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2G External alternator voltage regulator

turbosax2

Moderator
4,415
428
Nov 19, 2006
Mechanicsburg, Pennsylvania
Has anyone ever converted to an external alternator voltage regulator? I have a 200A Saturn alternator with stock 2g pulley, and get plenty of voltage at anything but idle (~14.7v), but at 750rpm idle it can get as low as 12.3v. I've been meaning to swap the smaller pulley on that came with the unit, but I've heard from others than it still doesn't make great voltage at idle. I'm not willing to raise the idle rpm, and I'd rather not swap to a stock Saturn alternator, so I'm considering using a universal external voltage regulator instead. Just wondering if anyone has any experience with these they could share.
 

estoyaqui30

Proven Member
581
22
May 26, 2003
Somerset, New_Jersey
I have not heard of it being done, but I asked the same question quite a while ago and got no response. The only thing that seems to fail on our alternators is the regulator. I'm sure that is from the heat of the exhaust and turbo. I was thinking that a remoted, external regulator could be placed away from the heat, maybe even near the fuse box.

Just my .02
 

silvreclips

15+ Year Contributor
1,283
348
Jul 19, 2005
Greenville, South_Carolina
The 4g63 alternator looks very similar to the 420a alternator. For those of us that dont run a stock ECU anymore we use an external voltage reg from a dodge omni. I had similar issue as you did, low voltage at idle and it was even worse with the lights on and fans running. Once I changed to the external reg I had a much more stable voltage.

This is what I am using. You can buy them at Orielys auto parts for about half the price and they have the pigtail for ab 12 IIRC. I think its from an 88 omni

420A/Neon Alternator Voltage Regulator - SymTech Laboratories

http://www.symtechlabs.com/support/docs/VregInstall.pdf
 

turbosax2

Moderator
4,415
428
Nov 19, 2006
Mechanicsburg, Pennsylvania
Thanks for the link. Are 420a alternators internal or external regulators from the factory? I was under the impression the regulator for them was in the ECU, meaning that you'd just be swapping from one external regulator to another.
 

silvreclips

15+ Year Contributor
1,283
348
Jul 19, 2005
Greenville, South_Carolina
Yes the ECU controls the regulator. Judging from the plug on the back of the 4g63 alternator I was assuming that those are controlled the same way.
 

turbosax2

Moderator
4,415
428
Nov 19, 2006
Mechanicsburg, Pennsylvania
Well, the ecu has some control over the alternator in factory form, but there is an internal voltage regulator inside the alternator itself that would need modified to switch to an external regulator.
 

silvreclips

15+ Year Contributor
1,283
348
Jul 19, 2005
Greenville, South_Carolina
This might help you out some.

http://simon.chi.il.us/ECU/2gAlt.jpg

L energises the field coil
S is the sense line for regulation
B is the output

G is the control line to the alternator
FR is the status from the alternator

The first three are shared with the 1G alternator.

*Found on dsmtalk*
 
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