OK, lets make that BREAK instead of bread.


-------------
Regards, Ross
C-172F 180HP
KSWI


Ross Richardson wrote:
I would check all the grounds in the system. That can cause this
problem. Along with a bad alternator switch. It causes the VR to not
work properly. I had to bread each connection, clean it, then re-do it.


-------------
Regards, Ross
C-172F 180HP
KSWI


Jay Honeck wrote:

Of course, we have a new squawk shortly after coming out of the shop.
Perhaps someone here can point me in the right direction?

Here's the scenario with our 1974 Piper Cherokee Pathfinder, with a
530 hour, normally aspirated Lycoming O-540-B4B5 engine:

1) Flying to Janesville, WI today. Extremely cold -- around 15
degrees Fahrenheit on the surface, near zero at altitude. The first
real cold snap of the year.

2) In steady-state flight, both of us hear a "woo--woo--woo..." softly
in the headphones. It sounds just like strobes that aren't grounded
properly.

3) The noise slows down -- or speeds up -- in synch with the prop
RPM. At 2300 RPM, it's going a bit faster than once per second --
maybe around three times every two seconds.

4) I switch our digital voltage/amperage meter to AMPs, and watch as
it oscillates in time with the noise. It's alternating from 5 amps to
10-11 amps, in time with the "woo--woo--woo"... Voltage appears to
be pretty steady at around 13.8-ish volts.

5) Adding load to the system (landing lights, fuel pump, etc.) makes
the noise louder. Adding load to the system and then suddenly turning
everything off makes the noise and amperage oscillation go away -- for
about 30 seconds. It then returns.

6) Turning the alternator side of the split master switch ALSO makes
the noise go away. It sometimes stays away when I turn the
alternator back on. Sometimes it doesn't.

7) The battery is new this past summer.

So, we've got a noise and amperage indication that can be corrected by
adding load to the system -- and then suddenly taking it away. The
noise is also fixed -- sometimes -- by cycling the alternator off and on.

The service last week was having the impulse couplings serviced (per
service bulletin), so electrical things have been tinkered with since
our last flight. (This is ALWAYS when some new squawk seems to crop up.)

Any ideas? Loose ground wire somewhere? Alternator failing? Any
and all input is welcomed!

Thanks!