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Maule’s electric wiring gotchas.

Posted: Sat Jun 18, 2022 7:39 pm
by Cash
My M7 235B has a wiring problem done at factory. The mag/starter switch bat side comes from a breaker that also feeds the done light, panel dimmer, and stall light. Guess what happens if you get a short or what ever in one of these unnecessary for flight items like the dome light that pops the breaker? You can not start the airplane! Has anyone rewired the mag/starter switch with a single wire through its own breaker? My IA is ok in doing that and can’t believe Maule wired it this way. Les

Re: Maule’s electric wiring gotchas.

Posted: Sat Jun 18, 2022 10:16 pm
by asa
Clearly you are only trying to start the engine to taxi it to a maintenance facility to fix the short circuit.... right? Seems less like a problem and more like Maule built in a checks and balances system to ensure you're following 91.213. They're super thoughtful with things like that :wink: :lol:

Re: Maule’s electric wiring gotchas.

Posted: Sun Jun 19, 2022 6:11 am
by Cash
Clearly you realize not all Airplanes are always on an airport with a A&P.

Re: Maule’s electric wiring gotchas.

Posted: Sun Jun 19, 2022 8:11 am
by Andy Young
Clearly not everyone recognizes attempts at humorous light sarcasm. ;-)

Re: Maule’s electric wiring gotchas.

Posted: Sun Jun 19, 2022 10:06 am
by Cash
Sorry ASA and Andy that I missed the humor in the post. However when this problem showed its ugly face to me, I was at a remote private strip without an amp meter nor electric wire to jump the mag/start switch must less the electric schematics that showed the possible problem. Was it a bad battery that was fully charged yet now only enough power to bring up the gages etc or was it the starter solenoid or starter? A major problem that was anything but funny. In hind site it it could be considered funny how Maule wired the Mag/starter switch. My Cessna has a dedicated circuit to switch. Again sorry. I must be still upset about the problem it caused me and when I think about the places a Maule is used by most this could be a major problem to others.

Re: Maule’s electric wiring gotchas.

Posted: Sun Jun 19, 2022 12:16 pm
by Andy Young
No worries on my part. I’ve occasionally misread the humorous intent in a comment.

You bring up an interesting potential liability that I do want to dig into, next time I get a chance to look at the wiring diagram.

Re: Maule’s electric wiring gotchas.

Posted: Sun Jun 19, 2022 9:27 pm
by asa
While I was choosing my CB's and wire sizes for my rebuild, I noticed this in the wiring diagram. It's odd but I'm assuming Maule just treated it as a "miscellaneous" circuit breaker without much thought into that failure mode. They do some funny combinations in others as well, but without the potential ramifications.

Things like this make me think it could be beneficial to carry a PDF of the wiring diagram on my ipad or phone.

Re: Maule’s electric wiring gotchas.

Posted: Sat Jul 02, 2022 2:27 pm
by Cash
That’s what I did ASA for quick reference from where ever. My M7 now has a dedicated wire and breaker from bus bar to start/mag switch. In my case some way the wire to stall light got loose and popped breaker eliminating the possibility of starting the plane. However it could have been the dome light or pesky dimmer switch having the same effect. I just wonder how many Maule models have the same wiring.