Briggs & Stratton Engine – Alternator and Voltage Regulator Replacement

This video covers the steps I took to replace the ALTERNATOR on my 18.5HP Briggs & Stratton Engine for my Craftsman Riding Mower. This included replacing the VOLTAGE REGULATOR and removing the FLY WHEEL. I include a lot of detail footage showing each step involved in getting to…and removing…the Fly Wheel in order to access the Alternator. I show how to use a MultiMeter and the Mower’s AMP METER to isolate the problem…and verify I fixed the issue. I replaced the ALTERNATOR (and VOLTAGE REGULATOR) because my Battery was not charging…the mower’s Amp Meter was in the Negative Area (indicating it was DISCHARGING my Battery) instead of in the Positive Area (indicating it would be Charging my Battery).



22 thoughts on “Briggs & Stratton Engine – Alternator and Voltage Regulator Replacement

  1. You can get parts for your engine from B&S or from the mower manufacturer. Any mower parts store can look up the current part number for your mower.

  2. SAE threads does not mean English threads. Most European threads including England's are in MM / millimeters which different from American. SAE means Society of Automotive Engineers which are our most commonly used American machine /auto threads of which you have two of these daily used types, [standard UN, Unified National sometimes UNC /coarse ] , exam: 1/4 -20 threads per inch [ UNF ,Unified National Fine] exam: 1/4 -24 threads per inch. You can get into another whole world of these things such as NPT , National Pipe Threads, which most commonly used around the house (water, gas,, etc.) are tapered.

  3. To find the correct parts for your mower engine, use your engine model number (e.g. 31P777-0348-E1 as in video) and look them up online at or You click on parts diagrams and then use your model number. They will show the parts breakdown for that model. The paper manuals may show other engine models available for that mower.

  4. Alright boys I got a question for you now I'm no mechanic I can make the turf in your yard look like the Masters had Augusta National but again I'm no mechanic I recently had a Kohler Engine on my Walker that wouldn't work with a brand new battery took it in and it was the voltage regulator and a fuse they had it for about 3 days the total charge was a hundred and thirty bucks with labor am I getting ripped off or is this at the high end of reasonable I do not know if they put a new battery in yet…. would that cost be reasonable with a new battery? let me know boys

  5. How do I find my replacement part for my alternator? The number I provide no one seems to have it. The model numbers have to match or am I wrong? My model is 31C707-0230-E1

  6. It would have been helpful to see you testing with multimeter to determine faulty parts and again testing after completion (which leads and setting on multimeter to which wires on voltage regulator and alternator. Otherwise, it was a good video.

  7. B & S does have a manual showing all the alternator and regulator permutations with wiring diagrams for each – any of them can physically fit the engines, even the dual half wave dc and ac alternators that are split electrically – and there is a higher amperage unit to attach to the rectifier as well. Also some regulate current instead of voltage…

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