Gear Horn Issue
 

I have an interesting scenario with my landing gear system. I am almost certain that it is something electrical.
When landing and there is a bump (typically on rough, grass strip or semi-hard landing) the gear horn starts blaring. If I push the green light it stops, if I move the throttles forward beyond the point that the micro switch changes it stops or if I cycle the gear handle down (while the engine is still running) after it cycles and the handle returns to neutral it stops. When the horn goes off, the green light is off.

Another scenario was, after landing and the horn sounds again, I had parked the plane and left it in that position, horn on, and green light off. I then wanted to open the gear doors and normal procedure is to use the hand pump to open the doors. As I went to close the doors, normal procedure is to turn on the master and then pump by hand. Well when I tried this I could not pump and I think it is because the valve did not switch when the master was turned on to change the fluid flow. I had to lower the gear handle and then I could pump by hand until the doors closed and the gear handle came back to neutral. When I started the plane to leave the horn was not on anymore because of the above exercise. I am thinking that I have a bad DOOR SOLNOID VALVE (see attachments). If this unit is failing could this be the scenario? Sure sounds like this is the culprit. Any thoughts?

beats the heck out of me, but you have to have your front engine running if you want to pop the gear handle down. It doesn't do anything with the front engine shut off. Also, I think it's an uplock issue, because the doors drop down.

oh, missed that

Larry
While tied down on the ramp, after I pumped the doors open I could not pump them back up (with the master on) without dropping the gear handle first and then pumping the doors up until the handle went to neutral. This was all done with the front engine off (rear engine too)

Check the main gear down lock switches. It is possible they make a very soft contact. I had a similar problem. I had to put a shim on the contact pads so the switch would make a very firm contact. I guess the contact pads wear with time. Additionally, you can replace the switch actuator arm (part number S2112-1) too, without replacing the switch. An actuator arm is only $12, but the whole switch is $100+. Let me know if this helped.

Herb;
I had this problem (but inconsistent) with the horn. Never tried the hand pump test, but I am not surprised because the light circuit is hooked into the horn circuit, (and into the door solenoid) as you know. I think the prior thread suggesting to look at the switches is a good place to start. I think the solenoid either works or it doesn't. When they were troubleshooting all my problems they tested it by simply putting power to it...if you get a nice solid click, all is find with the solenoid.

Bill

With my gear problem, it worked fine during the manual hand pump down. But in flight, with a dynamic load on it, the switch didn't make a full contact.

Gear Horn issues
 

With my '70 C337E. When the gear is up and throttles open horn sounds . Press to test the green light, light comes on horn quiet. When gear goes down, horn quiet, green light on.
Did anyone find a solution??

HEW

What about your throttle body switches on the engine? Are they adjusted correctly? They should sound the horn when the gear is up and the throttles are pulled back to low power. It is a warning system to alert you that the gear is not down. One on each engine

Throttles ok
 

Yup, throttle microswitches ok.

Intermittent faulty throttle microswitch
 

Got rid of the noise of the gear warning horn. One of the throttle body switches had an intermittent fault which didn't show up on ground testing but then did so in the air and occasionally went away. While waiting for a new microswitch we simply bypassed the microswitch allowing the other engine to provide the gear-up throttle closed warning. If we had just disconnected the ground from the warning noise box we would have lost all warning sounds. Nevertheless, I had trouble hearing the horn anyway as I have good noise cancelling headsets!