RPM/MAG Problem

[mmarien]

The RPM drops to zero when I switch the left MAG off. (Lycoming O-320).

I used toggle switches, bought the 30kohm resistors at an electronics shop and connected the P-leads to pins 32 (white/green) and 33 (white/blue). The resistors are connected to the same side of the toggle switch as the P-lead so the EMS pins are connected directly to the P-lead. RPM reads correctly with the right MAG on or off. Engine RPM drops with either mag off and dies with both mags OFF.

Any hints for what to look for.

 

[dynonsupport]

It sounds like the right mag isn't physically connected at all. Otherwise, when the left mag's pulses goes away when you switch them off, the right's would be seen. The RPM inputs are really robust, so it's not likely to be the unit. But to eliminate the unit as a source, you could try swapping around some wires.

Anohter thought - make sure that the right mag's pin is fully seated in the D37 connector and is making electrical contact with the EMS.

 

[mmarien]

Thanks - I'll check the wire for connectivity from the MAG to the 37 pin D37 connector. I have to remove the display to install the filters when they are ready anyhow.

 

[mmarien]

I solved this although not sure how.

I checked the wiring and D37 pins were connected to the same side of the toggle switches as the P-Leads so they was connected directly to the MAG. I inadvertently pulled a wire out of one connector while messing with the wiring so had to redo the connection. Probably a poor connection the first time even though I could kill the engine by grounding the MAGs. The RPM seems to work fine with either MAG now.