Rotax internal alternator warning light

Does anyone know if you need a lamp for field excitation for the built in Rotax 912 alternator? Or can I just use an led? There are some much neater solutions if I use an led panel mount and available from Jaycar avionics

Does anyone know if you need a lamp for field excitation for the built in Rotax 912 alternator? Or can I just use an led? There are some much neater solutions if I use an led panel mount and available from Jaycar avionics

I use an led. It works fine. I chose a yellow one because generally yellow is for a "caution".

I should also have mentioned that Ashdown Ingram have a nice selection of switches and lights including leds.

Also as you probably already know, polarity is important if using leds

Hi Danny from notes I have.

The Rotax 912 wiring diagram shows a “charge indicating lamp,” connected between terminals L and C on the rectifier-regulator. There is a lot of confusion about when this light should be on or off and exactly what it indicates. It is a warning light and should be red. The light should come on only when the system is not charging or is discharging the battery. If all is working well, you will see the light is on when you turn on your master switch, and it will go out as soon as the engine is started and the charging system begins to work. Rotax specifies a 3-watt/12-volt light. If you are installing a voltmeter and you don’t want to install a warning light, simply disregard terminal L on the rectifier-regulator

My edit time expired please add to previous comment reply.

I have a volt meter and watch for the 13.6, 13.8 after start up to verify the charging system to operating. (Its part of a GT50 gauge.)

I may have mentioned before; I am a very big believer (life experiences) in a warning light that the starter circuit is open after start. (you will see it in my panel images) I have an amber light that if it was to stay illuminated after start then I would shutdown and check out as the solenoid would have failed and stayed on for some reason; there a couple of reasons, this would lead to battery drained of voltage and the starter would be damaged if allowed the remain connected tom the voltage source. Only occurs rarely but you never want this sort of inconvenience or cost of repair - new battery and starter for rotax. (PS I'm not a worrier just a practical experienced repairer and operator of a variety of things in the 12 and 24 volt area.) Cheers and disregard anything you choose.

Hi Danny from notes I have.

 

The Rotax 912 wiring diagram shows a “charge indicating lamp,” connected between terminals L and C on the rectifier-regulator. There is a lot of confusion about when this light should be on or off and exactly what it indicates. It is a warning light and should be red. The light should come on only when the system is not charging or is discharging the battery. If all is working well, you will see the light is on when you turn on your master switch, and it will go out as soon as the engine is started and the charging system begins to work. Rotax specifies a 3-watt/12-volt light. If you are installing a voltmeter and you don’t want to install a warning light, simply disregard terminal L on the rectifier-regulator

Thanks.

What I want to specifically know is whether it needs 3 watts or not. Traditional alternator design meant you needed the warning light to allow a small current flow in the rotor winding to 'kick start' the charging system- a small magnetic field is created with that little current flow and then it cascades from there. On a traditional alternator, an LED wouldn't give enough current flow for the alternator to kickstart. I haven't been in the auto elec game for years so I'm not sure if that's still required. Also, if the Rotax built in alternator is like a small motorbike etc alternator then the rotor is magnetic to start with (no windings) and thus doesn't even need a light to start charging. M61A1 has said that an LED works for him so I'll go with an LED. As well as you mentioned from your notes, you can disregard the warning light altogether so that tells me it's not critical. I have a voltmeter as well but the warning light will give an immediate indication.

Regards the confusion about the warning light, it does seem strange to me. What do people think the warning light does in their car :D

Rotax 912 internal alternator has permanent magnets so no excitation is required.

Rotax 912 internal alternator has permanent magnets so no excitation is required.

Cool, I'm off to Jaycar avionics ?

Narva make flush mounted LED warning light which is what I used to replace the failed alt light in my Foxbat. $8 from local auto store. Part Number 62076BL

Narva make flush mounted LED warning light which is what I used to replace the failed alt light in my Foxbat. $8 from local auto store. Part Number 62076BL

That was the one I was going for. Really neat. But in the end I decided to go with something else.

So another question. I'm finding it hard to see how the warning light is wired for the rotax. I see some places say between C and L on the rectifier? Is that right?

So another question. I'm finding it hard to see how the warning light is wired for the rotax. I see some places say between C and L on the rectifier? Is that right?

That is correct.