Gear/stall warning alarm

[Kim Geyer]

I may have one of the switches that Cessna provided with the service kit for that SB. I’ll see if I can find it in my stuff. They used epoxy instead of RTV. I’ll post a pic when I find it

[Kim Geyer]

I just listed the switch I had on eBay P/N 1570412-1
It’s got the epoxy

[n86121]

T

On top of the throttle for each engine is a little microswitch.

As I recall, the gear horn goes off if either throttle goes back near idle and ger NOT down.

I believe they both have to be closed.

Annoying little buggers.

Easy to check w cover off and a meter.

They are a common microswitch.

Aka 'digikey' common.

Any shop on any field should be easy to fix / adjust or replace

[B2C2]

The problem is that the circuit that looks at the microswitch has a pretty high resistance threshold, like 400 ohms or so to detect closure of the microswitch. Moisture on the switch body between the two contacts can cause the circuit to leak to ground and think the switch is closed. It doesn't help that the screws holding the switch to the throttle body are grounded and quite close to the terminals. Closed is the same as idle, so when you raise the gear with a leaky switch the horn goes off since it thinks you are at idle with gear up. You can test for this on the ground by advancing the throttles with the engines off and seeing if the horn test that you get by pressing the gear up indicator light stops buzzing once you advance the throttles. If it doesn't you have a leaky path in the circuit. I have this happen periodically. Usually flying for a bit dries out the switch and fixes the problem, but the RTV is a good idea. Ill try that.

[B2C2]

One other thing, once you pull the breaker that will shut off the noise, you cannot raise the gear. I'm sure its a safety feature Cessna put in there to prevent gear up landings if the breaker is pulled or popped. So if this happens you have to raise the gear, endure the noise for a few seconds then pull the breaker. On my last flight when this happened I did this, then about 1/2 hour later I reset the breaker and no noise as the switch had dried out.