Just Fried a New Coil with my Mercotronic

[kevinrude]

Was performing the Coil Power Test (#1).
It fried the primary winding, which I verified using the "Doug Penn" method shown here:
https://www.youtube.com/watch?v=KT8rk5QWgS0
Secondary winding is still OK (not that it matters).
What did I do wrong?
Anyway, hoping to get an answer so that I don’t do this again and hopefully others can learn from my mistake.
Thanks.

[dave-bernard]

did you follow the instructions?????
If you don’t have them Ebay has them I just looked and found them.

[kevinrude]

quote betty ann bernardd:

did you follow the instructions?????
If you don’t have them Ebay has them I just looked and found them.

Yep.

[frankr]

Are you sure? It would seem very unlikely. Is it "open" (no continuity)?

[kevinrude]

quote FrankR:

Are you sure? It would seem very unlikely. Is it “open” (no continuity)?

Yep. Using a regular multi-meter, i put one lead on the ground wire and one lead on the wire that goes to the points, the needle doesn’t move. When I test a good coil this way, the needle swings hard to the right side of the meter, indicating continuity.

[frankr]

Is the Merc tronic still working on other coils? Just guessing, I suppose it might be possible that it supplied a constant voltage to the coil and overheated it. But one would think you would have seen it smoking before that.

[bill-mcnamara]

Very timely caution there Kevinrude.
I’m going to pick up my "new to me " and first Merc-o-tronic tomorrow morning, guess I should read the book before trying it out huh?
Some of us seem to have trouble asking for directions, or reading instructions.

Purchasing from the original owner, who has the literature for it. Will also ask for a demonstration, since I’m picking up some coils too.He has also included some sort of resistor so that it can be powered by a 12V battery.

[jerry-ahrens]

Gosh, I think it would be hard to burn out a primary winding with a coil tester…. maybe the machine put to many amps into it? if I remember right, the Mercotronic works about the same as my Stevens machine, with a variable output to the coil primary. It may just be a coincidence, that you simply have a bad coil there.

[oltimer]

quote FrankR:

Is the Merc tronic still working on other coils? Just guessing, I suppose it might be possible that it supplied a constant voltage to the coil and overheated it. But one would think you would have seen it smoking before that.

I have been using my model 98 Merc-O-Tronic for 30 years, and am leaning to what Frank has quoted. The 7 volt battery for coils, and wall plug in electricity for the condensers is "my unit". I am also wondering about the ground connections in your unit Kevin? Check them very close.

[eviltwin]

New part? It must have been damaged in shipping or was defective. Ask for a refund. Unless they can prove otherwise you are covered.

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