Dumb electrical question, alternator wiring

[Canuck Dennis]

Installing new 150 a aternator on dd 12v 71 n.

can see neg and pos connections, but, question on the exciter connection.

I assume it is excited via fuel pressure switch, therefore, run wire from pos terminal on alternator to press sw and line from other side of press sw back to exciter terminal ??

there is no ign sw on engine.

I am concerned because the pos terminal on the alternator is always hot, therefore one side of fuel press sw is hot, if fuel press sw failed close when engine shuts off, the alternator could try to energize and act as a motor ??

It appears the current wiring is like this but would like to confirm .

Thanks again.

UPDATE !!!! FYI

apparently the fuel press sitches may not be able to pass enough amps to keep the alternator excited due to high output style, suggestion is to use fuel sw to fire relay rated minimum 15 amps. Thats what the supplier suggested.w

[Boatsb]

Dennis some alternators only have 1wire. My new ones do Just a hot lead and the ground through the body. Check with the alternators manufacturer before you start modifying things

[krush]

Check the discussion in this thread. It will give an idea of what the wires do http://www.samsmarine.com/forums/showthread.php?t=10404

OEM setups are usually not single wire (self exciting). If there is no "ignition" that provides 12v power when you have everything on, then your solution sounds like a viable alternative. You will have that hot wire all the time the battery switches are on though.