Landing Light CB

Landing light circuit breaker 20 amp. Pops after about one minute.
I have changed the landing light 4552, changed the CB and thought I had the
problem solved.
This morning Taxi at 6 am (still dark) I was pleased to have the landing light
while in close quarters, then the CB popped.
I have checked the wiring and connections and everything looks good.
Will go with my trusty amp meter and see what the bulb draws.
In the meantime can any one give some advise.
The plane is a C 172 with the Avcon conversion.
Thanks
Hank

Hankal wrote:

In the meantime can any one give some advise.

My guess is a bad ground for the landing light.

George Patterson
If you want to know God's opinion of money, just look at the people
he gives it to.

Hankal wrote:

In the meantime can any one give some advise.

If you are stationary and not in transit and engine off, does it still
trip the breaker? If not, sounds like a chaffed line that might be
shorting out somewhere along its path to the light - from the switch...

Darrel Toepfer wrote:

Hankal wrote:

In the meantime can any one give some advise.

If you are stationary and not in transit and engine off, does it still
trip the breaker? If not, sounds like a chaffed line that might be
shorting out somewhere along its path to the light - from the switch...

Unless it's an erratic short caused by vibration, that will result in the immediate
tripping of the breaker. Sounds to me (as someone else also said) that something's
heating up and causing the delayed trip. In my experience, that's frequently caused
by a poor ground connection.

I do agree with you that the problem is between the breaker and the light ground
connection. Could also be the switch.

I usually troubleshoot these things by moving the load further up the circuit until
the problem disappears. At that point, I've isolated the problem. In this case, I
would use sandpaper to polish the ground connections. If that didn't correct the
problem, I would remove the bulb, attach temporary leads, and hook it up directly to
the switch. If the breaker doesn't trip after a reasonable period of time, the
problem is in the wiring to the light fixture. If it trips, disconnect the switch and
hook the light up to the switch wire. If the breaker doesn't trip, the switch is the
problem. And so forth.

Now. If you wind up with the light hooked directly to a brand new breaker and the
breaker trips, I would be somewhat at a loss.

George Patterson
If you want to know God's opinion of money, just look at the people
he gives it to.

"G.R. Patterson III" writes:



Hankal wrote:

In the meantime can any one give some advise.

My guess is a bad ground for the landing light.

Huh? At worse, a bad ground will lead to little/no lamp output.

I suspect a chaffed/worn wire between the breaker and the lamp.
Usual technique is to put a test lamp in series, at the breaker.
Then wiggle/twist/gently yank/ the wiring. When the test lamp goes
to full brillance; you've found the short.

The trouble here is the landing lamp will pull so much current that
you'll need to use a similar lamp for the tester. Your old one
would do.


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

That lamp is a 250 watt lamp and should draw 9 amps.
If you are popping a 20 amp breaker you have a wire that is shorting
to chassis somewhere. Turn the light on shake the wires and tap with
a rubber mallet along the wire's route till the breaker pops. Some
where that wire runs over a sharp metal edge.

On 20 Aug 2004 23:34:19 GMT, (Hankal) wrote:

Landing light circuit breaker 20 amp. Pops after about one minute.
I have changed the landing light 4552, changed the CB and thought I had the
problem solved.
This morning Taxi at 6 am (still dark) I was pleased to have the landing light
while in close quarters, then the CB popped.
I have checked the wiring and connections and everything looks good.
Will go with my trusty amp meter and see what the bulb draws.
In the meantime can any one give some advise.
The plane is a C 172 with the Avcon conversion.
Thanks
Hank

G.R. Patterson III wrote:
Hankal wrote:

In the meantime can any one give some advise.

Now. If you wind up with the light hooked directly to a brand new
breaker and the breaker trips, I would be somewhat at a loss.

I think he needs to give me his Avcon conversion for our tried and true
Cont. 0-300D... I'll even throw in a Q-Beam... ;-)

Nobody looks it up. The 4522 lamp is usually used in a swing-down lamp. The
swing down lamp has a motor to drive the lamp up or down.

The lamp is 12 volt, 250 watt, something the guesser at 9 amps (if for a 24
volt plane) would have realized if the system voltage of the plane had been
given, so the current draw for the lamp along is a nominal 20 amps.

If the motor circuit is not opened by the switch/relay built into the light,
the combination of the lamp current and the motor current will pop the breaker
every time, in a short time.

Yes, check the amps with a current meter, and please do not let the motor run
long in the test or it will burn out.

Neal

On Fri, 20 Aug 2004 22:01:19 -0500, Darrel Toepfer
wrote:

Hankal wrote:

In the meantime can any one give some advise.

If you are stationary and not in transit and engine off, does it still
trip the breaker? If not, sounds like a chaffed line that might be
shorting out somewhere along its path to the light - from the switch...

That's my guess. Try replacing the wire.

COUGARNFW wrote:
: Nobody looks it up. The 4522 lamp is usually used in a swing-down lamp. The
: swing down lamp has a motor to drive the lamp up or down.

: The lamp is 12 volt, 250 watt, something the guesser at 9 amps (if for a 24
: volt plane) would have realized if the system voltage of the plane had been
: given, so the current draw for the lamp along is a nominal 20 amps.

: If the motor circuit is not opened by the switch/relay built into the light,
: the combination of the lamp current and the motor current will pop the breaker
: every time, in a short time.

: Yes, check the amps with a current meter, and please do not let the motor run
: long in the test or it will burn out.

: Neal

Correct... I wouldn't even go around shaking the wire, etc, checking for
chafing until I measured the current. It's awfully easy to put in a bigger bulb "more
is better" and all. A friend's Comanche had had two landing lights installed that
were *both* 250W (14v plane). That would require a 40A breaker... rather insane.
Some boob had put the wrong bulb in it, because each was supposed to be a 90W bulb
(125W? I don't recall exactly, but not 250).

Disconnect the wire at the breaker, insert ammeter, and then read the current
with and without the engine running. The change from the bulb running on 12V/24V
(engine off) to 14V/28V (engine on) makes a significant difference in current. There
should be plenty of margin on the breaker (e.g. taking 10A on a 15A breaker).
Breakers do drift a bit with age and typically can blow easier than when new. If it
is the correct bulb and within spec of the breaker, THEN look for worn wires and/or
weak breaker. Replacing the wire as the first thing is silly and a lot of potentially
unnecesary work.

-Cory
--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering Ph.D. Graduate Student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************