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What should the voltage be while running?

Discussion in 'Mechanic and Repair' started by CRUZMISL, Aug 23, 2005.


    CRUZMISL LawnSite Member
    from zone 6
    Messages: 186

    I have a JD SST16 that is having some issues and I'm not sure if it's the battery or the charging system although I think it's the latter.

    Today the tractor wouldn't start so I put it on the trickle charger and waited a few hours. I came back and it sparked right up. I cut a lawn and tuened the tractor off and it wouldn't start, voltage was 9V. Trickle charged it again and the voltage was 12.24V and while running was about 11.8V, I turned the lights on and it dropped to 11.6V. I'm thinking the charging system took a dirt nap. Are the charging systems complex? Any ideas?

  2. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    A bad battery will give you a low charging system reading, The fact that it had 12.24 doesn't mean it's good because at that time it had what is called a surface charge in it. I would suggest taking the battery out and take it to a auto parts store or some other shop where they have a load tester to properly test it. If it test good then worry about the charging system, and should it be (that) post the model and spec. numbers off the engine so we can see what it is.
  3. Brianslawn

    Brianslawn LawnSite Silver Member
    Messages: 2,004

    running it should read at around 13.8-14. anything under 12 is not charging. yes, could be bad battery. might also be dirty cable connector or bad battery to frame ground. you should be able to check output voltage of regulator/rectifier. even if it is bad battery you might want to go ahead and check the rest, to prevent more probs down the road.

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