Re: Bad alternators or am I frying them?

Posted by John T on November 04, 2022 at 08:58:20 from (45.16.200.171):

In Reply to: Bad alternators or am I frying them? posted by BarnyardEngineering on November 04, 2022 at 07:30:27:

Mornin Barnyard, here's my thoughts:

1) On the old VR its BAT terminal is what got to the battery to charge it, often via a series ammeter so
the wire that used to attach to BAT on the VR should wire to the alternators big main output stud HOWEVER
I usually upgrade that wire to at least 10 Gauge.

2) Its ONLY 4 terminal VR's (BAT ARM FLD LOAD) that have the 4th extra LOAD terminal which feeds loads
like lights and ignition......On 3 terminal VR's (BAT ARM FLD) those loads are instead fed from the Load
(NOT battery supply) side of the ammeter.

3) The LOAD on 4 terminal VR's (while sure it feeds battery voltage) is NOT quite the same as the BAT
terminal. The LOAD is used so the genny can feed loads voltage without them passing through relay contacts
and in theory its supposed to provide better regulation.

4) Even if it works I would NOT use the old VR like a buss bar but instead transfer loads like lights and
ignition up to the LOAD (NOT battery supply) side of the ammeter.

THAT BEING SAID I still cant say for sure or know if that matters and is whats hurting your alternators.
On the Delco 10SI family the small 2F terminal (1R is excitation) is for voltage sensing and many people
just jump wire it down to the big main output stud and that works HOWEVER if wired instead to the battery
thats a better location as far as battery voltage but Ive never had problems using 2F to the output..

While incorrect voltage sensing (location or how its wire and if right) can harm an alternator (sees low
voltage so it cranks up) I dont know how if and where your 10SI is wired so dont know your problem

DISCLAIMER Im more into genny and VR systems and electrical power than electronics so see what the more
electronic minded gents here have to say as Im NOT any alternator expert. The ONLY things I have to offer
is insure the alternators 2F is wired correct to sense voltage (may harm alternator otherwise), you did
swap to NEG ground I trust, and dont use the VR as a buss bar, wire loads to ammeter instead

John T

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