My Subaru alternator does a much better job than the original one. The
wipers are a little faster and the lights a little brighter.

Its also not going to smoke my ECU...

On Sat, Jun 12, 2010 at 6:05 PM, Alistair Bell <albell@shaw.ca> wrote:

> A few years ago I tried an aftermarket adjustable volt. reg. Looked
> just like stock but for the addition of a tiny pot. that you adjusted
> to get output you wanted. It worked fine for a while but then
> something went wrong with it and it stopped outputting.
>
> I had it adjusted to 14.2 or so, when alt warm but not hot. Output
> did go down a bit after alt. got hotter.
>
> I think the concept is good, I just may have got a bad one. I'd like
> to try it again, it was only around $39.
>
> I bet my post is in the archives, I'll have a look.
>
> alistair
>
>
>
> On 12-Jun-10, at 1:41 PM, David Beierl wrote:
>
> At 03:57 PM 6/12/2010, mark drillock wrote:
>
>> One question I have is how high can the regulator be fooled into
>> driving the output voltage of the alternator at the alternator? If
>> during charging the wiring connection between the regulator sense
>> point and the alternator output leg is somehow lost, what happens?
>> In gas Vanagons the loss of the connection to the battery is a very
>> real possibility and the ECU could still be on the alternator output
>> side, so if the regulator could force the output voltage very high
>> without knowing it I wonder if something bad might happen. In the
>> stock configuration the regulator sees the charging voltage at a
>> point internal to the alternator so a loss of the connection to
>> battery does not mean a loss of the sense connection as well. Any
>> data on this?
>>
>
> Excellent point.  Something bad could definitely happen.  On this
> unit and I presume all of them, if you float the input the alternator
> will go to full output which with a small load might be a very high
> voltage.  The sense input draws 8-9 ma at 14.5v, so to failsafe it
> would need a suitable resistor across where the internal bus was
> cut.  I'll figure out what suitable is, but it shouldn't be critical.
>
> Now if the sense lead is *grounded* that will definitely drive the
> thing to full output.
>
> I haven't addressed the situation yet of the alternator output no
> longer driving the battery, but the sense input still connected there
> -- effectively it's the same as floating the input, since it will be
> immediately carried down to the loaded battery voltage.  Looks like
> the systematic solution to that would be to get the 30 terminals of
> the ECU/Fuel relays off the direct alternator wire and feed them from
> up forward somewhere, either the fuse/relay panel 30 terminal or
> direct from the battery.
>
> Another solution would be to use a diode to bridge the cut instead of
> a resistor.  That way the internal regulator voltage should never go
> more than a diode drop above the regulator set point.  Not ideal,
> would want a warning probably; but not instant disaster either.  And
> put a quarter-amp fuse in the sense lead, so it would blow if the
> lead was grounded.
>
> Have I missed anything?
>
> Yours,
> David
>

--
Jake

1984 Vanagon GL 1.9 WBX 'The Grey Van'
1986 Westy Weekender/2.5 SOHC Suby 'Dixie'

Crescent Beach, BC

www.thebassspa.com
www.crescentbeachguitar.com
http://subyjake.googlepages.com/mydixiedarlin%27