Kohler charging

Bret4207

Well-known Member
I have an AC 312H w/Kohler 301. It's never charged. I replaced the rectifier some years back and replaced stator yesterday. NO charge. How do I test this system? Can I test the stator while running? It could just be a bad wire in the rats nest behind the tank, but there should be a way to check power before the amp meter.
 

My book shows five different charging systems used on the K series engines: 1.25, 3.0, 10, 15 and 30 amp. The 1.25 and 3.0 amp systems are un-regulated and will have one lead from the stator. The 3.0 amp system may have a lighting option in which case there is a yellow lead for lighting. The 10 and 15 amp systems are regulated and will have two leads from the stator. The 30 amp system has four leads from the stator.

I am guessing you have a 10 or 15 amp system in which case the two stator leads go to the "AC" terminals on the rectifier/regulator. The "B" terminal on the rectifier/regulator is connected to key switch which connects to the ammeter which connects to the battery side of the starter relay which connects to the battery (+) terminal.

With the engine running, you should see AC voltage across the two "AC" terminals on the rectifier/regulator. You should see DC voltage across the "B" terminal on the rectifier/regulator to chassis (ground). From here simply follow the DC voltage to the switch, ammeter, starter relay and finally to the battery.

Note: 1) The DC charging voltage is routed through the key switch. Have found the switch to be a problem. At 10 to 15 amps the switch contacts and or terminal connections can fail.
2) My engine is rubber mounted and has a ground strap from the engine to chassis...also verify the regulator/rectifier case is grounded to it's mounting point on the engine.
 


Thanks guys. I finally found my Kohler manual, which was right where I'd left it as usual, but no where near where I remembered leaving it! I have about 32 volts AC across the stator leads (15 amp system. I have nothing out of the rectifier, which the book indicates means it's bad. I just replaced the old rectifier a few years back and it never worked, which was why I replaced the stator recently. I don't know why the new rectifier would go bad. The part# I have is 1604532 which appears to be obsolete now. Will any 15 amp Kohler rectifier work? The stator leads appear to go to AC/AC and the lead out is B+, 12v DC I assume. I don't know/am unclear if the B+ lead will always show 12v.
 
If connected directly to the battery the B+ lead will always show battery voltage.

However, often garden tractor wiring is set up so that the ignition switch disconnects the battery from the regulator when the ignition switch is "OFF".

It would depend upon which way yours is set up.
 

Thanks Bob. I have zero volts AC or DC out of the B+ lead when connected to pos side of batt. Should be a bad rectifier then?

ETA- IIRC when I touch the B+ it indicates a dead ground. Must be shorted inside.
 
(quoted from post at 11:25:13 05/02/16)
Thanks Bob. I have zero volts AC or DC out of the B+ lead when connected to pos side of batt. Should be a bad rectifier then?

ETA- IIRC when I touch the B+ it indicates a dead ground. Must be shorted inside.

In reply to your first paragraph: How are you connecting your VOM leads? With the engine running, the positive lead on terminal "B" and the negative lead connected to ground, you should read at least battery voltage (not charging) or greater than battery voltage (charging).

In reply to your second paragraph: If Terminal "B" was grounded then the battery would fry the wiring as soon as the key switch was turned on - direct battery short to ground. The case of the rectifier/regulator must be grounded but not terminal "B".

I would suggest you verify you have an electrical path from terminal "B" to the battery (+) terminal as follows: With the engine not running remove the wire from terminal "B" and meassure the voltage from the [u:5dc4d6d05b]wire[/u:5dc4d6d05b] terminal to ground. It should read zero since the key switch is off. Now turn the key switch on - you should read battery voltage. If you still read zero volts there is a bad connection, broken wire, bad switch etc.
 
(quoted from post at 16:40:45 05/02/16)
(quoted from post at 11:25:13 05/02/16)
Thanks Bob. I have zero volts AC or DC out of the B+ lead when connected to pos side of batt. Should be a bad rectifier then?

ETA- IIRC when I touch the B+ it indicates a dead ground. Must be shorted inside.

In reply to your first paragraph: How are you connecting your VOM leads? With the engine running, the positive lead on terminal "B" and the negative lead connected to ground, you should read at least battery voltage (not charging) or greater than battery voltage (charging).

[b:a93f5b17e5]Ken, IIRC the 2 stator leads show 32 volts AC when connected
to the multimeter and one lead shows the same voltage when connected to ground.
[/b:a93f5b17e5]

In reply to your second paragraph: If Terminal "B" was grounded then the battery would fry the wiring as soon as the key switch was turned on - direct battery short to ground. The case of the rectifier/regulator must be grounded but not terminal "B".

I would suggest you verify you have an electrical path from terminal "B" to the battery (+) terminal as follows: With the engine not running remove the wire from terminal "B" and meassure the voltage from the [u:a93f5b17e5]wire[/u:a93f5b17e5] terminal to ground. It should read zero since the key switch is off. Now turn the key switch on - you should read battery voltage. If you still read zero volts there is a bad connection, broken wire, bad switch etc.
b]

I just went and checked the B wiring as you stated. With the key off, I get no voltage between the wire going to B and ground. With key on I get several volts but the meter indicates it's a reversed (positive) ground. I'm thinking I'd better check my wiring.

Thanks for taking the time and effort to help me try and figure this out.
 

Sounds like you are making progress. The stator leads are not grounded so I don't understand how you can have 32 volts from one lead, I will ignore this for now. 32 volts AC with the stator leads connected directly to VOM (un-regulated) sounds about right.

A simple way to check the wiring to the battery is to run a jumper from the "B" terminal directly to the battery (+) terminal. The negative terminal of the battery must be connected to chassis (ground). With the engine running and the jumper connected the VOM should show an increase in battery voltage - indicating charging.

Note: You should be using a fully charged battery to check for charging voltage. I have never tried to run a Kohler without a battery but I have found some other charging systems that require a battery to trigger the regulator/rectifier before outputing a charging voltage.
 

UPDATE- Figured it out. There was nothing wrong with rectifier/stator I think. It's a wiring issue. On Kens advice I ran a wire directly from B spade to Pos side of battery and watched the voltage rise from 12.8 to over 14v! Tested by engaging electric clutch and implement lift. Comes back up to 14+ every time. I'm going to pull the tank and trace the wires. Also going to go to something heavier than 16ga wire! It was definitely warm when testing.

Thanks to all who helped! :D
 

Got the tank off. Turns out the switch is bad. I tore it apart and cleaned it's innards, but still no joy. Also found out the ammeter is busted, only works a little in one direction. But I fixed a bunch of wiring and rigged a switch to charge for now.

Thanks again!
 

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