Changing from a Mando Alternator to a single-wire Alternator: Wiring problems

[Corto]

Hello,

I'm doing a lot of work on my 1991 Bayliner Capri with a 5.0L Mercruiser V8 and I am overhauling most of the electrics.
I've just fitted a new high-output single wire alternator to replace the old one (Mando-type I think) and I don't know what to do with the purple and red/purple excitation wires.

The earth and orange wire to the starter motor have been wired correctly and the motor was starting and running OK this weekend but I think that the alternator wasn't charging because:
a) I was getting no more than 12.5V at the battery when running the engine
b) There is no increase in voltage after starting the engine, and when revving the engine.

I connected the purple and red/purple wires back to a +ve terminal but that made no change to the voltage in the system.

Should I leave them isolated or connect them back to a +ve?
Is my alternator definitely not charging?

(BTW, I noticed that the alternator belt could do with some tightening but that shouldn't be the issue as the alternator is turning with the engine.)


thanks for your help

 

[Chris1956]

Re: Changing from a Mando Alternator to a single-wire Alternator: Wiring problems

I recommend you repost this in the I/O forum....

 

[Corto]

Re: Changing from a Mando Alternator to a single-wire Alternator: Wiring problems

thanks, will do so.