Master switch replacement

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elliotblock
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Master switch replacement

Post by elliotblock » Fri Mar 13, 2020 9:27 am

I got through adding ADS-B, an intercom, and bose jacks to my airplane so she is flying again!

One remaining issue is the master switch. It is intermittent. I believe this was caused over time by the contacts of the switch arcing since (up until now) there was not a fly back diode at the battery contractor.

So the question is... how can I remove the master switch?

I’m hoping someone will tell me it’s easier than it looks, but I don’t think it will be. First I think I need to remove the fascia plates in front of the radio stack and glove box which will expose a screw on each side backed by a nylock.

From there does anyone have any tips?

Thanks
Elliot
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2356
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Re: Master switch replacement

Post by 2356 » Fri Mar 13, 2020 10:38 am

Are you sure the contactor/solenoid on the battery box is not your problem?

8474
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Re: Master switch replacement

Post by 8474 » Fri Mar 13, 2020 5:46 pm

I see you have an A model. I have just been doing a lot of rewiring and switch work in my A model. The easiest ( maybe only) way to access those switches is removing the instrument panel. Then you can see down and do most of the work from up top. Those switches are simple toggle switches that go thru a hole on the piano key to move them. The master switch is different from the rest, my parts book says it is AN3027-1 The inoperative piano keys are simply held stationary by a bolt, you remove that bolt and install a switch in its place. I did that and now have a Radio Master switch. I still have one unused piano key and if I ever do an ALT conversion I will make that my ALT switch.

elliotblock
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Re: Master switch replacement

Post by elliotblock » Sat Mar 14, 2020 10:55 am

2356 wrote:
Fri Mar 13, 2020 10:38 am
Are you sure the contactor/solenoid on the battery box is not your problem?
Unfortunately, yes I’m sure. But thanks for trying to save m me a lot of work :D .

elliotblock
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Re: Master switch replacement

Post by elliotblock » Sat Mar 14, 2020 10:58 am

8474 wrote:
Fri Mar 13, 2020 5:46 pm
I see you have an A model. I have just been doing a lot of rewiring and switch work in my A model. The easiest ( maybe only) way to access those switches is removing the instrument panel. Then you can see down and do most of the work from up top. Those switches are simple toggle switches that go thru a hole on the piano key to move them. The master switch is different from the rest, my parts book says it is AN3027-1 The inoperative piano keys are simply held stationary by a bolt, you remove that bolt and install a switch in its place. I did that and now have a Radio Master switch. I still have one unused piano key and if I ever do an ALT conversion I will make that my ALT switch.
I was worried this might be the case...

I’ve actually got a surplus of switches as the turn and bank switch is installed but not connected to anything (venturi air is being used for an aftermarket turn and bank).

I’ve got the radio master switch.

Now I’ll have to formulate a game plan.

Thanks!
Elliot

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6643
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Re: Master switch replacement

Post by 6643 » Sat Mar 14, 2020 11:37 am

The master switch is going to be a double pole (two circuits) single throw switch. The other set of contacts is for the generator field.

If you switch to an alternator, the best setup is an interlocked switch that allows you to have the Master on and the alternator off, but not the other way around. That said, you have to follow the STC. Bottom line, you never want to have the master off with the alternator still on, but you want to be able to switch the alternator off with the master still on.

8474
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Re: Master switch replacement

Post by 8474 » Sat Mar 14, 2020 11:41 am

Other than having to disconnect the pitot/static lines, tach cable, etc, taking the instrument panel out is pretty easy and really give access to the switches. I also converted all the old fuses over to breakers.

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