If I had to venture a guess here I would say you are measuring both
batteries in series somehow and one is 12+ - volts and the "coach battery"
is 10 volts + -  ( Bad )  and is why your accessory's are not working.
jeff

On Tue, Jun 16, 2009 at 3:14 PM, Don Hanson <dhanson928@gmail.com> wrote:

>  From a dummy...
>
>  The last few months my coach battery hasn't seemed to be staying charged
> up as well as in the past. I've changed nothing recently.
>  So I got out my handy dandy Radio Shack digital meter today and began
> poking around.  I find lots of Volts.  Dunno what it should be, but I seem
> to have too many at the Vehicle battery and plenty at the Coach
> battery..however, my water pump is kinda slow and the Westie Indicator
> lights are on the Red bulb most of the time (when the  engine is not
> running)..
>  My system:
>  I have two identical NAPA batts. of around the same vintage (aug '07)
> These are "sure start  65"  BCI 42 with 500cca and 250amps.  One under the
> passenger seat (the vehicle batt) and the Coach batt under the driver's
> seat.  I have a big wire (fused, of course) across (vehicle to coach batt)
> which feeds a big 'mechanical' can 3 terminal relay, also under the drivers
> seat.  This relay is controlled by a wire from the ignition and the wire is
> also switched (that supply wire from the ignition to the relay)...I wasn't
> sure about starting the vanand how the two batteries would inter react
> during start up, so I began by having that secondary switch off whenever I
> started up...That proved to be un-necessary but it is nice to be able to
> cut
> the power to the secondary battery without shutting off the van..
>  Ok, so I run the van and check the relay...Flip the switch from the
> ignition to excite the relay and "Click!" it works fine..
>  But the numbers (from my digital meter) don't make sense....Oh yeah, when
> the van is running, the Westie stove-front power indicator light goes
> Green...engine off..Red...on Green.
>  From my digital meter:  Vehicle battery..Van off reads 20.6  Van running
> reads 21.8
>                                     Coach battery...Van off reads 17.3  Van
> running and relay active reads 21.7
> I double checked with an older analog meter and my Radio Shack one is
> functioning fine...though I wasn't sure which scale to read on the analog
> meter, it is consistent with the digital one.
>  So how come so many volts?  Is this bad?  Or is my meter simply screwy or
> my testing technique faulty?
> Also, across my 'mechanical' relay (a silver cylinder with two (+/_) large
> terminals and a 'supply' terminal..I am seeing (I think) some current when
> there shouldn't be any.  I see about 4 volts across the two main (+ (in
> from
> the vehicle battery) and -(out to the accessories in the coach))
> connections.  That shouldn't be, unless perhaps the relay is now faulty?
> Anybody care to take a shot at this weirdness?
>  I am thinking I probably have a couple of things going on here..Maybe my
> meter is reading wrong and maybe the relay is faulty.
>
>  The setup has worked pretty well for me for about 18 months including a
> prolonged (4 months) outing where the Van was used as a second bedroom and
> work/play vehicle daily..I would get about 2.5 hrs of satellite radio,
> incandescent light and some computer time before my coach battery went
> down...At present, I'd guess maybe I'd be getting about 1/4 that, so
> something is out of whack somewhere...I know I could have a more
> appropriate
> electrical system but I don't want to re-do the whole thing right now.
>
>  Don Hanson
>

--
Jeff Ensing
Ensing Remodeling
3327 hidden acres Drive
Atlanta, Ga. 30340
678-549-8430