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Old 06-08-2010, 07:47 AM   #1
timjet
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Join Date: Apr 2009
Posts: 1,920
Engine alarm install

I just installed a Borel raw water alarm in my twin engine ACMY. The instructions say to supply 12v DC power from a source that is switched on when the engine is on. I connected the supply voltage to the unit from the key on hot side of the ignition switch on the bridge of the port engine, ie power to alarm when the key is in the on position. Problem is if the port engine is shutdown for any reason, the starboard engine is unprotected unless I leave the port engine key switch in the on position. I could run an additional wire from the stbd key switch to the alarm the same as the port engine, but I don't think that would be a good idea, having a source of 12v to each engine key switch even with the engine shutdown. I guess installing a diode in the wire from each engine key switch would solve the problem, but wouldn't have a clue on how to do this. Of course I could supply power from anything that is on the bridge that receives power all the time, but I would rather have the alarm powered only when the engine(s) are running, ie engine switch is on. Any ideas??

And along a related matter, I have a fuel transfer pump that will allow transfering of fuel between the saddle tanks. Very convienent until you forget you're transfering fuel, so to preclude this I want to install a small red "reminder" light that illuminates anytime the pump is energized. Since this is a reversable pump controlled by a DPDT switch (I think) I don't think it's a good idea to supply power to the light through the switch. Again, any ideas??

Tim
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