Tony in SD
Well-known Member
What resistance measurement should I get for a good magneto/coil on a Briggs & Stratton lawn mower? High side to ground? Low side to ground?
Thanks.
Thanks.
- Thread starter Tony in SD
- Start date
Here is the way I was taught to check a coil on a B&S engine. With an OHM meter, measure from the wire that connects to the points to the wire with the ring terminal that grounds under the coil mounting screw. You should read O[zero] OHMS. Then measure the plug wire to the same ring wire and you should get 4 to 8 OHMS. If both readings are good, the coil is good. If you read infinity in either place, the coil is bad. Good Luck and I hope this helps.
Yes, if you find a totally shorted or "wide open" reading, the coil is "bad".
But, on the other hand, a coil with a shorted "turn" or two will test within the manufacturer's suggested range, yet produce no spark, or a very weak spark.
For a meaningful test, you need a "coil tester" that "rings" the coil, along with the matching tester setup info for you coil, or to sub it with a new or "known good" coil.
Anything less is MEANINGLESS, and a waste of time.
But, on the other hand, a coil with a shorted "turn" or two will test within the manufacturer's suggested range, yet produce no spark, or a very weak spark.
For a meaningful test, you need a "coil tester" that "rings" the coil, along with the matching tester setup info for you coil, or to sub it with a new or "known good" coil.
Anything less is MEANINGLESS, and a waste of time.
Russ from MN
Well-known Member
- Location
- Bemidji MN
You might get more responses if you posted on the garden tractor page.
The coil testers are not always accurate depending on the type of coil. The best test is to disconnect the stop wire, use a spark tester (a Mac one that looks like a spark plug with the center electrode about a 1/4" from the side shell is the best one) and then pull the starter rope looking for a spark. No tester, then use a Phillips screwdriver, put it in the spark plug boot, hold the screwdriver 1/8 to 1/4" from a good engine ground and have someone pull the starter rope if you can't. It works the best to remove the spark plug before doing this test. If you see a spark jump to the ground, the coil is good. If not, get a new one. I have been doing this for 53 years and even though we had a coil tester, this test is the best.
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