Help with alternator and external Reg.

[WindBoatMan]

Hi there,

I've been using this excellent forum as a resource for a while and using the advice shared to help with my project. I have spent the last 2 years restoring a 1938 40ft teak hull river cruiser and am in the midst of the big rewire. I have attached a couple of pics of the project.

I'm pretty knowledgeable with the 12v side of things and have been re-wiring with a friend who's an auto-electrician checking over my work as I go along.

I have a bit of a dilemma with a prestolite alternator to solve and was wondering if anyone may be able to shed some light on this.

Here's a link to the literature on the alt -http://www.prestolite.co.uk/literature/alts/G770_8mr2049.pdf mine is the same but a 90amp model.

I want to connect this alt to a new external regulator, a PDAR unit made by Sterling Power. I know that this is a -ve field Alt and need to connect the external reg to the -ve field wire on the back of the alternator. I wanted to find out if I was going to be lucky and that one of the existing external connections shown in that PDF is a direct connection to the negative field brush? Otherwise, if not, I have to crack the existing regulator and solder a wire onto the negative field (the wire labelled as the excitation wire seems to be already connected to the brushes?!).

Many thanks in advance all.
Adam.

[jonr]

I'm curious - why not just use the internal regulator? My guess - you need to cut apart the internal regulator.

[gonzo]

There is a regulator terminal. It just occurred to me, is this a positive ground system? If so the wiring diagram is backwards, and the standard regulator won't work. Are you attempting to reverse the polarity?

[WindBoatMan]

Hi Gonzo,

Thanks for looking at this. Its a negative field rotor. The external regulator unit I would like to wire in is a very advanced regulator that makes the alternator work like a 4 stage digital battery charger, they're fantastic units and get much more charging capacity out the alt that standard alt regs (much like the Mastervolt Alpha Pro Regulator). It bypasses the regulator on the alternator and if for any reason stops working the old reg would kick in to back it up.

As stated in the 1st post, this external regulator needs a feed off the negative field brush and I was hoping that one of the existing connections on this alt is the feed I need?

Thanks. Adam.

[bertho]

Adam,
I do the same with 2 prestolite alternators ! sterling regulator is working well , but look fragile, burn 2 already...and one start to look strange , often trip due to a negative defect alarm ?? with all negative wiring ok
the connection is well explain on the manual, (also in Internet sterling site)
best rgds
Bertho
www.fusionschooner.blogspot.com