Voltage regulator contacts

(Michael) wrote in message . com...
I have a problem. Both of my voltage regulators seem to have failed
in an identical manner.

I have old-style three-relay regulators - one overvolt cutout, one
overamp cutout, and one contactor to connect the armature lead to the
bus. I can't replace these with solid state because none is available
- these are paralelling regulators, with a fourth tab that hooks into
a paralelling relay. I can't use them, either.

Seems that the contacts on the overvolt cutout have become degraded in
some way. Instead of essentially zero resistance (with closed
contacts) I'm seeing about 30 ohms. Cleaning the contacts with some
1000-grit sandpaper restores the zero resistance - and fixes the
generator problem, for a few minutes. Then the generators go offline
again, and upon testing, the resistance is back to where it was.

Anyone know a fix and/or the reason this happens?

Sounds like the silver is gone off the contacts. I wonder if a
bit of silver solder was applied and filed for contact profile?

Dan
Michael

Michael,

I had a problem on a 56 172 where the regulator went out after three months.
We found that on the master, there were a set of contacts for the field
circuit that were bad. Replaced the master switch and no more problems. May
or my not apply to you plane.

On my '65 Skyhawk, I was having lots of problems with regulator/alt. The
Cessna designed switch is terrible. Contact resistance is too high and
if you look at the switch inside you can see wear and contamination. A
good military DPST toggle would be a good choice.

Larryskydives wrote:

Michael,

I had a problem on a 56 172 where the regulator went out after three months.
We found that on the master, there were a set of contacts for the field
circuit that were bad. Replaced the master switch and no more problems. May
or my not apply to you plane.

--
Regards, Ross
C-172F 180HP

On a possibly related subject, the load meter on our '74 Archer develops St.
Vitus dance about 25% of the time. Battery seems to charge fine, and you
can't hear any noise in the headphones, but the meter just jumps up and down
a couple of time a second. No one can figure out what the problem is. The
shop boys say that they see it a lot in Cherokees, and that they have seen
replacing the master switch cure it. Any other ideas?

--
Bob (Chief Pilot, White Knuckle Airways)


"Ross Richardson" wrote in message
...
On my '65 Skyhawk, I was having lots of problems with regulator/alt. The
Cessna designed switch is terrible. Contact resistance is too high and
if you look at the switch inside you can see wear and contamination. A
good military DPST toggle would be a good choice.

Larryskydives wrote:

Michael,

I had a problem on a 56 172 where the regulator went out after three
months.
We found that on the master, there were a set of contacts for the field
circuit that were bad. Replaced the master switch and no more problems.
May
or my not apply to you plane.

--
Regards, Ross
C-172F 180HP

That is exactly what my ammeter was doing. Then one day, while the
engine was running, I reached to turn the master off. I noticed when I
touched it and rotated slightle side to side that I could make the
ammeter rock solid or dance, as you say. I had already cleaned every
point of contact that I could get to in the electrical circuit.

Bob Chilcoat wrote:

On a possibly related subject, the load meter on our '74 Archer develops St.
Vitus dance about 25% of the time. Battery seems to charge fine, and you
can't hear any noise in the headphones, but the meter just jumps up and down
a couple of time a second. No one can figure out what the problem is. The
shop boys say that they see it a lot in Cherokees, and that they have seen
replacing the master switch cure it. Any other ideas?

--
Bob (Chief Pilot, White Knuckle Airways)

"Ross Richardson" wrote in message
...
On my '65 Skyhawk, I was having lots of problems with regulator/alt. The
Cessna designed switch is terrible. Contact resistance is too high and
if you look at the switch inside you can see wear and contamination. A
good military DPST toggle would be a good choice.

Larryskydives wrote:

Michael,

I had a problem on a 56 172 where the regulator went out after three
months.
We found that on the master, there were a set of contacts for the field
circuit that were bad. Replaced the master switch and no more problems.
May
or my not apply to you plane.

--
Regards, Ross
C-172F 180HP

--
Regards, Ross
C-172F 180HP

On Tue, 3 Feb 2004 16:29:09 -0500, "Bob Chilcoat"
wrote:

On a possibly related subject, the load meter on our '74 Archer develops St.
Vitus dance about 25% of the time. Battery seems to charge fine, and you
can't hear any noise in the headphones, but the meter just jumps up and down
a couple of time a second. No one can figure out what the problem is. The
shop boys say that they see it a lot in Cherokees, and that they have seen
replacing the master switch cure it. Any other ideas?

Have you connected a to the bus while this is occuring? I bet the bus
voltage is oscillating too.

As others have suggested, a bad master switch can cause this problem.
Current flowing through the master switch cause it to heat. This
causes the contacts to deform, which breaks contact, which allows the
switch to cool, which then allows it to conduct again. Over and over
and over again.

You should get this fixed ASAP, it is definitely not good for the
charging or electrical system.

You might want to try pushing on master switch or on the panel cover
near the master switch to see if it 'amplifies' or fixes the problem.
This would confirm the need for replacement of the switch.

-Nathan

On Mon, 09 Feb 2004 23:53:10 GMT, Nathan Young
wrote:

On Tue, 3 Feb 2004 16:29:09 -0500, "Bob Chilcoat"
wrote:

On a possibly related subject, the load meter on our '74 Archer develops St.
Vitus dance about 25% of the time. Battery seems to charge fine, and you
can't hear any noise in the headphones, but the meter just jumps up and down
a couple of time a second. No one can figure out what the problem is. The
shop boys say that they see it a lot in Cherokees, and that they have seen
replacing the master switch cure it. Any other ideas?

Have you connected a to the bus while this is occuring? I bet the bus

^^^^^^^^^ Previous post should have said 'voltmeter'.