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Small Engines (Lawn Mowers, etc.)/melted wire from solenoid at voltage regulatorr


 I hope you can help me out. I have a 1986 John Deere 330 that was running fine and one day as I was mowing the battery light came on. I planned on just finishing the little mowing I had left and then putting it away until I could figure out what was wrong but something started to smoke in the engine. I got it to the nearest hose and got it out before it started on fire. The wire from the solenoid that goes to the voltage regulator had gotten so hot that it melted the plastic wiring connector as well as some of the plastic in the back of the voltage regulator.
 I have replaced the voltage regulator, the wiring connector, put all new clips on the wires and got it back together. Of course the battery light is still coming on but I don't know why it was coming on in the first place.
 I've had my mechanic over, after much pleading and an attempted bribe (he wouldn't take it),to look at it. The battery checks out to be good, he checked the fuses, the alternator and various other components and isn't finding the problem. He questioned whether I had rewired it correctly, so he rewired it again.
 If he switched the last two wires (one goes to the battery light on the dash the other goes to a relay switch) the battery would over charge or if he put them where they should the battery wouldn't charge.
 Do you think you can offer any help with this issue? My mechanic doesn't want to just start throwing parts at it, and I can appreciate that. I can't send it out to a dealer for repair  without getting it back with a $1000 bill. I am limited in test equipment to a continuity tester but I am willing to borrow or buy what I need to do testing if you need further information.
 Any help you can offer would be greatly appreciated.
 Thank you very much.
         Sincerely,   Yvonne

ANSWER: I need to know what engine is on the mower and I need the engine model, type and code/serial number to look up what charging system you have.

Do you have the Yanmar 3TN66UJ, diesel, 3-cylinder engine?

Have you downloaded the service manual and identified the wiring is correct based on the service manual wiring diagram?

Service Manual URL:

Take a look at the wiring diagram for your mower and let me know if the wiring is correct.


---------- FOLLOW-UP ----------

jd 330
jd 330  

jd 330-2
jd 330-2  
 Thank you for responding so quickly.
 I do have the Yanmar 3TN66UJ, diesel, 3 cylinder engine. The serial # is CH3022D006006.
 I did download the service manual yesterday. I printed out the wiring diagram for my mechanic as he requested, but he didn't come back today.
 I did look it over but I can't tell by the diagram if it is wired correctly. On the diagram the voltage regulator is shown as a square with 3 wire on side of it and 2 wires on the other. On the tractor it is 5 wires in a row. Looking at it from left to right it is wired-red wire to solenoid, yellow wire-yellow wire (pig tailed to plug that goes to the alternator), purple wire that goes to relay switch and brown wire that goes to battery light in the dash.
I know that the first 3 wires are correct. When I wired them the first time I know that they were in the order in which they were originally, I had them marked. When Pat pulled them apart the markers disappeared. My bad, better markers and take a picture next time.
 When he left yesterday he had the brown wire in the fourth place and the purple wire in the fifth place. When I started it today the battery started to bubble within one minute of it running. I switched the brown and the purple wire and started it again. The battery did not bubble, the battery light did not come on either time.
 I don't know if the battery was charging the second time I started it. Yesterday Pat said that the battery was over charging when it was bubbling, and that it wasn't charging when the wires were switched.
 I'm sorry that I couldn't tell if the wiring is correct by the diagram.
 I'll try to attach a couple of pictures. I don't know if they will help or not.
 Thank you again for helping.
         Sincerely, Yvonne

The brown wire does go to the it sounds like it is connected in the correct location, the 4th pin from the left.

I don't see a purple wire on the wiring diagram.  The wiring diagram show a green wire but at the beginning of the chapter that state some things may be different.

If you have a voltmeter you can check to see if the battery is charging.  Connect the meter before starting and note reading.  Start the mower and see if the reading increases.


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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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