Master Switch Breaker

[Txbyker]

Has anyone had the master switch start powering on all avionics without switching on the avionics master?  On my last flight my master switch, switches on all internal electronics.  I had some avionics work done a few weeks ago and the avionics shop commented about how close the master and radio master breakers are.  I believe they may be touching. 

 

Russ

[Marauder]

Russ -- it can be a few things. My F did not have an avionics master when I bought it. I needed to shut off everything in the stack before turning on the master and starting up. In my case I have a standard rocker switch that switches a relay. It will not power the stack unless the master is on and then it is turned on. If you are setup this way, I would suspect a bad avionics switch. I would have hoped your avionics shop could have diagnosed something that simple. On the newer Mooneys, I am not sure how their avionics switch works. Sent from my iPad using Tapatalk

[Txbyker]

Had an A&P look and he believes the relays behind the fuse panel are too close and one is controlling the other.  Make sense?  Whats the easiest way for us to get to the relays, remove the fuse panel or from above with no glareshield?

[David Mazer]

I have had an ongoing battle with my avionics master since I've had the plane.  Sometimes it works, mostly it doesn't.  I've had three shops look at it without resolution.  I may need to replace the relay but that is apparently a big and expensive job.  Better luck to you than I've had.

[Alan Fox]

The avionics master is set up to fail closed , in other words if any part of the avionics master circuit fails it turns on the avionics bus.....The problem is usually one of the two relays behind the circuit breakers .....

[flyboy0681]

I had the identical problem last year. It turned out to be carbon buildup on the relay contacts. My avionics shop removed the relay and cleaned it, a potential savings of thousands over a replacement.

[Txbyker]

Thanks! In this case it was a loose nut on the master switch power cable terminal where it connected near the relay.