Volvo 2020 Alternator damage?

[StugeronSteve]

How long does the power on/off switch need to be off (with the engine running) to damage the alternator diodes? And if any such damage occurred how would it manifest itself?

Swmbo inadvertantly caught the alarm test switch and, hearing the beep, thought that she had switched off the ignition and immediately switched it back on (actually off). It was only off for about five minutes before I noticed the fuel gauge and rectified the matter. Is there likely to have been any harm done?

I didn't have a multitester with me, but when we got back to our berth I put a heavy load on the batteries by running all the 12v items and could see from our crude -three lights voltage meter- that the engine was charging, 12v showing with engine off, 13v light flickering at tick over and >13v as soon as the engine revs were increased.

 

[Chris_Robb]

Hi - turning the battery switch off is the killer. Just turning the ignition off should have no effect. I presume from your description that the Memsahib turned the ignition off, rather than the battery. Sounds like you have a working alternator, otherwsie you would get no voltage rise. Just as well with a sunny bank holiday forecast - fridge will need to be running for the beers!

 

[alldownwind]

I agree, sounds like you've got no problem at all there.

 

[StugeronSteve]

Cheers guys, just as I suspected. Yep, it was just the on/off push button that she caught.

 

[VicS]

As Chris Robb says switching off the "ignition switch" will not have caused any problems. It is disconnecting the battery, eg by opening the battery isolator switch, while the engine is running that will destroy the diodes in the alternator. That will occur instantaneously, no time delay.
Switching off the "ignition switch" will have disabled the engine instrumentation and warnings while it was off that's all. If it had been a petrol engine it would have stopped the engine! You'd have noticed that sooner!
Your simple indicator is telling your all is well but for peace of mind check the volts with a voltmeter and you should see a the reading rise to around 14volts as the battery charges fully. The actual reading will depend on the regulator you have.

 

[SvenglishTommy]

I have a faulty electronic unit in the switch panel for my 2010, so I regularly run the engine for hours with the ignition off. No problem at all.