Front tach inop

Burt · #1 12-06-23, 08:18 PM

I have a 1966 337A and the front tach has gone inop. Tried switching front and rear leads on the back of the tach and there is nothing wrong with the instrument. My Service Manual shows a tach pick-up coil on the bottom of the right magneto. But the only thing on the bottom of my right magneto (both magnetos actually) is a Magneto Filter Capacitor and the one on the right mag seems to be connected to the tach. I have continuity in the lead from the tach to the filter capacitor. Not sure where to go from here. Anyone have experience with this setup?

Burt

Frank Benvin · #2 12-06-23, 11:17 PM

There should be a sensor on the mag This is off my 1967 337b

You can see it on the right side - the red sensor

TomM · #3 12-07-23, 11:24 AM

Mine actually went out as well. Had been acting up (bouncing around and pegging off the scale). Had the mags rebuilt for the engine overhaul and he checked the pickup and said it was fine. Reinstalled and did the same thing. Mechanic checked the wires to the tach and they were good.....frustrated I just replaced it with an Aerospace Logic electronic tach at annual (now). They make a "front/rear" labeled version. Trouble shooting can suck up a lot of time and when I cant do it myself, I draw the line when the finances just dont make sense.

When I get my plane back (next week) I would be more than happy to send you one of my pickups if you think that would be of help to troubleshoot this issue.

Burt · #4 12-08-23, 03:05 PM

Thanks to Tom, Frank, and Randy for your kind assistance. I was able to troubleshoot the system and discover that my sensor as well as my tach are functioning properly. The problem is with the prop sync transmitter or the wiring associated with it. I bypassed it by connecting my sensor directly to the tach and the tach is now functioning properly. Next I will troubleshoot the wiring associated with the prop sync transmitter and if that all checks out I will start looking for a replacement transmitter.
Burt