Confused regarding GEN OFF Bus light on 737 electrical panel

[737Andi]

Hello,

I'm a little bit confused regarding the meaning of the 2 blue "Gen Off Bus" lights for the 2 Engine Transfer Busses of the 737-800.

This website http://www.b737.org.uk/electrics.htm says: "The engine and APU generator OFF BUS lights illuminate when the respective generator is running and of the correct quality."

And this site https://de.slideshare.net/theoryce/b737ng-electrical-power&ved=2ahUKEwjl states: "IDG is not supplying power to the related transfer bus."

From my understanding the blue light for the eng busses always lights up when the IDG is not supplying power to the busses. But that does not say anything about the Generator being running or not.

So the blue light can also light up with an IDG not running, which is contrary to the sentence from the first cited website.

Or am I fully misunderstanding this light indicaton?

Thanks!

[737Andi]

No one? 😞

[Capt Quentin McHale]

Andi,

The 2 blue lights mean exactly what they say....Gen Off Bus.

If we combine the wording from both websites and come up with this statement ....."The engine and APU generator OFF BUS lights illuminate when the respective generator is running and of the correct quality AND is not supplying power to its respective BUS", I'm pretty sure we are on the money.

The GEN OFF BUS will also illuminate if you carry out a engine GEN disconnect (even though the Generator is not mechanically running). Hope this helps.