Zero RPM reading on R mag

[ernstrm]

I am seeing correct RPM readings when both mags are on and when only the left mag is on, but zero RPM when only the right mag is on. I disconnected the 37-pin connector from the EMS-220 and leads 32 (left RPM) and 33 (right RPM) from the ignition switches and verified that I see 30k-Ohm between the 37-pin connector and each lead. Here is a bit of my schematic, showing the toggle switches--I don't use a standard key switch; the bottom circuit in each switch is so the starter engages only if the left mag is on and the right mag is off:

I know both mag switches work, as I get an audible RPM drop on each single mag and the engine stops when both mags are off.

The data dump shows good RPM readings when on both mags and when on the left mag, but 0 RPM on the right mag.

 

[jakej]

All looks good, for a ‘test’ why don’t you swap the tach leads at the EMS Module & see if the problem ‘follows’ the lead. There could be an issue at the EMS end or the unit itself ?

 

[ernstrm]

I'll try that, thanks!