Powering up the electrical circuits on my 54'180 after complete refurb ...
All new wiring and instrument panel.
Not sure about the stall warning system ... With the circuit breaker in, the horn blares continuously and moving the stall warning vane has no effect.
Suggestions welcome ...
Thanks

The stall warning system uses a ground completion circuit. The stall warning vane (switch) has one side to ground and the other to the horn. Power is supplied to the horn. If you remove the wire which goes from the warning vane (switch) to the horn and the horn silences then the problem is with the switch. If the horn continues to sound then the problem is a short to ground of the wire going to the horn. If there is a connection at the wing root you could disconnect the wire there to narrow the search. I hope this helps.

Tim

As suggested... the stall horn is hooked up backwards.

I've had the exact issue pop up a few times on my '54 and have cured it with a very careful disassembly and cleaning. Replacement is some insane amount. little spiders seem to like the pricey real estate. Maybe spider poop is conductive, dunno.

Just to clarify, the disassembly and cleaning was not either the airplane or the spiders but was the stall switch.

It's possible that the wire from the horn to the stall vane got pinched and is shorted to ground. I would disconnect the wire from the horn to the vane first and see if the horn still sounds like previously stated. If it is silent then I would hook an ohm meter to the wire and see if it open or closed with the other end at the vane disconnected. Also a poorly crimped wire can allow a wire strand to contact the housing of the horn or vane and cause a short.

54c180 wrote:... the stall warning system ... With the circuit breaker in, the horn blares continuously and moving the stall warning vane has no effect. Suggestions welcome ...Thanks

Pull the breaker? (sorry, couldn't resist! )
As a side note, it sounds like you have the stall horn circuit on a pullable breaker?
With my 53 model, the stall horn circuit is wired from an "auto-reset" breaker which is mounted behind the panel-- in my case, adjacent to the starter button on the far left end of the row of breakers. Apparently Cessna didn't want pilots to be able to easily disable the stall warning. BTW the turn-and-bank is powered off that same breaker.

Thanks for the input everyone ... Working fine now, I look forward to the test flight.
The ground was on the wrong terminal at the stall switch.
Yes, lots of resettable circuit breakers now, completely rewired, each circuit / electric component has a breaker. Must be 25 in 2 rows and the new panel fits fine.
Slowly but surely, the end of this refurb project is in sight ...

I know it's been just over 10 years since this thread was active, but I can't find anything more recent and I currently have a possibly-related issue with the stall horn on my '54 C180.

The stall horn started coming on at random times, including in level cruise flight at 130 mph and during my pre-flight walk around with all the switches on. It eventually goes off if I flip the flap up and down enough times, but I have yet to try this after leaving the ground. I'm thinking grounding issue or crud in the switch, or both.

As an extra detail, my stall horn is wired through my nav lights, so I could shut it off if I had to, but this also shuts off my Tail Beacon ADS-B Out

flyingzebra wrote:I've had the exact issue pop up a few times on my '54 and have cured it with a very careful disassembly and cleaning. Replacement is some insane amount. little spiders seem to like the pricey real estate. Maybe spider poop is conductive, dunno.

Any chance FlyingZebra is still watching this thread and can provide a few more details about his disassembly and cleaning technique?

I just looked at the price of a new lift switch and I'm hoping I can fix this with some TLC

I would remove the stall warning switch (flapper assembly) & clean it up, and see if that helps.
I had an issue with the stall warning system on my 1953 180 a few years ago,
but as I recall the problem was actually something goofy with the horn, not the switch.

Personally I would also re-wire that stall warning system-- either put it on it's own circuit breaker,
or (more properly) reconnect it to the auto-reset breaker behind the panel that the turn & bank should also be connected to.
Here's a pic of the basic wiring diagram in my 1957 owners manual,
looks like a generator warning light (which my plane doesn't have) goes on that same circuit.

I agree with this. Most if not all vintage Cessnas have the stall horn protected by an automatically resetting circuit breaker. So, for the mechnics in the crowd, does changing the stall horn to a pilot resettable circuit breaker comply with the type design....ie, is it legal?

Of course, if you tire of hearing the stall horn, just stick a small piece of wood, such as a kitchen match in the vane to jam it up. Worked for the Border Patrol when they fitted all their old Cubs with stall horns, for "safety".

Thanks for the advice. I’ve taken the lift switch out and of course I can find nothing wrong with after testing it with a multimeter. I’m guessing there’s some corrosion somewhere and it’s sensitive to moisture, but I don’t see any non-destructive way to open it up and actually see the contacts.

The horn was wired this way when I bought it back in 2020, but I’ll see about rewiring it when I put it back, because it confused a new mechanic during my last annual.

I may also run a separate conductor back to the ground bus, rather than grounding to the airframe. I’ve heard this could help eliminate electrical ground loops, with may be causing some noise I get on my radio on certain frequencies.

SkyLarkin wrote:It's possible that the wire from the horn to the stall vane got pinched and is shorted to ground. I would disconnect the wire from the horn to the vane first and see if the horn still sounds like previously stated. If it is silent then I would hook an ohm meter to the wire and see if it open or closed with the other end at the vane disconnected. Also a poorly crimped wire can allow a wire strand to contact the housing of the horn or vane and cause a short.

Putting my panel back together trying to figure out WTF this is. Fortunately Cessna labeled the wires nicely(better than my masking tape that fell off) and I was able to figure it out. It now has a pull able CB.

'self-resetting CB'. See 2 A CB in the wiring diagram snippet previously posted.

mtv wrote:… Most if not all vintage Cessnas have the stall horn protected by an automatically resetting circuit breaker. So, for the mechnics in the crowd, does changing the stall horn to a pilot resettable circuit breaker comply with the type design....ie, is it legal? …

AC 43.13-1B Paragraph 11-50 (b) “Automatic reset circuit breakers, that automatically reset themselves periodically, are not recommended as circuit protection devices for aircraft.” I documented the swap to a pilot resettable CB as a minor alteration on my C-170B.