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Riding Lawn Mower will not Charge Battery

12374 Views 1 Reply 2 Participants Last post by  Mark / Ohio
Craftsman DYT 4000
Model No. 917.274033
21.0 HP Briggs and Stratton
Intek 21V Twin
42" Mower

New to this forum. So my battery died. My dad went to buy a new battery at the auto part store. Well they sold him the wrong battery. The neg and pos were on the opposite sides. My dad not looking at the battery, connected the battery incorrectly.

After getting a new correct battery, it looks like he blew a fuse. Changed the fuse out. Now it looks like the Lawn Mower is not charging the battery. With a full battery charged, it looks like the Voltage is 12.54 on my Voltage Meter. When I start the lawn mower and turn on the blades, the Voltage still reads 12.54 and drops very slowly, maybe .01 volts every 30 seconds.

1 hour into mowing the lawn, the Blades will not turn anymore. The lawn motor will still run, but the blades will not turn. From what I read, the Battery is what runs the motor that turns the blades.

I've troubleshoot it down to the Voltage Regulator or Diode. Looked at the Sears site and the Voltage Reg is like ~$75.00. They don't sale the Diode just the wire with the diode on it, ~$45.00. Most likely I think its the diode. Can I just buy a diode and solder it on? What size or what kind of diode is this?

Is there a way to test the Voltage Regulator or Diode to see who causing the issue?

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...Is there a way to test the Voltage Regulator or Diode to see who causing the issue?

Using resistance (ohm) meter, bad diodes normally either short (0 ohms) or read open (infinity). Most meters that read resistance have a diode check feature on them. Hooking the meter leads in one direction on the diode it will read a different resistance then when you reverse the lead polarity to the opposite direction on a good diode. Sometimes diodes can read fine with a meter but once the larger voltage and current hit them they open up. Regulators can be even a little more tricky. The diagram I found at Sears must be sort of a generic one. It does not show the diode outside of the regulator.

What you can do is try to verify the AC output of the alternator, then verify with your voltmeter the DC output of the diode to the regulator. If you have power into the regulator then it is probably a bad regulator. On the input side of the regulator (output of the diode) you should see a change in voltage versus engine rpm.

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