is there a non-switched power wire available on panel?

[NicoN]

We have a Astrotech LC-2 clock in our Panel . it is battery powered and works.

But it seems to have a rather high power comsumption. 2 batteries were drained within 3 weeks each.

So, I am thinking of powering the clock from the battery.

This would require a continously powered wire which is not switched with the master.

I did not find such a wire in my wiring diagram.

Did I miss something? Otherwise there  must be such a wire, because there is cabin lighting which can be switched off and on independently  from the master.

[BDPetersen]

Those clocks seem to Ron forever on battery. May be a clock issue.

[NicoN]

Okay. I have that experience too.

 

[LANCECASPER]

On my M20M there’s an always hot wire that goes to the clock. The LC2 clock is notorious for going bad.

[EricJ]

If it's draining the batteries, which I believe should last a year or two, there's probably something wrong with it and I sure wouldn't hook it up to ship's power or the airplane may wind up with a dead battery.

There are two kinds of LC-2;  the independent kind (like yours) powered by a small, replaceable battery, and the kind that just wires directly to ship's power, like mine, and draws something like a microamp.

I just went through this as part of my avionics installation.   I had a dead LC-2 in the panel and the shop replaced it with something that they had lying around that connected to switched ships power but had it's own battery for backup.   It drew about a quarter of an amp even with the master off and left my battery dead a couple of times until I figured out what was going on.

So my LC-2 got rehabbed and during one of my warranty stops back to the avionics shop they put it back in.   Clock works great, battery stays fine.   I had measured its current draw and it's peanuts.   Those little LCD circuits take almost no power to run.

Also, if you want to power your battery-powered LC-2 with ship's power you'll have to make a regulator that drops the 12V or 28V in your airplane down to the battery voltage that your clock is expecting.   I think it's either 1.5V or 3V, I don't remember whether it has one or two AAA batteries.    And, yes, there should be one wire going to the LC-2 for the backlight, but that's it if it's battery powered.

I would suggest taking it out and maybe handing it over to a hangar fairy or somebody that can give it a going over.   It may just need some cleaning or a capacitor replaced or something like that.   I think it's telling you there's something wrong with it.

Edited August 31, 2018 by EricJ

[ArtVandelay]

The power drain is supposed to be less than .003 amps, I would disconnect the battery and put an ammeter (multimeter) and check the current draw. Maybe it’s something else like the cabin lights.

[NicoN]

Sorry for my english. You may have misunderstood my posting.

It is the AAA battery-cell inside the clock which is empty in an unsusual short period of time - the aircraft battery is fine.

The clock was considered not working for years. I changed the battery twice now within 3 months and the clock works for a few weeks.

i think, i take it out to my bench and try to measure the power consumption.

But it may have another defect.

 

[BDPetersen]

The battery version in my Christen Eagle still runs after 7+ years. I know, it’s a miracle. Maybe the occasional 7G’s helps. ( No, not me. My son.)

[carusoam]

The K has a pretty complex wiring diagram...

Expect that there are hot wires in all modern Mooneys

1) the master switch has a hot wire leading to it...

2) Some cigarette lighters are also hot all the time...

3) a handful of Mooneys have interior lights that can be left on until the battery dies....

4) Some instrument’s with memories like radios and Fuel data have power all the time...

5) this same question has come up recently.  Somebody was looking to mount a new clock...

How is that for ideas?

PP thoughts only, not a mechanic...

Best regards,

-a-

[NicoN]

We have those interior lights which are definitively hot-wired!

The cigarette-lighter is on dependant from master.

The hot-wire which goes to the master sounds good. i will chekc that out

 

the question is also what can be done to the clock, as it should consume nearly no power, but my is eating batteries

[ArtVandelay]

We have those interior lights which are definitively hot-wired!
The cigarette-lighter is on dependant from master.
The hot-wire which goes to the master sounds good. i will chekc that out
 
the question is also what can be done to the clock, as it should consume nearly no power, but my is eating batteries

Pull it and do the bench test first, measure the drain on the battery. Once you’ve done that, I would call the manufacturer and go from there.

[David Lloyd]

Just for future thought: Most master switches are a ground source for the master relay that already has a power source to it.  Starter switches do have power from the buss and will provide power to the energize already grounded starter relay.

Edited September 1, 2018 by David Lloyd
add energize

[ArtVandelay]

Just for future thought: Most master switches are a ground source for the master relay that already has a power source to it.  Starter switches do have power from the buss and will provide power to the already grounded starter relay.

And why is that?

[N231BN]

And why is that?

Simplified wiring. There are two fuses back by the battery box. One is the hot wire to the relay and the other is the clock/cabin lights wire. If you sent the power to the switch first you would have an extra and unnecessary wire going back to the relay.

To the OP, don't use the master switch to power the clock. There should be a wire back there already for that. If the Astrotech isn't made for ship power get a Davtron that is. Or, have the Astrotech repaired so it doesn't eat batteries.

[EricJ]

5 hours ago, NicoN said:

the question is also what can be done to the clock, as it should consume nearly no power, but my is eating batteries

Somebody good with fixing electronics should be able to look at it.   There is almost nothing to it;  a small circuit board, some metal contact switches, the display, and a small integrated circuit to run the clock.   There are a few discrete parts like small capacitors and resistors and maybe a configuration jumper.    In other words, there isn't much there to go wrong, so if it is fixable it may be easy to figure it out.   It may be as easy as some corrosion developing between a few contacts that needs to be cleaned off.

 

[David Lloyd]

3 hours ago, teejayevans said:

And why is that?

A chafed wire for the master switch could short to ground and turn things on.  If wired with power, a chafed wire could short to ground and pop a fuse or breaker turning everything off.

The starter switch if shorted would pop a breaker.