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Avionics Master Relay


Jack46

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2 hours ago, Jack46 said:

It is becoming more and more likely I will need an avionics master relay for my 1988 "J". Mooney no longer supplies that part. Any suggestions on where to find one?

What is wrong with it?

the one in my 77J was more commercial looking then aviation. It kept breaking the mounting tabs so I drilled a couple of holes in the shelf it mounts to and put a ty-rap around it. It hasn't broken loose sense.

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The failure mode is, it sticks on. Meaning, when I put the avionics master in the "off" position, everything stays on and I have to shut them down individually. That means, after start up, they have to be all turned on individually.

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It wouldn't make sense to me that Mooney no longer supplies this part... and leave you hanging.

It would be best to call Lasar.com, an MSC, for pro help with Mooney related parts...

Of course, Aircraft Spruce is pretty capable of supplying a direct replacement as well...

PP thoughts only, not a mechanic...

Best regards,

-a-

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On 12/3/2017 at 11:57 PM, carusoam said:

It wouldn't make sense to me that Mooney no longer supplies this part... and leave you hanging.

 

Are you kidding me?  Anthony, wait until your aircraft becomes old like mine.  The factory has all but abandoned support for an older model like mine.  Thank God for LASAR.  

Edited by tony
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Tony,

I must have inaccurately portrayed the situation...

The relays are commercially available because they are standard industrial products.

MSCs like Lasar, make it easy to purchase the right technical device for our application.

The factory, when open, has been pretty good about supplying the tech details to support the MSCs.

I remember buying my 1965 M20C when the factory was closed.  I was Willing to take on the risk of parts availability.  Mostly because these small wear parts are not made by Mooney, and can be sourced externally when needed.

Today, the factory is open.  

The MSCs are good at supporting our planes.  Some join us daily and engage in conversation on MS...

Finding a proper relay shouldn't be more challenging than calling Dan at Lasar, and having a mechanic swap out the part.

Of course, there is going to be a price to pay for all that 'convenience'.   :)

As fancy as the Long Bodies are.... Many aren't spring chickens any longer.

As far as the business model of Factory and Service centers goes... This has always been a challenge to understand and navigate. ESpecially when you need a part now, and it is on a shelf somewhere..... nearby at an MSC, or in Kerrville, or in an MSC across the country.

I'm confident that the OP can get a proper part through the factory/MSC model.... even if the original part number has changed several times and the original part number no longer exists...

COuld be just my positive PP thoughts only. I'm not a mechanic...

Best regards,

-a-

 

 

 

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Real important for Jack the OP...

Check the wiring diagram on how the relay is intended to work...

The Avionics relay normally fails closed...

The Master relay being turned on, opens the Avionics relay...

Turning on the Avionics, then re-closes the Avionics relay...

 

You might find that the Avionics relay, may not be getting power from the master relay... this would be keeping the Avionics relay closed.

Check to see if the relay is working, it may be a wire not supplying power to the relay to open it....

 

The purpose of this complexity... if there is the failure of the Avionics relay... it fails closed, supplying power to the Avionics.... :)

PP thoughts only, not a mechanic...

 

Best regards,

-a-

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14 hours ago, Jack46 said:

The failure mode is, it sticks on. Meaning, when I put the avionics master in the "off" position, everything stays on and I have to shut them down individually. That means, after start up, they have to be all turned on individually.

Actually, failure mode for that is on (NC), the relay is not engaging to open the circuit. check that you have power to the relay and that the ground is good. 

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  • 4 years later...

Sorry to rehash an old thread but...

New pilot, 1975 M20f. Recently had a mid air total avionics failure, 375, 430, stormscope, engine monitor all shut off. Upon turning the avionics switch off and on they came back on for about a second and died again. 

Locql avionics shop said it was a relay. But according to the internet and you guys, it should have failed on. Are they misdiagnosing this or is it plausible? 

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If you have an avionics master rocker switch like my 81J model it has a built in 3 amp breaker.  If it fails it will shut off all your radios.  Mine was a Klixon which was discontinued but I was able to find one by using the model number from the old switch.  I don’t know about the legality but you could replace it with a toggle switch and a 3A in line fuse.

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8 hours ago, Teddyhherrera said:

Sorry to rehash an old thread but...

New pilot, 1975 M20f. Recently had a mid air total avionics failure, 375, 430, stormscope, engine monitor all shut off. Upon turning the avionics switch off and on they came back on for about a second and died again. 

Locql avionics shop said it was a relay. But according to the internet and you guys, it should have failed on. Are they misdiagnosing this or is it plausible? 

Look further up on the thread, December 3, 2017, Jack46's post. Exact same thing happened to him.  I would listen to your shop. 

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If it affected all the radios, it pretty much has to be the relay. The relay is normally closed to power the radios if the radio master switch or wiring, or the coil in the relay fail. The radio master is wired to power the relay and turn the radios OFF when the switch is on the OFF position. 

This setup protects against a failure of the relay coil, but does not protect against a failure of the relay contacts or operating mechanism.

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