MFD range switch failure

[Eric N]

On my most recent flight the MFD range knob began to act up, sometimes doing nothing when it was twisted, and had something of a gritty feel as well; the "joystick" function seemed fine. I called the avionics shop on our home field and was told the unit could be repaired, would need to go back to Garmin, would cost ~$1500 flat-rate. Intermittent failures like this are frustrating, but I'm not inclined to take a chance with this particularly important function. Anyone had a similar experience. The aircraft is a 2005, bought new from the factory, with 1200 Hobbs hours.

[CFIDave]

A cheaper solution some people have tried is to swap PFD and MFD units, since the range knob is rarely used on the PFD. You'd still have to pay for a tech to swap hardware and change the G1000 software configuration. This also won't work for newer DA40s equipped with the GFC700 autopilot, since the autopilot buttons are only located on the MFD bezel surround -- but it would work fine on a 2005 DA40 where PFD and MFD are identical.

[Colin]

I lost two (the joystick function was lost) early on in my ownership, but they have been solid since. It definitely seems like a $60 part they should be able to swap in, but they had to replace the entire unit both times.

[rwtucker]

There is a good change that this knob connects to a digital switch, meaning that it is opto-electric and there are no physical contacts to clean. If it is opto-electric, you could try cleaning the inside of the switch body with compressed air, if you are electronically handy and can get at the switch (basically an air gap between an LED and a photocell, or similar; the detents are mechanical ribs designed to provide haptic feedback and have nothing to do with the actual electronics. If it is mechanical, contact cleaner might do the job. I haven't been inside of the MFD but my guess is that the neighborhood is crowded!

Do you get a lot of dust where you fly? If so, and if that is the cause, it might be worth sealing off the rear panel compartment a little better than factory.

[Eric N]

Robert, we're right on the coast in SE CT, so I wouldn't expect dust is the issue. The switch doesn't seem very accessible and I'm not comfortable with spraying anything into it or attempting to take it apart. I expect we'll go for the flat-rate repair, though on the most recent flight it worked fine, though it still seemed "gritty" compared with the other side.