One Rotax 912ULS TWO Tachometers!
in 912 / 914 Technical Questions
6 years ago
Folk,
I previously had a completely functioning EFIS attached to my Rotax Engine - Actually along with all the other engine instrumentation, the Rotax Tach goes to a RDAC box in the engine compartment and then 3 wires feed the RDAC information to my EFIS.
Anyway, I purchased another Tachometer with non-volatile Tach hour memory (no battery), because the EFIS backup battery has previously died and lost all my Tach / Hobbs data!
As per instructions, I simply connect the new Tach RPM input to the same output from the Rotax CDI. The RDAC, new Tach and EFIS all share the same engine ground. Anyway, the new Tach also came with a 200K Ballast resistor which they say can be connected between its tach input and ground, so....
When I connect the EFIS and new Tach to the same Rotax CDI output, the EFIS tach works, but the new Tach is very unstable and reads around 3 times the correct reading.
When I connect the EFIS and new Tach to same Rotax CDI output but add the 200K ballast resistor between ground and the Rotax Tach output, the new Tach is stable and acurate, but now the EFIS tach reads ZERO!
Does anyone have any experience / suggestions?
For what it is worth, Both the EFIS and new Tach are from the same manufacturer, namely MGL avionics, with an Enigma Stratomaster EFIS and VEGA MAP3. All I get from MGL is that 'it should work'!
Roger
I previously had a completely functioning EFIS attached to my Rotax Engine - Actually along with all the other engine instrumentation, the Rotax Tach goes to a RDAC box in the engine compartment and then 3 wires feed the RDAC information to my EFIS.
Anyway, I purchased another Tachometer with non-volatile Tach hour memory (no battery), because the EFIS backup battery has previously died and lost all my Tach / Hobbs data!
As per instructions, I simply connect the new Tach RPM input to the same output from the Rotax CDI. The RDAC, new Tach and EFIS all share the same engine ground. Anyway, the new Tach also came with a 200K Ballast resistor which they say can be connected between its tach input and ground, so....
When I connect the EFIS and new Tach to the same Rotax CDI output, the EFIS tach works, but the new Tach is very unstable and reads around 3 times the correct reading.
When I connect the EFIS and new Tach to same Rotax CDI output but add the 200K ballast resistor between ground and the Rotax Tach output, the new Tach is stable and acurate, but now the EFIS tach reads ZERO!
Does anyone have any experience / suggestions?
For what it is worth, Both the EFIS and new Tach are from the same manufacturer, namely MGL avionics, with an Enigma Stratomaster EFIS and VEGA MAP3. All I get from MGL is that 'it should work'!
Roger
