Engine running, but oops, the key is off

[Mark]

I noticed last weekend that when I returned to the slip, my key had been turned of. It could have been that way for an hour probably. I have always understood that diodes and alternators however, can be very ornery. How much of a problem might I have and how do I know it. Yanmar 2GM20.Thanks

 

[Steve Dion]

heard the same thing

Mark:I was told the same thing. It CAN damage the diodes in the alternator. I have a friend that turned off the key all the time on his Yanmar and everything is still OK. I am not sure that this isn't a progressive type thing and it just weakes them. If it's working you can just check the output and see how shes doin'. If the o/p is up to spec, I would not worry about it.

 

[Henry Weber]

engine with key off

Are you sure that you are not confusing this with running the alternator with the BATT switch turned off? I believe the main idea is that there must be a load on the alternator to prevent the output voltage from exceeding the breakdown voltage of the diodes.Henry

 

[Gordon Torresen]

Key off

The key should definately be left on, not because of any damage to the alternator but because the key controls power to the "dash board". When it is off, you do not know if you have temperature, oil pressure or charging problems. Also, the alternator will not be recharging the battery.

 

[Doug]

Diode barbeque

Diodes don't deteriorate slowly when abused...they roast quickly. To prove this, try running your engine with battery switch to off instead of 1,2,on or all. It doesn't take long. In fact there is a product called "zap" or something like that (cheap) that is kind of a circut breaker for diodes, to protect them in the event this does happen. Doug