M20J Electric Clock ground wire

[allenawilson]

My 1980 M20J electric clock wasn't working and after being removed and bench tested at annual, it was labeled inop.  The OCD part of me doesn't like non-working stuff, so I took it out and had it repaired.  (Free, btw.  The points needed filing.)  When I removed it, neither wire was connected.  The positive wire was easy to identify, but I can't for the life of me find where to ground it!!!  HELP PLEASE!  Thanks, Allen.

[KSMooniac]

You can ground it to the back of the instrument panel...that's where the engine instruments ground.

Sent from my LG-US996 using Tapatalk

[carusoam]

+1 grounding to the IP...

Plus, check that the instrument panel has a good ground wire running to the fuselage... 

Sometimes grounds get old and then lost...

Best regards,

-a-

[allenawilson]

Thanks!  I'll report on results.  

 

[PT20J]

18 hours ago, KSMooniac said:

You can ground it to the back of the instrument panel...that's where the engine instruments ground.

Sent from my LG-US996 using Tapatalk
 

Well, actually, I don't think this is the best way to do it. The instrument panel is mounted on rubber LORD mounts for vibration isolation. There should be a ground strap to connect the panel to the frame for continuity, but Mooney doesn't use the panel for primary ground. The best way is to connect it according to the schematic in the Service Manual. But failing that, I'd connect it to a good ground on the tubular structure somewhere. Be sure to use aircraft-approved wire.

The clock is required equipment for IFR (91.205).

Skip

[allenawilson]

Update:  Found a good ground, but the hot wire is NOT hot.  Oh well...

[RLCarter]

9 minutes ago, allenawilson said:

Update:  Found a good ground, but the hot wire is NOT hot.  Oh well...

Now to find a good Hot . Chance are if you trace it out the hot has been "cut dead" at the circuit breaker

[Bob Weber]

16 hours ago, allenawilson said:

Update:  Found a good ground, but the hot wire is NOT hot.  Oh well...

I can't recall mooneys, but others have an old school fuse holder close to the battery just for the clock.

[Steve W]

10 hours ago, Bob Weber said:

I can't recall mooneys, but others have an old school fuse holder close to the battery just for the clock.

A late model Wiring Diagram(my plane 1994) shows the clock fuse in the vicinity of the battery/master relay in the tail.

 

[ltdoyle]

I had a similar problem on my 77.  Does your dome light work?  The dome light and electric clock are on the same circuit. It is fused with an in line fuse near the battery.  Mine had blown.

Edited September 28, 2019 by ltdoyle
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[PTK]

On 8/28/2019 at 11:48 AM, allenawilson said:

Update:  Found a good ground, but the hot wire is NOT hot.  Oh well...

There is a wire with its own inline fuse that powers the clock and oh lights. Look for it back around the relay on the battery.  Need to check that fuse and change it. It should be 5 amp slow blow fuse iirc. Also check to be sure the power wire at the clock is not shorting out by touching something. Mine was totally unshielded. When I changed the clock I wrapped with some shield and tie wrapped it. 

[jkarch]

On 8/26/2019 at 4:16 PM, allenawilson said:

My 1980 M20J electric clock wasn't working and after being removed and bench tested at annual, it was labeled inop.  The OCD part of me doesn't like non-working stuff, so I took it out and had it repaired.  (Free, btw.  The points needed filing.)  When I removed it, neither wire was connected.  The positive wire was easy to identify, but I can't for the life of me find where to ground it!!!  HELP PLEASE!  Thanks, Allen.

Wire a PIDG (terminal lug) from the clock to any screw post on the instrument panel  frame and you’re done!

Edited September 29, 2019 by jkarch

[jkarch]

These are PIDG terminal lugs