Charge light stays on

Bill, 

Thanks, a clear explanation.

What I've observed:

Engine off, light on, 13.4V

Engine on, light on, 13.8v.  I'm going to check that number tomorrow.  I'll check for other sources of light while I'm at it.

I first noticed light on, engine on while flying.  I was trying to say I cannot be 100% sure when the "engine on, light on" condition first happened and whether it was straight after putting the newly recharged battery back in the plane or later when I was flying.  I guess it doesn't matter, it's there now.

Steve

>>>Engine on, light on, 13.8v. <<<

Clearly the voltage increased into the battery charging range when the Alternator started spinning.

This indicates that the Alternator and Regulator are definetly working.

There is no reason that the light should be ON.

If the Regulator (L) side of the lamp is unintentionally being shorted to ground (Chaffing);  This would produce the symptoms you are seeing.

Closely trace the (L) wire from the Regulator to the Lamp.  Did it get pinched during the maintainance?

. . .

Disconnect the Regulator LAMP (L) wire.

If the lamp light continues to illuminate intermittently,  Suspect the Wiring, Not the electronics.

So yesterday I said....

"Engine on, light on, 13.8v.  I'm going to check that number tomorrow".

I checked - this is wrong (paralax while flying means I was mis-reading the voltmeter).

New observations:

engine off, 13.3 -13.5 volts, depending on load.  Light is on as expected.

engine on,  voltage DROPS to 13.0 - 13.2.  Light stays on.  RPM makes no difference. Light stays on (and it is definitely the light).

Any suggestions on next diagnostic tests?  I obviously need to check wiring, but beyond checking nothing has come loose and there is continuity, what are the next steps?

Any advice would be much appreciated - input so far has allowed me to know what to be looking for.

Steve

Now we're getting somewhere!

Engine OFF, Master Switch (and ALT Switch if you have one), ON

Measure voltage on regulator Connections R, B+, and C.  All should show Battery voltage.  ~13 relative to Ground.

You may have popped a hidden fuse.

Then measure from the Block to the metal case of the Regulator. Zero Is correct. Anything over 0.1 is a problem. 

If the propper voltage is present, Pull the connector Off the Regulator, inspect it abnormalities and reinstall.

- - -

May we assume you keep the battery on a Charger/Maintainer between Flights?

Hi Bill,

I got to the field tonight and took the panel off to access the Rectifier/Regulator.

"Measure voltage on regulator Connections R, B+, and C.  All should show Battery voltage.  ~13 relative to Ground."

They all do - 13.4v, the same as measured elsewhere in the system.

"Then measure from the Block to the metal case of the Regulator"

0 Ohms (I assume block = crankcase, sorry British english Vs US english)

While I was at it, I measured resistance across the stator at the regulator connections as advised by an engineer here.  Again 0 ohms.

I'm told the next test is measure current at the alternator connections to the regulator with the engine running to show the alternator is working and that I should get 30A.  If it does, the regulator has failed, but I'm also told that alternators are very unlikely to fail, the supplied Ducati regulators are known to fail quite commonly.  I'm not sure I want to be running the engine with the panel off, nor do I have equipment to measure 30A or know how to make the connections safely without pulling apart the wiring.  With the panel now off its easy to just replace the regulator and relatively cheap, so that's my plan.  If that doesn't work, I'll try something else.

Any thoughts or advice?

I don't use a battery charger/maintainer as a matter of course - it's not something I've seen a need for previously nor a common practice in the UK.

Steve