CV16S alternator test

PTmowerMech

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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..


20200310_124145.jpg
 

StarTech

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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.
 

PTmowerMech

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You mean like this?

Meter on battery
20200310_133114.jpg

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

20200310_133207.jpg

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.
 

StarTech

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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.
 

PTmowerMech

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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.

1583879719308.png
 
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StarTech

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Check your email inbox...
 

Rivets

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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.
 

StarTech

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

PTmowerMech

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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.

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.
 

PTmowerMech

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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.
 
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