# Craftsman Mower PTO Harness Diode



## John Lolli (Nov 3, 2005)

I have a Craftsman DYT4000 mower 917-273642. It was blowing the 20 amp fuse when I turned on the PTO. I have traced the problem to the diode in the PTO harness on the engine side. The diode melted and broke in half and burned off the insulation on the red wire from the PTO switch and caused a dead short. I need to replace the diode. What kind of diode do I need and where can I get one. Is there anything else I could do to fix this.


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## dawgpile (Apr 28, 2008)

I looked at the manual for your mower and it states it has a 9amp charging system. You can buy diodes rated for 10A very inexpensively on ebay. I just saw a post for 10 pieces for 6.95 w/ free shipping and that's from here in the states. One of these will do the job. Don't worry that is says it's rated for 1000V (1000 peak inverse volts). In this case, the current is important.

Radio Shack carries a 3 pack of 6 amp diodes, but I'm afraid this will be a little light. Don't let anyone tell you that all you need to do is put two of the 6 amp ones in parallel. NOT TRUE. Without going into an electrical engineering lesson which I'm sure you could care less, suffice it to say, the better approach is to use ONE that is sized larger. You could buy from a parts place like Mouser or DigiKey but you'll certainly pay more!

Good luck!

(if anyone wants to know why you can't parallel the 6a diodes to 'share' the current and effectively handle 12a, I'd be happy to explain)


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## 30yearTech (Sep 14, 2006)

dawgpile said:


> I looked at the manual for your mower and it states it has a 9amp charging system.


The diode I believe he is referring to is in the PTO circuit not the charging circuit. When I looked at the wiring diagram I see a diode to the electric clutch, but no listing or rating for it in the parts IPL.


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## John Lolli (Nov 3, 2005)

Thank you all for your replies. This is the diode I installed in the circuit. OEM KOHLER CLAMPING DIODE KIT PART# 25-755-40-S


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## dawgpile (Apr 28, 2008)

John, 30yr is absolutely correct. I did some more checking and it turns out this diode is a 'snubber' diode which is placed across the PTO coil. Its purpose is to absorb the energy spike produced when you suddenly interrupt the current to the PTO coil(when you disengage the blades). While the PTO will work just fine without the diode, the PTO switch will fail prematurely from the arcing and sparking produced. That's why it's needed. 

What you purchased is a 6A diode and should do the job just fine. Keep in mind the polarity matters. Make sure to connect the banded(cathode) and unbanded(anode) ends of the diode the same as the old one. If you don't know how the old one was connected because it's fried, the unbanded anode end connects to the grounded side of the PTO clutch, and the banded cathode end connects to the switched side of the PTO clutch which connects to 12Volts.

BTW, you'll know if you have it connected backwards as it becomes a dead short and either it and/or the fuse will blow when you hit the PTO switch!

Good Luck!

Kelly


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## John Lolli (Nov 3, 2005)

The Kohler diode actually had red and black wires already connected plus instructions and connectors. All I had to do was splice into the existing wiring. They make it real easy. Everything working fine. The diode kit was $10. I thought it was worth it since they made it so easy and also rugged.


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