Charging System Gremlin

I have a vexing problem on my 1979 Warrior. The charging system will
shut down in flight at random times. The ammeter drops to 0 and the
idiot light comes on. A recycling of the ALT switch may stop the
problem but it may happen several more times before "settling down".
There is NO pattern to the shut downs. They cannot be correlated to
electrical load, length of flight, weather conditions, time of day,
IMC/VMC, number of passengers, or the color of the clothes I am
wearing. It may not happen for months, then occur without warning.
The alternator, voltage regulator, and battery are all relatively new
(1-2 yrs old).

We have had the FBO look at this several times. Of course it doesn't
happen when its in the hangar during run-up!! One time they said the
field terminal on the alternator was loose and they tightened it down.
That seemed to stop the gremlins but it has cropped up again. The FBO
now reports "no problem found".

Of course if the charging system shuts off and stays off, this is what
I would call "bad news"...especially in IMC. So far its just been an
annoyance and my pulse no longer jumps to 150 when I see the charging
warning light come on.

Any ideas on what could be causing this?

Thanks!!!

--Jeff

Your OverVoltage Relay (OVP) is tripping spuriously, shutting down the
Alternator Controller in flight. This has been delt with on
rec.aviation.* many times. Please use this to find all of the previous
traffic:

http://groups.google.com/advanced_search?q=&hl=en&

put "overvoltage relay trip alternator " in the ALL THE WORDS BOX
and put "rec.aviation.*" in the GROUP box

Your answer is there. Write back if you need additional.

MikeM


wrote:
I have a vexing problem on my 1979 Warrior. The charging system will

Thanks for the pointers. Lots of good stuff. What I don't see is the
kind of RANDOM OVP trips that I've encountered. It really is
random...fine for months then maybe a flurry of shutdowns. Maybe at
the beginning of a x-c flight and then its fine, or maybe at the end.
And since it doesn't occur on the ground or at predictable times
(naturally!), I've got few options for methodically tracking it down.

I've thought about just letting it go until it becomes more frequent
(and predictable) but I worry that will occur in solid IMC.

I notice that its often traced back to a faulty/corroded master switch.
Any other ideas?

--Jeff

Having the battery on line helps stabalize the bus against voltage
spikes of various kinds.

So things that put resistance between the bus and the battery
defeat this purpose. Corrsosion on connections is a suspect.
If this has the master solenoid with big terminal bolts on it,
loosen each nut and tighten the stack of nuts starting at the insulator
block.
Often the pheonolic insulator block shrinks and that make the
path from the wires to the contacts flakey.

Low water level in the battery also dramatically increases its
internal impedance level, leading to the same result.

Bill Hale

Importing the ideas from the Cherokee chat.. (piperowners.com) - If
you are not a member you REALLY should be!

----- This has been traced to the bad contacts in the master switch
so many times I would change it before looking for anything else,
unless the (elsewhere) fault was obvious..

Cheers & good luck!

Dave

On 3 May 2006 16:48:57 -0700, "
wrote:

Having the battery on line helps stabalize the bus against voltage
spikes of various kinds.

So things that put resistance between the bus and the battery
defeat this purpose. Corrsosion on connections is a suspect.
If this has the master solenoid with big terminal bolts on it,
loosen each nut and tighten the stack of nuts starting at the insulator
block.
Often the pheonolic insulator block shrinks and that make the
path from the wires to the contacts flakey.

Low water level in the battery also dramatically increases its
internal impedance level, leading to the same result.

Bill Hale

writes:

Thanks for the pointers. Lots of good stuff. What I don't see is the
kind of RANDOM OVP trips that I've encountered.

Have you cleaned every ground, tightened every connection, wiggled
every wire looking for one that looks good, but.....?



--
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

You should test the OVP module itself.

Remove it from the aircraft.

On the workbench, connect it to a well-regulated adjustable DC power
Supply capable of delivering 3A Plus to OVP Input and frame ground.
Use a good quality Digital Voltmeter across the supply to measure the
voltages described below:

Connect a 12V 1156 automotive turn-signal lamp between the OVP Output
and ground (two lamps in series if your aircraft is 28V).

Starting with the supply set to 12V (28V), the lamp(s) should be on.

Slowly turn up the voltage. The lamps should go off when you reach
15.5V (31V).
If at that point, you begin reducing the voltage, the lamps should stay
off even as you reduce the voltage down below 5V (10V). The OVP has
"Tripped".

You have to momentarily turn off, or disconnect the supply and start
with the voltage set below the cut-out voltage to get the lamps back
on. "Reset" the OVP.

Set the supply to about 14.5V (29V) with the lamp(s) on. Rap on the OVP
with a screwdriver handle to see if vibration will induce premature
tripping. If so, replace it.

If the cut-out occurs less than 15.5V (31V), you may wish to adjust
the OVP so that the trip point is 15.5V or slightly higher.

Good luck.

I do not own a Piper, but I seem to remember the OVR is under a seat.
Some past poster was mentioning shorting to the seat.

I have a Cessna and had problems and it was a faulty masterswitch.

Ross
KSWI

wrote:

Thanks for the pointers. Lots of good stuff. What I don't see is the
kind of RANDOM OVP trips that I've encountered. It really is
random...fine for months then maybe a flurry of shutdowns. Maybe at
the beginning of a x-c flight and then its fine, or maybe at the end.
And since it doesn't occur on the ground or at predictable times
(naturally!), I've got few options for methodically tracking it down.

I've thought about just letting it go until it becomes more frequent
(and predictable) but I worry that will occur in solid IMC.

I notice that its often traced back to a faulty/corroded master switch.
Any other ideas?

--Jeff

My '74 Archer's OVP is on the left sidewall under the instrument panel. I
used to get mysterious tripping of my OVP and finally realized it would trip
sometimes when I was using the electric trim. A good lubrication of the
trim system during an annual greatly improved the situation.

--
Best Regards,
Mike
http://photoshow.comcast.net/mikenoel
"Ross Richardson" wrote in message
...
I do not own a Piper, but I seem to remember the OVR is under a seat. Some
past poster was mentioning shorting to the seat.

I have a Cessna and had problems and it was a faulty masterswitch.

Ross
KSWI

wrote:

Thanks for the pointers. Lots of good stuff. What I don't see is the
kind of RANDOM OVP trips that I've encountered. It really is
random...fine for months then maybe a flurry of shutdowns. Maybe at
the beginning of a x-c flight and then its fine, or maybe at the end.
And since it doesn't occur on the ground or at predictable times
(naturally!), I've got few options for methodically tracking it down.

I've thought about just letting it go until it becomes more frequent
(and predictable) but I worry that will occur in solid IMC.

I notice that its often traced back to a faulty/corroded master switch.
Any other ideas?

--Jeff

BTW, I have an over voltage protection relay for
Cherokees in my stash of stuff. Be happy for it
to have a new home.

Bill