since it's max output is probably only 8 - 10 amps it's not a big deal. The battery will absorb the excess - though at the expense of somewhat shortened battery life.


Quote:
the voltage regulator (a Transpo D100, long obsolete)
FWIW the Transpo D100 is a cutout and not a voltage regulator. It consists simply of a large diode inside an insulated tin can with both terminals brought out. It crosses to the Wagner D09-00 and several others. Tractor Supply also stocks a generic equivalent.

...FB
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Old 06-26-2009, 12:03 AM
metalmagpie metalmagpie is offline
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Default Re: Wisconsin THD electrical question

While I didn't work on the charging system, today I changed the plugs, plug wires, points, condenser, distributor cap and spark plugs. I also set the timing, which had been off by about 10 degrees. This old THD is running sweet now! It still spits a little as I back the rpms down from top, probably a carburetor
issue. I also discovered that the tube from the air filter to the carburetor was half off and appears to have been that way for a long time. :-(

But it runs way way better, and with the ballast resistor I shouldn't have to keep monkeying with the points the way I've had to in the past. I thought the points were getting corroded from sitting. Now I think they were pitting from breaking too much current. Anyway, time will tell.

Time to put this old gal to work, enough primping.

metalmagpie
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Old 06-26-2009, 02:19 PM
FarmallBob FarmallBob is offline
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Default Re: Wisconsin THD electrical question

Quote:
It still spits a little as I back the rpms down from top, probably a carburetor.
That's pretty much normal. It's the result of the ignition not having a vacuum advance.

So long as the engine starts easily and pulls good under load I wouldn't worry about it!

Quote:
with the ballast resistor I shouldn't have to keep monkeying with the points the way I've had to in the past. I thought the points were getting corroded from sitting. Now I think they were pitting from breaking too much current.
I've seen brand new points burn out in as little as a half hours running a 6 volt coil on 12 volts. (Have also seen a coil overheat and split open...).

With the ballast resistor your THD's points should now last a LONG time!
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