Chasing RDAC gremlins

[DEW]

Chasing three gremlins ( and maybe setting gremlins as well) without much success
Running the Challenger lt system with extender to get the AOA, a Lyc O 360 with duel P mags.

1: The display shows 4 EGTs but only 2 CHTs. I've checked that the Demo mode is not selected and that the lines are landed correctly on the RDAC. Also checked to make sure only the first 8 channels are set up to scan 1. The last 4 channels are not set to scan. MGL senders.

2: The display does not show a fuel pressure indicator. A UMA sender from MGL is installed. 12 volts supplied, grounded per the instructions with the sender. Settings are automotive resistive, 200 ohms, 1 to 35 PSI. The dip switch on the RDAC is On for the fuel pressure. The display does show a FF indicator but no FF is installed.

3: MGL resistive fuel quality senders. Tank 1 is fine. Tank 2 reads 7/8 full (264 raw level reading) with the tank empty. After checking all the wiring and terminals, changed that sender to a new sender thinking the sender was shot. The new sender gets the same reading. Checked to make sure no virtual tank settings were selected.

I've taken a photo of the RDAC 1 diagnostics screen and can add the photo tomorrow.

Any advice?

Thanks DEW

[adamoconnor]

Chasing three gremlins ( and maybe setting gremlins as well) without much success
Running the Challenger lt system with extender to get the AOA, a Lyc O 360 with duel P mags.

1: The display shows 4 EGTs but only 2 CHTs. I've checked that the Demo mode is not selected and that the lines are landed correctly on the RDAC. Also checked to make sure only the first 8 channels are set up to scan 1. The last 4 channels are not set to scan. MGL senders.

Have you set the proper engine monitoring mode on the EFIS' "Standard System Selections" menu? Sounds like you're in Rotax mode...

2: The display does not show a fuel pressure indicator. A UMA sender from MGL is installed. 12 volts supplied, grounded per the instructions with the sender. Settings are automotive resistive, 200 ohms, 1 to 35 PSI. The dip switch on the RDAC is On for the fuel pressure. The display does show a FF indicator but no FF is installed.

If you are using a UMA sender, your settings on the RDAC and the EFIS are incorrect. UMA senders are active, voltage senders. So, Pull Up Switch on RDAC stays OFF, and the setup on the efis needs to be set to the effect shown here: https://support.michiganavionics.com/po ... and-wiring

You also will want to turn FP on in the Standard System Selections menu

3: MGL resistive fuel quality senders. Tank 1 is fine. Tank 2 reads 7/8 full (264 raw level reading) with the tank empty. After checking all the wiring and terminals, changed that sender to a new sender thinking the sender was shot. The new sender gets the same reading. Checked to make sure no virtual tank settings were selected.

Have you tried re-doing the calibration? A reading of 264 means the voltage is almost all the way to ground, which on float-style senders can mean either full or empty, depending on the orientation of the sender in the tank. What does your fuel calibration table for this input look like?

[drvale]

I would suggest methodically disconnecting each sender - that means all of them in turn. I had erroneous readings like high Oil pressure when the fuel tanks were full. Eventually tracked down to a faulty rear fuel sender giving me high Oil Pressure. Rainier thought it was an earth problem to the engine block which it wasn't but could well have been the faulty sender grounding to the tank and therefore causing an earth loop.

[DEW]

Thanks for the help Adam and Dave.
Items 1 and 2 were settings as you suggested.
I'll work on the fuel sender this weekend.

DEW