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Scotts 1642H with Kohler CV16S Spec 43526
The colors are a little hard to see (yellow vs white) But the yellow one comes out of the harness and goes up beside the diode.
With the engine reved up and my meter on the AC selection, pos to yellow & neg. to the engine block, I get the same reading as the battery has. I should be getting a lot more than that, right? Or am I not testing it right?


BTW, the diode, with the meter on the diode selection, I get about 5 one way and nothing (OL) when I swap sides with the leads..

Diodes usually are tested with your meter's diode test mode. 0.7 forward and OL in reverse for silicon diodes. This is the voltage drop across the anode/cathode junction. The cathode is the side with the black band.

The yellow is AC for the lights and not for your battery (13Vac or more). The lead with the diode (half wave rectifier) is the battery charge wire. If voltage is more than 12.5 volts DC, charging system is OK.
If voltage is 13.8-14.7 DC and charge rate increases when load is applied, the charging system is OK and battery was fully charged. Note this is at 3400 rpm.

White lead is the magneto kill. The red leads are to the speed advance module and fuel solenoid if I remember correctly.

You mean like this?

Meter on battery


Meter on black wire, at full throttle. I don't have an RPM gauge. But it's revved up pretty high.



I still have my meter on it, with it not running. Maybe there's a short that's draining the battery, somewhere.

God I hope not.

Batteries develop a surface while charging that slowly dissipates as it sits back down to 12+ DCV overnight. Usually between 12 and 13 is normal. As note this surface charge is being higher than the normal battery voltage is perfectly normal. What you don't want is to be charging the battery over 16 VDC.

You know how Craftsman and a lot of other mowers have that charging wire connected to the POS battery wire, This one has it. But that's not something John Deere does, is it? I don't think it's original.
One end connects to the POS wire from the battery to solenoid. The other end goes to the B on the key switch. When it's running, I'm getting about 26v from it. With the engine off, I get nothing.

Now here's the kicker. The engine won't turn over with these two wires disconnected.
So now I'm thinking safety switch, except the seat switch is wired in original. THE only thing that's not original is the POS battery wire, with the charging wire that's connected to it. And, seems that small charging wire has been spliced to fit the connection for the wire from the B on the key switch.

So after a bit of deductions, where is the other end of that connection supposed to go. Because it's obviously not supposed to go back to the POS battery cable. Is it?

B on Key switch, Red wire to -----------fuse----------------to connector off of the POS battery wire at solenoid.

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Careful checking diodes while they are still connected in the circuit, you may get a false reading. I always remove one lead from the circuit before testing.

Your right I do forget sometimes as it is automatic with me after 40 yrs.

Rivets said:

Careful checking diodes while they are still connected in the circuit, you may get a false reading. I always remove one lead from the circuit before testing.

Click to expand...

Remove one lead? Meter lead?

I had the harness disconnected when check it.

Didn't I? I think I did. ... No, I know I did.



Crap, I'll check it again............


It's good.

I put a different battery on it, mowed for about 10 minutes. The battery, with engine off (7:00pm) is at 12.90v). If it's dead in the morning, I'll have to start all over.

When it is nice & dark go pull one battery lead off.
If you get a spark then there is a load on the battery which is flattening the battery.
Most of the modern rectifier / regulators are always on so will put a tiny load.
If the beck feed diode has gone then overnight the alternator tries to be an electric motor ( electrically they are one & the same ) which will draw down the battery .
I leave mower out overnight , hood up
No dew on the blower husing or hosing warmer than the rest of the mower indicates rectifier failure.

Take a cable off the battery, hook it in series with a small 12v light bulb, look for any glow. Should be no drain on it. Does your multimeter have an amp/milliamp setting? Might check with that if so.

Parasitic draw. Charge the battery. Set meter to AMPS and connect the meter leads between the + batt terminal and the batt cable. All current will flow through the meter. Do NOT turn the key on or try to start the mower. Will blow meter fuse.
If there is a parasitic draw it will show on the meter. Disconnect the voltage regulator and see if the meter goes to zero, if so check the diode or suspect the regulator. Is there is still current flow after disconnecting the VR then something wired wrong or shorted.

bertsmobile1 said:

When it is nice & dark go pull one battery lead off.
If you get a spark then there is a load on the battery which is flattening the battery.
Most of the modern rectifier / regulators are always on so will put a tiny load.
If the beck feed diode has gone then overnight the alternator tries to be an electric motor ( electrically they are one & the same ) which will draw down the battery .
I leave mower out overnight , hood up
No dew on the blower husing or hosing warmer than the rest of the mower indicates rectifier failure.

Click to expand...

This mower doesn't have a rectifier or regulator.

One of those goofey 3 amp unregulated charging systems?

PTmowerMech said:

This mower doesn't have a rectifier or regulator.

Click to expand...

Wait one dang blame minute here. It does have a rectifier, that what the diode is. Diode and rectifier are interchangeable terms. Now there are different types for special purpose like a zener diode which are voltage regulators. It is right there that we been talking about checking in the image posted. It is high temperature SOD-57 case Silicon 3 amp diode. Can be replaced with a 1N5408-G diode 1000V 3 amp axial lead case 267-05 style 1.

Hammermechanicman said:

One of those goofey 3 amp unregulated charging systems?

Click to expand...

And yes it a 3-5 amp unregulated system. Luckily here that it don't also have stator brake winding.

tom3 said:

Take a cable off the battery, hook it in series with a small 12v light bulb, look for any glow. Should be no drain on it. Does your multimeter have an amp/milliamp setting? Might check with that if so.

Click to expand...

Most meters will only go to 10 amps and that is an unfused test mode so if there more 10 amps draw you will fry your meter. Uae this mode only if you know for sure the circuit is drawing less than 10 amps. Use 40/400 amp clamp type amp meter or similar meter adapter. And yes that diode can be leaky.

PTmowerMech said:

I put a different battery on it, mowed for about 10 minutes. The battery, with engine off (7:00pm) is at 12.90v). If it's dead in the morning, I'll have to start all over.

Click to expand...

Now, at 9:30am, the next morning, I'm at 12.76. A .14 drop, just from sitting. That's a lot better than it was. Yesterday it would've dropped that much in an 1/2 hour. All I really did, yesterday, besides checking current, was swapped a ground wire from the top to the bottom of another one.

One thing I did before I finished for the day yesterday, was check the continuity from the +POS side of the battery to the engine on this one, and a few others. All of them were 042 to 045. I don't have a clue as to why. But they all read that.

bertsmobile1 said:

When it is nice & dark go pull one battery lead off.
If you get a spark then there is a load on the battery which is flattening the battery.
Most of the modern rectifier / regulators are always on so will put a tiny load.
If the beck feed diode has gone then overnight the alternator tries to be an electric motor ( electrically they are one & the same ) which will draw down the battery .
I leave mower out overnight , hood up
No dew on the blower husing or hosing warmer than the rest of the mower indicates rectifier failure.

Click to expand...

I just tried this and didn't see any kind of a spark. I didn't read this til this morning, so I didn't try the dew trick. The batter did drop about .14 in 14 hours. Which isn't much. But being left for a week, I'm sure it'll be a problem.

@2:30 this afternoon, it's still at 12:76.

All I did was unwrap, check and rewrap the diode. Remove a ground bolt, putting the bottom wire on top and re-tightened it.