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Working on a friends mower. A couple of days ago it quit on him after he stopped it to move something. It would not crank.
He (not mechanically inclined) brought it over and and I found a blown 20 amp fuse under the seat.
He went and got some fuses and proceeded to mow again and it did the same thing after about 5 minutes only this time when he put the new fuse in it blew immediately.

Fast forward to today. Using a VOM I found a dead short on the fused wire. After reading a bit, I disconnected both connectors to the engine, the short disappeared.
Plugged the connector to the key switch in... no short. Plugged the connector to the engine and the short reappears.

I unplugged the voltage rectifier/regulator and the short disappeared, put a fuse in the holder and no short. Hooked the rectifier/regulator back up and the fuse blew immediately,
I believe even before I ground the regulator.

Using a VOM none of the lugs on the rectifier are shorted to the case. Terminal B+ to AC shows a short (continuity), Terminal B+ to O DOES NOT show a short (continuity), Terminal AC to O DOES NOT
show a short (continuity).

I am assuming the rectifier is bad but don't know. Can the AC & B+ short together and be causing the short circuit or do you think I need to look into the Stator as the possible culprit?
If so is there a test procedure to check it before I have to take the flywheel off?

All help would be appreciated.

You can do continuity between the two stator wires and get a resistance reading which should be low. then connect to either one of the AC wires on the stator and the engine block and if you have continuity then the stator is shorted. Also depending on style of charging system the 15 amp regulator on some engines is only half wave rectified, so could have continuity from the B+ through the AC and if the stator is shorted could be your short to ground.

Another question........ If I remember correctly and I will verify in the morning, the B+ wire coming had voltage going to it with the key switch in the off position.
Am I right in assuming it should only show battery voltage when the key if turned on and not have continuous power at all times?

If that's the case is it possible the key switch is defective and causing the problem instead of the rectifier or the stator?

Depends upon which rectifier is fitted .
Some draw a tiny current 24/7 while others draw none
Some ignition systems ground out the alternator to turn it into a vary inefficient electric motor in order to stop the engine quickly .
While all mower wiring is basically the same there are quite a few variations.
Not uncommon to find the rectifier wire hooked into the battery feed wire to the ignition switch and even worse often after the fuse .

bertsmobile1 said:

Depends upon which rectifier is fitted .
Some draw a tiny current 24/7 while others draw none
Some ignition systems ground out the alternator to turn it into a vary inefficient electric motor in order to stop the engine quickly .
While all mower wiring is basically the same there are quite a few variations.
Not uncommon to find the rectifier wire hooked into the battery feed wire to the ignition switch and even worse often after the fuse .

Click to expand...

The number on the rectifier is 25 403 35 4215

Shootertexas said:

Another question........ If I remember correctly and I will verify in the morning, the B+ wire coming had voltage going to it with the key switch in the off position.
Am I right in assuming it should only show battery voltage when the key if turned on and not have continuous power at all times?

If that's the case is it possible the key switch is defective and causing the problem instead of the rectifier or the stator?

Click to expand...

Depending on how the system is wires. Having battery voltage at the B+ terminal is normal in most cases and is the preferred method by Kohler. Some mower manufacturers will wire it through the key switch, but in a lot of those cases there is also an amp meter on the dash, and the system won't work with an amp meter if the regulator is wired directly to battery power.

XT1-LT50 RIDER

I think Kohler just gave me something to research. I place an order this coming week to verify my suspicions. I may need to add an internal supersede to my system.

I noticed my VOM was acting flaky so I got my other one and retested
So far with rectifier removed and engine running:
Stator output test = 21v +/- at idle 30v +/- at WOT
Stator leads to ground do not show the stator to be shorted on either lead.

On a whim, I rechecked the rectifier on one AC leg to ground I'm getting 43.3 ohms, on the B+ to ground I'm also getting 43.3 ohm and the other AC leg I am getting nothing. On the AC leg that was showing 43.3 ohms to the B+ leg on the rectifier, it is showing continuity.

Is the rectifier shorted internally?

The test on the stator show it to be good. I suspect the regulator is shorted, and with those ohm readings would have more parasitic battery drain that considered normal.

Is it 43.3 ohms or is it 43.3 k ohms? Also using diode check mode on your meter do you get anything from B+ to the case ground.

StarTech said:

Is it 43.3 ohms or is it 43.3 k ohms? Also using diode check mode on your meter do you get anything from B+ to the case ground.

Click to expand...

43.3k ohms. B+ to case shows 43.3K and one of the AC lugs also shows 43.3k both to case ground. Between the two lugs that shows the 43.3 it reads 0.00k.

Then is a fairly normal reading using regular resistance check. Those two terminals are probably center and the RH one with terminal facing you. Do diode check between any of the three terminals and the case, they should be register "OL" Both forward and reverse.

Or at least the two regulators here checks this way and they are new, never installed yet.

StarTech said:

Then is a fairly normal reading using regular resistance check. Those two terminals are probably center and the RH one with terminal facing you. Do diode check between any of the three terminals and the case, they should be register "OL" Both forward and reverse.

Or at least the two regulators here checks this way and they are new, never installed yet.

Click to expand...

With the terminals facing me it is the left and center.
I did a diode check and you are correct, I get a 1 (all three of my meters use 1 instead of OL) both forward and reverse.
Don't know if it matters but with the + lead on B+ and the AC to the left, I get a reading of .021, reversing the wires I get .033.

I'm just at a loss as to why if everything is hooked up, it will blow the fuse as soon as it is put in the holder but with the rectifier unplugged it will not blow the fuse and will start and run.
Maybe I missed a short in the purple wire, key switch or something. I'll check again in the morning.

If it works without the regulator connected, but blows the fuse as soon as it is connected I would say the regulator is shorted, and needs to be replaced.

Thanks guys. Replaced the rectifier/regulator and it lives. Checked the volatge at WOT @ battery and it showed about 14.5 +/- volts.

It appears now there is a much bigger issue but not with the regulator or charging system. Seeming unrelated but who knows.