12 V plug...how to use

fairbanksflyer · Post by **fairbanksflyer** » Mon Mar 02, 2009 9:49 am

I have one of those 12V adapter plugs in the side of the fuselage. How do you properly use it? Don't want to fry anything. I have the plug in somewhere in the previous owners pile of stuff he gave me. Can you charge through it? Thanks

a64pilot · Post by **a64pilot** » Mon Mar 02, 2009 10:22 am

What you have is usually a 24V external power connector. Normally there are three posts with one being smaller in diameter and shorter than the other two. You do not appear to have this short post. Normally power is applied to this short post which closes a relay and connects the positive bigger post to the battery. Normally there is nothing "hot" in this plug.
I theorize that somebody installed your plug and installed it so that it is "hot" all of the time. I would use a multimeter to verify this as well as which pin is what polarity before I connected anything to it. The rubber connector that plugs into the aircraft should have external markings as to polarity molded into the plug.
If I am correct and not full of it, I would be darn sure to not plug in the start cart that you will find at most FBO's as you will be connecting 24V to a 12V system.
Of course, I may be full of it, but I don't think so.
External power connectors are good for charging, avionics tests and any electrical maintenance as you don't run the battery down and of course for jump starting the airplane after you run the battery down because you didn't use external power.

All precautions you take for jump starting your car should be taken for using external power in an airplane, like making sure your dead battery isn't frozen for instance.

fairbanksflyer · Post by **fairbanksflyer** » Wed Mar 25, 2009 9:35 am

I finally got the plug and cable assembly from the original owner. When I plugged it in (by the way, my Maule plug only has 2 large prongs) and hooked it to a battery, I immediately got power to the panel. Didn't matter that the master switch was off. Does this sound normal? Can I charge the battery this way or jump start the airplane? The plug end does have 2 large holes and one smaller one, but as I stated, the plane only has 2 prongs. Don't want to damage anything.

Sam Rutherford · Post by **Sam Rutherford** » Wed Mar 25, 2009 10:44 am

My plane has exactly the same, and the plug and cable.

I have never used it, but my understanding from the previous owner is that it's in parallel to the battery ie you can charge and jump start using it. Could be handy, just not so far as I have needed!

I would have guessed that yours is the same setup - although it's VERY odd that it short circuits your master switch. I would change that, if I were you!

Safe flights, Sam.

a64pilot · Post by **a64pilot** » Wed Mar 25, 2009 3:17 pm

A lot of airplanes like my Cessna 210 are wired so that when external power is applied to the external power connector, the master relay closes so that it acts as if you turned the master switch on. Don't know why it's done that way, but it's the way Cessna wired it.
Jeremy or Duane, did Maule install thse plugs?

UP-M5 · Post by **UP-M5** » Wed Mar 25, 2009 6:37 pm

on cessna and piper products- the POH specifies that the master switch remain turned OFF while using ground power, and stay OFF until the external power is removed. or damage may occur.
sounds like yours is similar.
do you have power at the plug when the master is off? (i'm guessing no)
how about when the master is on? (guessing yes)
if this is the case you cannot use it to charge your batt. the plug is wired in downstream of the master contactor, so your battery remains out of the circuit. it can still be used to jump start.

Duane · Post by **Duane** » Thu Mar 26, 2009 4:37 am

I cant find anything in print that would show we installed this plug. We just started about 3 or 4 years ago installing this type plug.

On our installation, the hot side is hooked up to the same terminal on the solenoid as the wire coming off the battery so the panel is only hot if you switch on the master. Can be used to charge or jump start.

TomD · Post by **TomD** » Thu Mar 26, 2009 10:56 am

A ground power service plug with solenoid was installed on my M5-235C in 1979 on a 337. I am pretty sure it is a three prong plug and I have jumper cables w/ a three prong female on it.

I am going up to my plane in an hour or so and will check it out.

TD

fairbanksflyer · Post by **fairbanksflyer** » Thu Mar 26, 2009 9:46 pm

After you mentioned the 337, I went back and checked this airplanes 337's and found this..."Installed auxiliary power plug on left side of boot cowl using AN2552 guard type aircraft 2 prong receptacle...fabricated backing plate using procedures in AC 43.13-1" I'm going to go out tomorrow and check voltage at the prongs with and without the master switch on, as suggested by UP-M5. If the airplane is "jump started" using this plug, should the master switch be off even though I have power to the panel with it off? Haven't had to do that yet, but the other day I wanted to play with the electronics with out running the battery down so I plugged in a spare 12V battery. Worked slick!.

a64pilot · Post by **a64pilot** » Fri Mar 27, 2009 9:01 am

I think that as long as your avionics master is off so that your avionics are off, that jump starting won't hurt anything. I mean your master is on when you start the airplane normally, what's the difference?
On my Cessna, the best use for the aux power plug so far has been avionics, lights etc. troubleshooting. The only time I had to jump start it, I didn't have a plug, just car jumper cables so I had to go direct to the battery.
I left the master on overnight

UP-M5 · Post by **UP-M5** » Fri Mar 27, 2009 9:56 am

when you plug in the ground power- it acts as though the master has just been turned on- even though it is OFF.
start the engine- unplug ground power- turn master switch on.

BTW- great lookin M5 fairbanksflyer

i was just up your way a week ago shooting your ILS.

fairbanksflyer · Post by **fairbanksflyer** » Fri Mar 27, 2009 10:09 am

I saw your post in the Spring Flying...where were those pictures taken?? Looks like a nice spot. My first time flying skis so I have a lot to learn about picking a spot to land that won't get me in trouble. Maule tails are heavy and I won't want to get stuck on my own. Have a tail wheel penetration ski but haven't installed it. Been landing on groomed snow so it hasn't been a factor. My first time on this forum and I'm impressed with how fast and how many replies you get...it's a great wealth of information. I'll be constantly coming back! M4-220C with Wesco AS2B "plank" skis...heavy!!

UP-M5 · Post by **UP-M5** » Fri Mar 27, 2009 6:01 pm

pics are in the hills around talkeetna. if you are in the area, stop by. if you stop by flight service, they can always find me.

fairbanksflyer · Post by **fairbanksflyer** » Sun Mar 29, 2009 12:28 am

Got my tailwheel endorsement in Talkeetna with Drew

belandd · Post by **belandd** » Sun Mar 29, 2009 5:41 pm

Did my first great ground loop at talkeetna the weekend after it was paved. I was flying a PA 20-150.
Never been on pavement before. When I touched down I reversed direction completly and shot down the runway backwards. then reversed direction again and came to a stop.

did no damage except my passenger tried to tear out the inside braces.

The final embaressment came when I walked into town to have breakfast and while i was getting coffee the waitness asked (in a loud voice) are you the guy that just ground looped that Piper? Every one there was looking at me so I burst out laughing.

that PA 20-150 taught me a lot about flying taildraggers

12 V plug...how to use

12 V plug...how to use

12v plugin

Ground power

337 on aux 12V plug

spring flying

Talkeetna

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