# Battery not charging from magneto



## gmcchamp99 (Oct 18, 2015)

So i have a OHV150-204034E OHV15A Tecumseh engine that i retrofitted into a 70's sears tractor. Runs great but cant charge the battery as the voltage that comes out of the magneto is 14-19V depending on the engine rpm. My question is obviously tecumseh is belly up and everywhere ive called, this voltage regulator is unavailable. Anyone know of any other type of regulator i could use to make this engine able to charge the battery? I know for a fact it has more than enough voltage, i just need a regulator. 

Thanks,


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## jhngardner367 (Apr 5, 2011)

Use one from a Kohler ,they should be about the same .


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## gmcchamp99 (Oct 18, 2015)

Thanks jhngardner367! Should i purchase one from an engine of the same CC Size? 15hp? or a specific model.


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## jhngardner367 (Apr 5, 2011)

No need to .
you should be able to find one on Amazon.com...,or Ebay,pretty reasonable
Or you can get one from a dealer(but it's more expensive) !
As long as they look the same,with the same connections,it should work.

Meant to ask you,...when you say the voltage out of the alternator is 14-19v,which tabs are you checking?
Generally the center tab is DCvolts,for the battery.
The 2 outer ones should read about 30 Volts AC.
Connect one lead of the voltmeter to one outer tab,and the other lead to the other outer tab,with the engine a full throttle .
When you check the center tab,connect the black voltmeter lead to ground,and the red to the center tab.
It should read 13.7- 14.9 volts DC.


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## Bill Kapaun (May 8, 2007)

Just exactly what are you measuring?
The voltage between 2 wires for a system with a Voltage Regulator OR the voltage from 1 wire to ground for the system with a charge diode?

I've never seen a system using a VR that 19 VAC input is sufficient. Most need at least 28 VAC.


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## jhngardner367 (Apr 5, 2011)

That's why I mentioned measuring the 3 connectors,from the alternator.
AC volts between the 2 outside connectors, and Dc for the middle connector and ground.


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## Bill Kapaun (May 8, 2007)

I suspect he has a 3 Amp charging system with AC lighting circuit.
Thus my question about HOW was it measured.

"....the voltage that comes out of the magneto is 14-19V depending on the engine rpm.... ....I know for a fact it has more than enough voltage, i just need a regulator...."

There MIGHT be a TEC charging system where 14-19V is OK, but MOST TEC charging systems require more.
IDENTIFYING WHICH system the OP has MIGHT save a lot of time.
Wire COLORS would help.


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## gmcchamp99 (Oct 18, 2015)

So at full throttle, the yellow wire coming out of the engine puts out 19V. There is another wire that comes out that is red and that only has 4 volts and looks as if it may have a diode attached. 
The third wire that is on the engine is the green wire that goes to my ignition switch so that i can shut the engine down by the key.


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## Bill Kapaun (May 8, 2007)

This circuit DOES NOT use a Voltage Regulator-

The Yellow wire is your AC lighting circuit.
The RED is your charge wire.
It should be ACV on the alternator side and pulsating DC on the battery side of the DIODE.
The DIODE simply works like a check valve, allowing the + part of the AC Sine Wave through, but blocking the - part of the Sine Wave.

Set your meter to AC or DC as appropriate.

A quick test on the RED wire would be connecting a 12V bulb (like an automotive back up/tail light) to see if it lights. That won't tell if you have AC or DC, but should tell you if the alternator is "working".

The diode can be tested with the OHMS function of the meter.
It should show conductance in one direction and NOT in the other direction.
(swap test leads)
You may have to try a couple different scales on the OHMS to get one that is correct.
No conductance either way, DIODE is OPEN.
Conductance both ways, DIODE is shorted.


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## Bill Kapaun (May 8, 2007)

For a Service Manual, GOOGLE-
695244a

You'll find a pdf download-
https://www.google.com/url?sa=t&rct...bF-UNW5LWw3FIAjvpKcYwg&bvm=bv.139782543,d.cGc

Look at page 47/94 for your system.
3A DC/5A AC


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## jhngardner367 (Apr 5, 2011)

Yep , Bill, you nailed it!
First post made it sound like it had a reg/rec,and it shows one available.


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## Bill Kapaun (May 8, 2007)

When looking at the service manual, I was surprised at the number of configurations of charging systems that Tec used.

Now, if we knew the Sears 917.xxxxxx number of the tractor, we could see if this charging system is appropriate for this tractor, or if electrical "surgery" is required to the wiring harness.
Hopefully, the OP doesn't have an electric PTO, if he wants to charge the battery while mowing.


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## gmcchamp99 (Oct 18, 2015)

Ok. So the yellow wire that at high rpm pushing 19 volts is to power the lighting circut. The red wire pushing 4 volts that has th3 diode on it gets directly wired to the battery which at 4 volts it will charge? I'll give it a try tomorrow when I get home and report back the results.


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## Bill Kapaun (May 8, 2007)

I don't know if the RED wire goes directly to the battery or the Key Switch.
KS is more likely.
Since you don't want to provide the Sears tractor #, one can't look at a CORRECT schematic.

I'd suggest at least looking at the service manual and follow their tests.

You don't even mention if you are measuring AC or DC.
Details MATTER!


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## gmcchamp99 (Oct 18, 2015)

The sears tractor model wont do you any good as this motor is not the original motor to the tractor. The sears model is 131.96972 which was equipped with a 8hp Tecumseh. I ll check if the voltages are AC or DC. I don't know off hand as my fluke voltage tester is auto sense and you dont need to change settings to go from AC to DC or vice versa


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## Bill Kapaun (May 8, 2007)

"I know for a fact it has more than enough voltage, i just need a regulator."
And you have no clue if it's AC or DC.

"The sears tractor model wont do you any good as this motor is not the original motor to the tractor."
It tells me if it has headlights or an electric PTO.

I guess trying to help you won't do me any good either.


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## gmcchamp99 (Oct 18, 2015)

Help is at will with no barrels pressed at anyone's temple. If helping me wont do you any good, by all means continue past this thread to the next one. The info is incomplete as I was out of town for the holiday and just got back this evening. Being inexperienced with the electrical system of this tractor i came here to seek info with limited info before hand.

The red wire puts out AC voltage before the diode and DC out after it. Yellow wire puts out AC voltage. Since the ignition I have doesn't accommodate the wiring through the switch itself so my educated guess would be that it get wired through the ammeter then to the battery. The yellow wire will be wired through the switch assembly for the lights and power that circuit.


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