[stackj]

I am having a gear horn problem too. When I turn on the master switch, if the throttles are in the fully retarded position the gear horn will sound for a few seconds and then function normally. After I clean out my pants, I will engage the starter (either one) and the horn will sound again briefly... with each start. The green Gear Down light is on steadily during this process.

I did some voltage checks on the Dual horn assembly. There are 5 screw terminals on the module. I noted the following results with the Master switch on:

Green Gear Down light on.
Gear Horn sounding
With a voltmeter - Negative lead to airframe -

Measurements on screw terminals

Ground terminal - 0 volts (V)
Gear Terminal - 24 V
Power Terminal (center) - 24 V
Stall Horn Terminal - 24 V (stall horn was silent)
Throttle terminal (Throttles fully retarded) 0 V

Then, a little surprise. My airplane has a module part number 1213242-1 installed. It is clearly labeled as a 12 volt unit. The parts list calls for a 1213242-2 unit. When I do research on the Internet, that part number is listed as a 24 volt unit. Interestingly enough, the unit in my airplane has functioned perfectly for the 18 years I have owned the airplane.

When I read the operational description in the aircraft maintenance manual, I find that when the test button is pressed, the gear horn should sound while the switch is about half-way engaged and the light should be on when fully pressed. My inpression is that when voltage is applied to the Gear terminal of the gear warning unit, the horn should be silent. If this is the case, the indications are that my Gear horn module has failed - not the wiring or switching for the gear warning circuit.

Can anyone confirm if my logic is correct? I really hate to spend $1800 for a new unit that I don't need.

Does anyone have a diagram of the dual horn module? It may be able to determine the validity of my troubleshooting.