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Electrical issue M20J - Need Help Please

N177MC

By N177MC
in General Mooney Talk

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DonMuncy Grand Master

DonMuncy

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It is not legal for me to wire things onto my plane (outside the owner maintenance list), so if I need something like that done I make a note on my wish list, and later I find it has mysteriously been done by my hangar elf.

DonMuncy Grand Master

DonMuncy

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He works on a "don't ask, don't tell" basis.

I am not smart enough to know how to post pictures here, but in my photo gallery is a photo of my elf I snapped when I snuck out to the hangar late one night.

Alan Fox Grand Master

Alan Fox

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Both the Master switch and the Avionics switch went off line on take -off just as the gear was finishing retracting. The INST LTST breaker also popped .

 

This is a '76  M20J and it's the 3rd time - on all three occasions  the battery had been very low and the plane was started with an auxiliary external battery.

 

I'm thinking it might be a gear up limit switch out of adjustment but don't understand the correlation between that and the low battery/high charge situation not the INST LTST breaker blowing.

 

Any trouble-shooting help much appreciated !

76 ?????? J ???????

N177MC Community Regular

N177MC

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Okay, I was not aware of that.  

 

BTW: This is the model with the "Piper" engine control quadrant.

 

Thanks !

fantom Grand Master

fantom

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Okay, I was not aware of that.  

 

BTW: This is the model with the "Piper" engine control quadrant.

 

It helps you and everyone else to indicate your model and year somewhere in your signature block. Location would be a bonus.

 

Makes questions easier to understand and answer.

N177MC Community Regular

N177MC

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Sure, but I'm an A&P and I "look after" a 201, an Ovation II and a Screaming Eagle so I would still have to call out the model type & year on every post. 

bnicolette Veteran

bnicolette

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The Battery MINDer comes with a harness that is not considered permanently attached and doesn't even need a logbook entry.  I connected mine to the battery and routed it through an existing hole in the baggage area bulkhead and had it come out from behind the interior panel.  I connect to it through the baggage door, which can be closed and locked carefully if you wish.

 

I have mine coming out right at the ground power receptacle.  When not in use they fit within the receptacle very nicely.

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KSMooniac Grand Master

KSMooniac

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That is a perfect solution!  Unfortunately my J did not come with the GPU receptacle option... I might eventually add it and then will re-route the battery minder harness like you did.

 

I have an early '77 J as well (with that damned throttle quadrant that isn't long for this world in my plane!) and I believe it was assembled and maybe even delivered in Dec '76, but never listed as a '76 model J as they were all sold as '77 models as far as I understand.

N177MC Community Regular

N177MC

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Back to my original problem: What exactly is going off line and shutting the general electric circuit down ?  I would assume there is a normal solenoid relay, but don't have the schema in front of me.  Also, could the avioincs Master trip the Master switch ?

 

Thanks !

Marauder Grand Master

Marauder

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That is a perfect solution! Unfortunately my J did not come with the GPU receptacle option... I might eventually add it and then will re-route the battery minder harness like you did. I have an early '77 J as well (with that damned throttle quadrant that isn't long for this world in my plane!) and I believe it was assembled and maybe even delivered in Dec '76, but never listed as a '76 model J as they were all sold as '77 models as far as I understand.
You don't like your quadrant?! When I am flying mine I feel like I should be calling out V speeds! :)
KSMooniac Grand Master

KSMooniac

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You don't like your quadrant?! When I am flying mine I feel like I should be calling out V speeds! :)

No, I really don't, but it obviously wasn't a big enough problem to pass over my wonderful J.  It is imprecise and takes up a lot of volume right where my knees are, especially getting in and out.  It was a marketing gimmick that Mooney and Piper did in the 70s and thankfully Mooney switched back to conventional precision controls in '78.  I bet the quadrant assy is heavier too... I'll weigh everything when I make the swap.

Hank Grand Master

Hank

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Back to my original problem: What exactly is going off line and shutting the general electric circuit down ?  I would assume there is a normal solenoid relay, but don't have the schema in front of me.  Also, could the avioincs Master trip the Master switch ?

 

Thanks !

 

What's going on is that too large of a load is being applied to your electrical system. The alternator is charging the battery at ~30 amps; the gear motor is pulling 20-25 amps. Then you have radios, GPS, lights, etc. Overload! Things shut down.

 

Electricity is not like a gear train, where the jam can be precisely located and an exact cause found and remedied. Strange things happen, because electricity isn't logical to my mechanically-oriented brain. Overload the system, or get close to it's limit, breakers will pop and things will turn off. I had a bare spot on my landing light wire that rubbed on the cowl that would randomly reset the avionics [G430W and King Com2 & Nav2], wiping the King's memory and setting it to 120.00 while the Garmin was rebooting. No breakers tripped, no circuits popped, but lost the radios all at once anyway. Looked for stuff, wrapped the wire to the light, no more problem.

 

Electricity is weird. Buy a Concorde dry cell, don't let it discharge, these types of things should stop.

 

P.S.--I like my throttle quadrant!!

N177MC Community Regular

N177MC

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I had a look at the wiring diagram and indeed, there is a battery solenoid relay (just like every other GA ship !) and I suspect that it simply collapses from lack of sufficient voltage, thus shutting down the electrical system .

 

What I'm not sure about is whether the Master switch needs to cycled or reset to bring the solenoid relay back online and same for the Avionics Switch ?

 

I suspect that the Master does not have to be reset but the way the Avionics Master relay appears to be set-up I suspect it needs to be recycled.

Alan Fox Grand Master

Alan Fox

Posted
Posted
I had a look at the wiring diagram and indeed, there is a battery solenoid relay (just like every other GA ship !) and I suspect that it simply collapses from lack of sufficient voltage, thus shutting down the electrical system .

 

What I'm not sure about is whether the Master switch needs to cycled or reset to bring the solenoid relay back online and same for the Avionics Switch ?

 

I suspect that the Master does not have to be reset but the way the Avionics Master relay appears to be set-up I suspect it needs to be recycled.

The avionics master is not really a switch , its a circuit breaker , it actually closes the avionics master relay when it trips....Meaning it doesnt turn on the avionics bus , The avionics bus is on a normally closed contactor , and when you select off it powers up the contactor and opens up the avionics bus......(if it fails the avionics stay on)...

  • 3 weeks later...
  • 3 months later...
dcastor Collaborator

dcastor

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I have mine coming out right at the ground power receptacle.  When not in use they fit within the receptacle very nicely.

 

Bnicolette: that looks like an SAE connector, you haven't had any issues from IAs about having automobile wire on your airplane?

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