Likely cause of inoperative gear warning?

[RobertE]

I've got an M20J with a gear warning that stopped working. I'm sure there are many possible causes but is there someone out there who faced the same problem and can suggest where to look first?

[carusoam]

Gear warning horn, because...

Gear is up and the throttle out (micro switch in the detent), horn should sound...

Clean the switch and detent...

Not my area of expertise...

Best regards,

-a-

[larryb]

What stopped working? Light or sonalert?

[carusoam]

Larry,

Thanks, you were generous with my memory issue. I read "alarm" and answered "light".

We'll see if Robert has the same memory I have if he tells us about the bulb...

Best regards,

-a-

[RobertE]

I was referring to the tone. The truth is I've never noticed the light.

[Rustler]

Robert--

 

I had a similar problem with my '81J. It was sporadic at first, but then the horn just ceased operation. It turned out to be the switch that activates the horn when manifold pressure is reduced to a certain point without dropping the gear. The switch is on the back of the throttle cable, just aft of the panel. Replacing it returned the horn to service.

[larryb]

There are 2 lights I was thinking of, one in the annunciator panel, and the floor light that illuminates the mechanical indicator. The floor light is only on when the gear is down. In any case, you asked about the tone, and the most likely cause is the sonalert. It's a Mallory Sonalert 628P. They do go bad over time. There are two switches in the circuit, one that Rustler mentioned, and another tied to the gear position. Both have to be active for the alert to sound. I would start with the sonalert though, easiest and cheapest. Easy enough to figure out with a volt meter.

 

http://www.alliedelec.com/search/productdetail.aspx?SKU=70186622

[Epiphyte]

Let me know what you ended up doing to fix it. I have a similar problem, except mine was intermittent. It didn't end well for me.....I'm in the process of repairing the prop and underbelly.

[Epiphyte]

Oh yea, the engine too. how could I forget that part.

[Shadrach]

Ouch!

[N201MKTurbo]

It depends on what year J you have. They changed the warning system a lot back then. I had the same problem last annual and cleaning the micro switch on the throttle quadrant fixed it. I have a 77 J.

[RobertE]

Well, I've got to describe my problem as intermittant.  It's working again.  I bet N201MKTurbo is right - a dirty micro switch.  I've got a 1981 J.

[larryb]

Sonalerts will often go intermittent. I know this because my autopilot sonalert went bad last year. It sometimes beeped, sometimes not. Sometimes you could hear it faintly trying to beep. I asked my avionics shop about it and they confirmed this is common for sonalerts. Since your problem is intermittent, I would replace the sonalert first. A, it's cheap, and B, it's an easy 10 min job. I had 3 total, replaced them all.

[BillC]

Where is the sonalert on a M20J....?

[larryb]

There are two speaker grills in the roof between front and rear seats. Sonalerts are behind the right side grill. The real speaker is behind the left one. That's the way it is in my 84 j. 4 screws for the grill and 4 more for the bracket holding the Sonalerts.

[BillC]

Thanks Larry.