Vans Tachometer irregular RPM's

Hello everyone;

Last week I had a " Brain fart" I was doing a run up prior to my flight, and I noticed that my engine was running rough. I suspected that, with so many touch and go's that it was carbon'd up. But then I noticed that my RPM's on my tach did not match with what the engine was running.
I cleaned my plugs and started the engine and my tach was still not working properly. The brain fart was that I ran the engine with only one mag for about 15 minutes. Could this cause issues with the tach?

Bob Wieczorek

Are you using the mechanical tach transducer? It has a limited life of about 6-8 hundred hours . I'm probably about due to expect a need for my second one.

Mechanical tach

My Tach is a mechanical transducer. I feel possibly that the irregular performance
may be electrical?
Bob

tachometer

The engine has 26 hrs.
Bob Wieczorek

I've replaced the mechanical tach transducer... It first failed intermittently - RPM would be good, then would bob to zero for a moment and return to normal. Then one day at start-up, NADA. Replaced the sender and everything returned to normal. Then I noticed the sender was backing out of its threads slightly so I purchased a short tach cable which allowed me to mount the tach sender in an Adel clamp on the firewall and connect to the shaky-shaky engine via the short flexible tach drive cable. That was a half dozen years ago and it's working like a charm.