I've had occasional issues with the non-operation of NAV and COM radio switches. Twice I have been unable to tune either the COM or NAV switches, although the transponder worked ok. Both times the COM issue wasn't critical because I fly with Radar Contact and the radios are usually tuned via that program instead of manually, but my ILS approaches were impossible because the NAV radios could not be tuned to the localizer freq. It was sort of interesting the first time it happened because I treated it as a failure and diverted to a field with VFR conditions, but the second time was just annoying. I haven't figured out what caused that, but is it normal that the transponder switch is always tunable while the COM and NAV switches only work after power is available to the radio panel?Any ideas what may have caused the switches not to work? Obviously (maybe), buss power was available to the radios when the malfunctions occurred because everything else seemed okay and there were no annunciator flags. Keith

The symptoms are that the Avionics Switch is off. You can't control it inside PMDG but you can assign a key or button for it in FS9.If you load through a default FS9 aircraft (cold and dark) make sure the Avionics Switch is left on before you change aircraft.David.

You can assign a keystroke combination to the avionics master and turn it on within the cockpit of the 737. I use Control+K so I can remember it. Bob K

Try turning the battery toggle switch off and then back on....that is the covered switch on the overhead.....this has always cleared the problem for me.Paul

Hey, you guys, thanks for the feedback!I'll try your suggestions. I think I might have toggled the battery switch in my attempts to make the radios work, but who knows. I believe I read that the 800/900 upgrade features a more realistic radio panel, among the many other improvements, so perhaps an avionics master switch will be included. The more switches, knobs and buttons, the better!Keith

The Admin should make this a sticky. Solved my radio problem.Thanks,Terry 'netguru' McPeck

Hi,I'm also having problems with radio not tuning after an hour of flight. I'm tried toggling the battery with no avail, I've also assigned a keystroke to avionics but still no good.I'm using the registered version of FSUIPC. I guess my flight with these wonderful aircraft are over until PMDG fixes or responds to this.Thanks,Sean

I had the problem after a clean install of FS9 (just for the PMDG 738 ;)) and realised it was due to FSUIPC "extend battery life" toggle wasn't on. Now you can only do this in a full FSUIPC and not in the free one so....PMDG is this an issue you guys missed? Other than that - WELL DONE!Ian Bowden