Briggs & Stratton Battery Not Charging – Simple Voltage Regulator Test



PLEASE USE THIS VIDEO FOR INFORMATION PURPOSES AND TAKE ALL PRECAUTIONS WORKING ON POWER EQUIPMENT, FAILURE TO DO SO COULD KILL OR SERIOUSLY INJURE YOU. The battery on my lawn tractor started going dead and I’d notice the needle was staying on the negative charge side of the amp meter so I dug into the charging system and here is what I found. The charging system is pretty simple, the engine has an alternator under the flywheel that puts AC volts into the Voltage Regulator, the regulator changes it to DC volts and regulates the output, the output goes to the battery via a wire that may go through a relay and fuse. If you have plenty of AC volts coming out of the alternator and battery volts (less than 12.5 volts) on the wire going to the battery (at the connection to the regulator), the voltage regulator is the only thing left and is probably bad. What you see in this video should apply to any engine with a 3 wire voltage regulator. Unfortunately the regulator itself can’t be checked with a normal volt/ohm meter so this diagnosis is through process of elimination.

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23 thoughts on “Briggs & Stratton Battery Not Charging – Simple Voltage Regulator Test

  1. loved how you explained every step. and gave a few methods of testing. couldn't make it any easier unless you come and tested it for me.

  2. Thanks for posting. Quick question. From alternator i have 50 volts out. When engine not running and i connect alternator cable to regulator cable it smokes. I have 12 volts in regulator cable. So if running i will have 12v and 50v ac hitting each other. Should there be 12v dc where alternator cables are going in?

  3. Curious, would this rectifier regulator power a load such as lights only without a battery? What is the topology of the regulator? Linear? Switchmode step down buck?

  4. Ok, so the "bad" regulator was still producing over 12 volts & the "good" one was over 15. If the battery is 12V why would the voltage regulator be bad then??

  5. Excellent video! Very specific, detailed and easy to follow. Thank you! Your video was extremely helpful and allowed me to troubleshoot my JD LT145 and get straight to the problem (imagine that, it was the voltage regulator!). You definitely saved me $$$. Just wanted to say thanks for taking the time to help us 'do it yourselfers'. 👍👍👍

  6. Great video! This made it simple & helped me diagnose my hustler super z. I couldn't figure out if it was the regular or the alternator. I was confused about how to test the system, But after your video I checked it. And it's the regular. Thanks!

  7. This was absolutely one of the best do-it-yourself helpful videos on you tube. I thought it was my alternator, glad I  stumbled across this video. Did all your suggested test with my volt meter, and found out it was my voltage regulator. My mower battery and I thank you… Outstanding Video snaproll94e!

  8. Sounds like you need a valve adjustment. When that engine doesn't kick over right away then the compression is not releasing causing it to hesitate. Great video man ~!~!

  9. Good and very informative video. Sounds like your valves need adjusting because of the way it turns over when starting. Thanks for the video.

  10. This is the best expained video I have watched on youtube. Told me exactly what I need to know. I will check my dads mower tomorow. Thanks for the well explained info and your time.

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