Avionics master switch needed

[mooneyflyfast]

I’m needing an avionics master for my 81 J model.  It’s a Klixon20tc2-Bg-3. Any help locating one would be appreciated.

[47U]

On 5/23/2022 at 1:46 PM, mooneyflyfast said:

20tc2-Bg-3

Several prospects on a controller.com part number search…

https://www.controller.com/parts/search?SearchType=Start&PartNumber=20tc2-Bg-3

[tony]

Is the avionics master something that is part of the type data or do you think it was a mod after it left the factory?

[mooneyflyfast]

It’s original made by Klixon which says it’s obsolete.  Aircraft Spruce has a reasonably priced combination Toggle switch/5 amp (not 3) breaker which it says was original equipment on many Cessna, Beech and other AC. Another option might be a plain toggle switch with a 3 amp inline fuse.  I need to talk to my radio shop about the feasibility of one of these. These Klixon rocker switches are a pain and I would like to eliminate them if possible.

[mooneyflyfast]

Thanks 47U. I’ll look into these.

 

[mooneyflyfast]

I ordered a new one from Select Airparts 

 

[carusoam]

Inviting @bmcconnaha

Discussing avionics master….

-a-

[Dave Morris]

Or get rid of that thing that's a single-point-of-failure for your entire stack called the "avionics master switch". Here's what an avionics guru says about it:

http://www.aeroelectric.com/articles/avmaster.pdf

 

[carusoam]

6 minutes ago, Dave Morris said:

Or get rid of that thing that's a single-point-of-failure for your entire stack called the "avionics master switch". Here's what an avionics guru says about it:

http://www.aeroelectric.com/articles/avmaster.pdf

 

Dave,

Adding to the confusion….

Mooney Avionics Master Switches are selected and wired to not be a single point of failure… (pretty fancy detail, often discussed around here)

When they go to Europe… a second switch is added so the avionics bus, and has even better protection from failure….

 

What was the avionics guru suggesting as an alternative… let the avionics fend for themselves?  I was speed reading the multi-paged article… 

Best regards,

-a-

[Dave Morris]

4 minutes ago, carusoam said:

Dave,

Adding to the confusion….

Mooney Avionics Master Switches are selected and wired to not be a single point of failure… (pretty fancy detail, often discussed around here)

When they go to Europe… a second switch is added so the avionics bus, and has even better protection from failure….

 

What was the avionics guru suggesting as an alternative… let the avionics fend for themselves?  I was speed reading the multi-paged article… 

Best regards,

-a-

Bob Nuckolls debunks the old wives' tale about voltage spikes and about modern avionics not being able to handle an engine being cranked, but suggests anyone who is fearful just turn off the radios individually. The complexities of adding more switches and relays and stuff to invert the master switch are just more points of failure. The later Mooneys with an essential bus are the right way to go, but what's a 1968 airplane owner to do except try to eliminate single points of failure, because we all know that switches eventually fail. He has massive amounts of information on that web site for people building experimentals who want to have the most robust and modern electrical systems.

[PT20J]

Many of Garmin's STCs require connecting some units to a switched avionics bus rather than the battery bus.

According to Garmin, the concern is brownout during start on 14V systems. Some Garmin equipment (such as PFDs for instance) require connecting to the battery bus but have low input voltage protection in the power supply. 

Skip

[tony]

On 6/5/2022 at 4:01 PM, Dave Morris said:

Bob Nuckolls debunks the old wives' tale about voltage spikes and about modern avionics not being able to handle an engine being cranked, but suggests anyone who is fearful just turn off the radios individually. The complexities of adding more switches and relays and stuff to invert the master switch are just more points of failure. The later Mooneys with an essential bus are the right way to go, but what's a 1968 airplane owner to do except try to eliminate single points of failure, because we all know that switches eventually fail. He has massive amounts of information on that web site for people building experimentals who want to have the most robust and modern electrical systems.

Just add a redundant switch.  Is Bob going to pay the repair bill when my Nav Com stops working?