What size fuse for Cessna Clock?

On my clock, Cessna p/n C-664-08-0101 It has a contact points and a solenoid
inside. The points come together and the solenoid will the ratchet a spring
loaded gear and open the points at the same time. The spring pulls the gear
around, which drives the clock till the points make contact again. This
process is repeated each minute. There is no motor and current draw is only
while the points are closed and the solenoid is energized. My .02 cents
worth. Hope this helps. A story concerning fuse replacement, I suggest you
not guess at the fuse. The circuit is hot at all times (master off) in
order for the clock to work. In 1964 my friend and I was using his Dad' new
Chevy pickup. One night the dash lights failed (it had nothing to do with
the girls we had with us) and the tail lights and dash lights are on the
same fuse. We had taken the vehicle to our local garage, and they replaced
the fuse. The next morning the inside of the pickup was on fire, the
vehicle was a total lost. The insurance company, stated that this was a
common fault with the wiring on this model vehicle and just bought a new
one. I had noted that the replacement fuse was .25 amps larger than the
original. The mechanic stated, if you have a short it will blow. The fuse
had not blown, the red wire from the battery + post going into the wiring
harness and through the firewall had melted. The fire had started under the
dash. Lesson well learned.
Clyde

"George Patterson" wrote in message
news:zxNee.56$Dn.52@trndny02...
nrp wrote:
I suggest 1 Amp as the OEM clock is an occasional very short but sharp
current pulse type of load.

Say what? It's got a little motor in it. Current draw is constant.

George Patterson
There's plenty of room for all of God's creatures. Right next to the
mashed potatoes.

That's that's the OEM clock I have. Just between us girls, mine only
ran about 10 years before it hung. I opened it up, washed it out in
solvent, and reoiled with 15W50 Mobil 1 oil. It's been keeping good
time for about 15 years now.

They have a really clever mechanism in them that adjusts the speed very
slightly as you adjust the hands of the clock. If you have to keep
advancing them, it speeds up etc.

Are you sure it (the replacement fuse) wasn't 25 amps bigger? It is
hard to imagine a fire being started from a measley (sp?) 250
milliamps..........

If you take a look at the current pulse during the solenoid pop, you will
find that it is just a little bit over 250 mA (0.25 amp) during the tug, but
the current only flows for a quarter of a second or so.

I recommend a "slow-blow" type fuse for the application where the current
has to exceed the rated current for some period of time before it blows.
The amount of time is dicatated by the amount of current. A short circuit
of ten amps or so will pop it in a few milliseconds, yet it will hold half
an amp for a couple of minutes.

The slow-blow gives you the best of all possible worlds with pulsed current
like this.

See also the Kitplanes article on making your own LCD clock with a Rat Shack
module. Current draw is something on the order of half a milliampere.

Jim



"nrp" wrote in message
ups.com...

Jim -
No apologies to the guy you torpedoed out of the water a few posts ago, but
who came out being pretty close to the mark????

Huh?

Jim


"Greg Farris" wrote in message
...
Jim -
No apologies to the guy you torpedoed out of the water a few posts ago,
but
who came out being pretty close to the mark????