J model engine ground

[mooneyflyfast]

My engine ground strap runs from the prop governor (best I can tell without removing the lower cowl) to the firewall. is this typical?  I am having some intermittent charging issues and want to be sure the ground is good.

[Bartman]

I had an intermittent charging issue and found a bad terminal on the field wire connection to the alternator.  I looked at it and looks to me like that bundle of wires going to the back of the alternator is susceptible to vibration resulting in failure of the wire where it was crimped onto the connector.  
 

I think my ground strap is connected as you described. 

[mike_elliott]

J's and F's  field wire tend to break right at the alternator and should be a regular inspection at oil changes IMO. 

[Ragsf15e]

2 hours ago, mooneyflyfast said:

My engine ground strap runs from the prop governor (best I can tell without removing the lower cowl) to the firewall. is this typical?  I am having some intermittent charging issues and want to be sure the ground is good.

That’s how mine was connected as well.

Time to use a digital volt meter on the VR and field wiring.

[Guest]

10 hours ago, mooneyflyfast said:

My engine ground strap runs from the prop governor (best I can tell without removing the lower cowl) to the firewall. is this typical?  I am having some intermittent charging issues and want to be sure the ground is good.

That is the correct location for the ground cable.  When I install an engine I often install a second ground cable on the left side.

Loose field wire connections, followed by worn brushes would be places to look.

Clarence

[A64Pilot]

What about the field connections on the back of the Master switch? They are real easy to clean / diagnose, just wiggle the wires when it’s acting up and see if it stops

Edited May 14, 2021 by A64Pilot

[mike_elliott]

1 hour ago, A64Pilot said:

What about the field connections on the back of the Master switch? They are real easy to clean / diagnose, just wiggle the wires when it’s acting up and see if it stops

These connections will typically show the ammeter waiving like an old vacuum windshield washer for those of us old enough to remember them. Simply clean the connections on the MS really well and this effect will stop.

[GeeBee]

8 hours ago, mike_elliott said:

These connections will typically show the ammeter waiving like an old vacuum windshield washer for those of us old enough to remember them. Simply clean the connections on the MS really well and this effect will stop.

Wow, that does bring back memories!

 

[Guest]

10 hours ago, mike_elliott said:

These connections will typically show the ammeter waiving like an old vacuum windshield washer for those of us old enough to remember them. Simply clean the connections on the MS really well and this effect will stop.

The Mooney Mite uses a vacuum wiper motor as a gear warning device.

Clarence

[mike_elliott]

53 minutes ago, M20Doc said:

The Mooney Mite uses a vacuum wiper motor as a gear warning device.

Clarence

effectively, so does a vintage J bar Mooney with a worn down block

[PT20J]

18 hours ago, M20Doc said:

That is the correct location for the ground cable.  When I install an engine I often install a second ground cable on the left side.

Loose field wire connections, followed by worn brushes would be places to look.

Clarence

Really? From the prop governor? I don't doubt you, but it seems weird. I don't remember how it was on my 1978 M20J. I recall on my 1994 M20J (because we replaced the engine) that there are two heavy braded straps, one on each side, from a sump attach bolt to the firewall.

Skip

[A64Pilot]

A friend in High School had a Deuce Coupe with a Pontiac 389 tri-power in it, Any time you goosed it the vacuum windshield wipers would completely stop. but let off the throttle and they went to light speed

[A64Pilot]

39 minutes ago, PT20J said:

Really? From the prop governor? I don't doubt you, but it seems weird. I don't remember how it was on my 1978 M20J. I recall on my 1994 M20J (because we replaced the engine) that there are two heavy braded straps, one on each side, from a sump attach bolt to the firewall.

Skip

I’m going to look myself, because I’d rather not have any significant current flow through my prop governor, i know it shouldn’t, but I think it could. Too many other good places to ground an engine 

 

[David Lloyd]

There are a couple holes in the rear flange of the crankcase, one on either side, for the purpose of attaching a ground strap.  You could use the sump bolts or studs for the prop gov or a lot of other places, but Lycoming provided holes for you to use.  Just to the right of the gov pad, above the tube fitting.  And yes, I replaced the aluminum 45 degree fitting with a steel fitting.  This is a narrow deck 360, I assume the wide deck engines are similar.

[Guest]

4 hours ago, PT20J said:

Really? From the prop governor? I don't doubt you, but it seems weird. I don't remember how it was on my 1978 M20J. I recall on my 1994 M20J (because we replaced the engine) that there are two heavy braded straps, one on each side, from a sump attach bolt to the firewall.

Skip

Not directly to the governor, but usually to the bottom right mounting stud.  I looked in the manual under engine removal/installation, it mentions one ground strap but does not say where.  

Clarence