# Yamaha YT3600 electrical problem



## hardway (Jul 23, 2011)

Have a Yamaha YT3600 lawn tractor. The battery is good but mower will not recharge the battery. replaced battery anyway and have the same problem. my knowledge of the electrical system on this lawn tractor very limited. Something is draining the battery. Running the mower does not keep battery charged. The battery is needed for the PTO. Sounds like a alternator type issue or what ever these systems use to keep battery charged. I understand the PTO needs the battery to function so i am assuming that drains the battery the quickest. any ideas or troubleshooting ideas would be great.! thanks


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## jjkrug (Aug 1, 2011)

I have a YT3600 also that had the same problem. It was the alternator control unit. I bought the part from Speed and Sport in Bloomsburg, PA. It was about $120 as I recall. 

They also carry the service manual. You should definitely invest in the manual before throwing parts at the machine.


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## StewartRobbins (Sep 23, 2019)

I have the same problem. It appears Speed and Sport need a part number. Any ideas on that? They aren't seeing anything regarding an alternator control unit. Part number for the service manual would be great too.


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## Bob Driver (Nov 1, 2017)

I believe Yamaha used what they called a "Charge Coil" on those engines that fed through a rectifier/regulator.
*Charge coil* -- Part # JA1-85520-00-00. Item # 1 in the link below
partsfinder.onlinemicrofiche.com/yamahagenuineparts/showmodel.asp?Type=13&make=yamahaope&a=191&b=26&c=0&d=1900%20YT3600M%20GENERATOR
*Rectifier/Regulator* -- Part #1JK-81960-A1-00. Item #6 in the link below
partsfinder.onlinemicrofiche.com/yamahagenuineparts/showmodel.asp?Type=13&make=yamahaope&a=191&b=26&c=0&d=1900%20YT3600M%20GENERATOR

Those are some pricey parts ($112 for the coil - $207 for the rectifier) for a 27 to 31 year old mower. The problem could be either one, or both. That charge coil is going to put out *A/C voltage* that is turned into 12v DC by the Rectifier/Regulator. Don't know a spec for how much on the A/C voltage output, but both Briggs & Kohler are 28v minimum at full throttle

Find what looks like that Rectifier/Regulator. Use a multimeter on A/C to see if you're getting an A/C reading coming into the rectifier from the charge coil(red at the input lead(s) coming from the charge coil, black to ground). No reading.. No A/C output to the rectifier- bad charge coil. If you get 28v(?) minimum A/C output at full throttle -- bad rectifier.

Most commonly DC voltage leaves the rectifier/regulator and goes to the key switch. With the key in the RUN position, it supplies 12V DC to charge the battery through internal contact between the B terminal (battery) and the A terminal (alternator) at the key. Trace the output wire up from the rectifier/regulator and see if it goes to the key (there is usually a diode in that wire to prevent feedback from the battery to the rectifier)…. If you're really, really, lucky it could be a bad key switch (no contact between A&B terminals), or a diode that is burnt out and breaking contact in the wire bringing 12V DC up to the A terminal at the key from the rectifier/regulator


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## StewartRobbins (Sep 23, 2019)

Bob, I can't thank you enough for the info on this. I'll get some troubleshooting done and report back. Thanks again!


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## Bob Driver (Nov 1, 2017)

Apparently Yamaha exported a lot of those to Europe. Here's a link to a Dutch website that is really good for motorcycle parts, but they also list the YT3600
https://www.cmsnl.com/yamaha-yt3600_model16703/

The Service Manual is out there online, but good luck finding it for free on something that old. Part # for internet search is JA1281997200. Here's a link to download a PDF manual for $50 CAD
https://www.yamahagenuineparts.com/powerproduct/moreinfo.php?ID=3&shopcat=shop


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