diodes for lighting

Can I use an LED as a diode?
No, because you would have to connect both (potential) positives to the same leg of the LED. Switch one on and you make the other live. I'm sure you realised that 5mins after posting, which is what I usually do.:)

Yes you could use 2x LED in stead of 2x 1N4001 or similar. However LEDs have a limited current capabilty so it depends on what kind of light bulb you have in the compass.
If you have an LED bulb in the compass then OK however the LED used as a diode will drop about 3v so assuming the compass LED has a current limiting resistor attached to it the compass light will be dimmer than direct connection. (needs a lower resistance for correct brightness) If it is an incandescent bulb the current drain of the compass bulb will probably melt the LED used as a diode through too much current.
No point in using an LED unless you want indication at the switch board as the LED used as a diode should glow OK. NB here we are talking actual LED diode not one of those LED +resistor lights for 12v operation. Just being pedantic olewill
 
No point in using an LED unless you want indication at the switch board as the LED used as a diode should glow OK...
In this case it would be better to add a separate LED and dropper resistor, due to the current capacity and voltage drop as you mentioned. My offer in #13 to make up a Y lead still stands, just need to know the fuse rating of the existing switched feeds.
 
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With my mighty MD1 (not MD1B ) thumping away beneath my feet, I don't think I'll need an indicator light! I am < 7m so don't need a tricolour and don't want to run my red/green/white when not charging the battery.
That would suggest that you are sailing with your anchor down!

Here's a thought, replace compass light with two LED's, one red for motoring and one blue for sailing, then at a glance of the compass you will know if you are motoring or sailing :) :devilish:
 
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