I have a S-Tec 30 AP with GPSS which is nicely driven by my 420W.

I'm have already installed the switch to allow the 3400 and Garmin 420W to drive the AFS Pilot when it is installed.
The output from the switch serves as input to the GPSS converter on my S-Tec 30 and that part seems to work well with the switch in the 420 position.

I have Port 1 set up as AVTN/ARNAV
Port 2 is disabled
Port 3 is SL30
Port 4 is ARINC
GPS/NAV1 data source is serial4
GPS/NAV2 data source is serial3

When I run the diagnostics for the ARINC module - it detects my GPS but not the VOR - expected as I have a 420W which doesn't have the VOR built in.

I am still ground testing and have not finished installing the magnetometer.

When I switch over to the 3400 source for the autopilot input - it acts as though there is no input at all.

Is it possible that the missing magnetometer prevents the 3400 from sending signals to the S-TEC 30's GPSS coupler? It would make sense as a safety feature. The 420 works fine so I know the logic is set up correctly.

Any help is appreciated....even tell me to finish the magnetometer and try again....which is my current plan.

Ralph Capen