# Briggs/Kohler swap - charging issue



## trehahn (Jun 29, 2012)

We have a New Holland LS 55H mower which had a Kohler engine on it, and was blown up. The guy who owned it, put a 20HP Briggs and Straton Husky twin cylinder on it but now it doesn't charge. It appears to me, the Briggs has a different charging system than the Kohler did, which is probably the cause. 

The Briggs has 3 wires coming out, a rectangle connector with a Red/black which plugs into Red/white and a yellow single wire. I'm not sure what the Kohler had, but a quick search it appears the Kohler was an AC output, and the Briggs appears to be a dual circuit. 

The Briggs that has a model number of 460777 though I couldn't find much on it.


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## Basementgeek (Feb 7, 2005)

Hi and welcome to TSF

It looks like B&S had about 7 different alternators for that size engine.

Check the voltage on each of the two pins to ground. One could be AC and other one DC. The AC would be used to run the headlights. DC would go the battery.

BG


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## MrChooks (Apr 19, 2008)

See if this helps you sort out the wiring - Note there may actually be 2 alternator systems in the one unit - one AC for lights and another independent DC for battery charge


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## trehahn (Jun 29, 2012)

I tried checking the voltage, but it kept jumping around like a slot machine, no numbers stayed the same, and it went up over 100 volts, it was 3 digit numbers with 1 decimal. No matter which pin, which setting (AC/DC) it did it. 

I just went through a charging issue with a Craftsman nobody could find the short and why it wouldn't charge. I found the short was going to the alternator, and traced it back to the diode assembly bad, allowing DC voltage back through it. I also measured the voltage and current to make sure it was charging. It had another issue with the electric clutch kicking in, killing the engine, which is why the guy sold it for $50 he couldn't get anyone to figure it out, I did. This one baffles me. I have an electronics background, but the readings this mower gave were whacko!


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## MrChooks (Apr 19, 2008)

So have you got it fixed?? - sort of sounds like you have it nailed and all is good. In which case you have a winner @ $50 for the mower :dance:


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## Basementgeek (Feb 7, 2005)

You measured each pin to ground, correct? 2 pins, 1 AC, 1 DC my guess.

BG


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## trehahn (Jun 29, 2012)

No I didn't get it fixed, I was mentioning a Craftsman I just traced down for my Dad, just so everyone gets an idea of my knowledge on the situation, that I know my way around a meter, etc. 


The answer to the question, yes I measured each pin to ground, both just went crazy. When it was off, I was able to check resistance, but voltage just went nuts.


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## Basementgeek (Feb 7, 2005)

Maybe attach something to use as a load on the circuits? Just guessing here as I have no clue.

BG


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## MrChooks (Apr 19, 2008)

I am a bit like yourself and BG here - clutching at straws as to what is the problem.

The one issue that has me thinking was the weird 100V+ test results you got. I am no expert on alternators BUT these voltages are way out and I am suspecting the voltage regulator within the alternator circuit maybe shot. Being a 12V system - the read outs you got should have been about 14V+/- and nowhere near 100V+/-.

In the old days the voltage regulators were a mechanical relay that clicked in and out to control the volatge within the rotor and hence the induced volatge within the field (I think- but not absolutely certain). Modern alternators use solid state / electronic switching to do this - either way the output voltages should be about 14V +/-.

If the voltage regulator is solid state and built into the alternator - my guess is you will need a new one - but maybe you can find / ask a "friendly" auto electrican who could advise you if your alternator is fixable


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## MrChooks (Apr 19, 2008)

I just found something that might give you some help here - its a 52 page B&S manual on their alternators and set-ups which just might give you some clues on what to do next - 

Have a look at this link & see comments / issues on page 21 regarding engine swaps and what connection changes will be needed

http://www4.briggsandstratton.com/miscpdfs/RNT/alternator_replacement.pdf


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## trehahn (Jun 29, 2012)

Thank you guys so much for all the help. I still think it's an incompatible wiring harness that's causing it. Possibly much like the old Craftsman I diagnosed a couple weeks ago, it probably has a diode assembly up the harness more, but we can't see it because it's all enclosed. That would block the DC from getting through, since the Briggs has the diode right in the harness coming out of the engine, along with the AC wire. I'm thinking I may have to just wire it myself. 

I'm still baffled by the erratic reading, and will have to check it again. The tractor was taken to my Aunts house, she wanted it and we were going up there this weekend, I had the trailer etc. So we'll have to get up there to check/fix it, for now she's just going to charge the battery. I would have preferred to wait, but well they're older and wiser LOL 

I do appreciate all the help, and MrChooks that file does have some great info. I have a file similar, but did not see that information in it, I'm certainly going to keep that file for later use! Thank you again!


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