John Deere 318 Charging Problem

Discussion in 'Mechanic and Repair' started by Weedburner, May 26, 2007.

  1. Weedburner

    Weedburner LawnSite Member
    Posts: 99

    Working on a John Deere 318 with a Onan engine. Does not charge properly. Battery light comes on if you start the mower deck or turn on any lights. Tried a new voltage regulator, didn't help. I checked to coil with a continuity tester and it check almost no resistance, so it's not open. Battery tests about 13 volts with the engine running and about 12.5 with it shut off. Any ideas?
     
  2. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    Check across the outer two terminals on the rectifier/regulator. Set your meter on A/C volts. There should be at least 28 A/C volts at full throttle. If not then change out the stator. If there is 28 volts then check the center terminal. There should be battery voltage there. If there is then it's the regulator. If not trace the wire and repair. Also have you lights on at full throttle when checking across the battery. You need more than 12.6 volts to get a charge in a battery. This will at least get you started. Post back with your readings for more help if needed.
     
  3. Weedburner

    Weedburner LawnSite Member
    Posts: 99

    The stator checked almost 40 volts across the wires with the engine at full throttle. The center lead had battery voltage. Replaced the regulator with a new one, the battery light is still on. Will trace the wiring and look for other problems.
     
  4. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    What is the battery voltage at full throttle and the lights on? Sorry I made you change out the regulator again. Make sure all grounds are clean and tight. It's sometimes hard to repair mowers with words.
     
  5. Weedburner

    Weedburner LawnSite Member
    Posts: 99

    Battery shows 14 volts. I found I could make the battery light go off and on by wiggling the wires going to the ignition switch. Will pick up a new switch in the next couple of days and try that. Problem may be the switch or the harness. The wires that connect to the terminal on the edge of the switch rather than the main harness appear to be the problem. They are hot with the switch in the run and start position.
     
  6. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    It's charging alright. Sounds like your on to the light issue. Let us know.....
     
  7. Weedburner

    Weedburner LawnSite Member
    Posts: 99

    New ignition switch fixed the problem.
     
  8. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    Great job! The Onan is built as tough as they get!
     
  9. dsscrusher

    dsscrusher LawnSite Member
    Posts: 4

    I have a similar problem. Same 318, using P218G engine. No power, and engine won't run unless connected to charged battery. Changed voltage regulator/rectifier, still same problem. Voltage at AC is 38-42 VAC. No voltage at the bat Term. Checked with both machine ground and to the aluminum plate/heat sink of the regulator. Could it be the new from JD dealer, voltage regulator is bad?
     
  10. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    With the key in the (on) position you must have battery voltage at the center connection on the regulator. If not trace the wire back and find the problem.
     

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