MGL Avionics User Forum

Good day gentlemen/ladies,

I have an early Odyssey ( s/n 0620) that was purchased in 2007 and now I'm finally getting ready for first flight ( I know I purchased it way too early and it took over 15 years to complete my RV-7A..). I am not getting any RPM indication on the display though all other inputs & reading seem to work fine.

Details:
- Odyssey EFIS with Gen 2 upgrade done
- UMA T1A9-1 tach sensor installed on Slick mag
- RDAC X-D

- Wiring and installation per the included instructions and pictures for the UMA sensor.
1. A 22k pullup resistor included and used with a connection from 12 VDC + ( RDAC power) to the signal line (white lead from UMA) input.
2. 12 VDC power to orange/white lead to UMA sensor.
3. Blue/white lead and shield from sensor attached to negative supply from RDAC which is ground as well.
4. BALLAST jumper removed from RDAC.

- EFIS menus set for RPM with 1 RDAC in system, 2800 RPM alarm and 2700 RPM warning. Lowest RPM displayed set to 300 RPM.
-Engine started, ran fine but 0 RPM displayed. Other engine readings ok ( fuel tank level, CHT & EGT, fuel pressure, oil pressure & temp, manifold pressure).

- Checked output from UMA sensor and output on white signal wire was 12 VDC for 1/2 prop turn and 0 VDC for the other half turn.
- Ground connection at RDAC was less than 0.1 ohm resistance to engine block. Still, I added a separate ground lead directly from RDAC ground to engine block and still no readings.
- Removed DC jumper from RDAC no change.
- Reinstalled BALLAST jumper ( both jumpers now installed) no change.
- Checked voltage at RDAC Rev counter input with all wiring in place[/b] and 12 VDC+ showing for 1/2 prop cycle and 0 VDV for the other half cycle.

I'm stumped ! Is there any input I can put into the RDAC Rev counter to confirm the RDAC is good ?

I'd be surprised if the RDAC had a bad channel as it has never been used until recently. If it's bad I don't think I can order a new one as it's obsolete and not available anymore.

Any ideas or suggestions much appreciated.

Russ

Hi Russ,

I have just read your post, here is something that comes to mind.

I can see you have made other settings in the RPM setup Menu, but have you also set the number of pulses in the RPM setup menu.

Cheers
JimJab

P.S. Congratulations on your build.

I also had a major problem trying to get the RPM to display, but mine was from a Lightspeed electronic Ignition.
Finally , in desperation, I bought a cheap digital tacho on ebay and connected up in parallel with the EFIS tach.
To no ones surprise, the new tach worked perfectly.
To my complete surprise, the tach now displayed on the Odyssey.
It turned out to be a faulty earth.
The only way I found this was to take each wire from the new tach one at a time till I found the culprit.
Mick

Were you able to solve your issue? I am facing the same exact problem with my odyssey and wondering of somone was able to figure it out