That cheap load tester is a handy device. I have a similar
one that is now probably twenty years old, but continues to be helpful with
battery diagnostics. The new ones are much more expensive, but include
microprocessors and can supposedly diagnose battery faults that primitive load
testers with resistive element cannot.
Battery selector switches used primarily in the marine market, but
also in some RVs, have positions labeled “bank 1”, “bank
2” and “both” are designed with a ‘wiper’ contact
that “makes before break”. In other words, the contactor
(wired to load as well as alternator) actually makes contact with the next
position, before relinquishing or opening contact with the previous position.
This insures that the alternator is not accidentally operated into an open
load.
I don’t think that a battery charger up against the output
side of an alternator would cause an issue as these diodes should be able to
easily handle. It’s a thought perhaps when considering that some
inverter/chargers are capable of charging currents in excess of 100 amps dc.
There is a tremendous amount of decent easily understood electrical
info available on http://bluesea.com.
The hardware Blue Sea designs/distributes is well built, reasonably priced and
most likely an upgrade from what we find in our Wanderlodge electrical system, possibly
a weak link in our otherwise ‘bullet proof’ RVs.
Donn
76 FC33
South Kingstown, RI
I dont know, may be that is where they are failing more often in motorhomes, by
being run with the battery bank turned off? or up against a battery bank being
charged via a shore wire at a higher than 13 amp? If the rectifying diodes are
that burnt it would suggest your claim. I have a battery/alt test device that
make a heat coil load I think it was about $30. from harbor freight not a very
good instrument but one more test to help make a decision. I was unaware that
running an alt without a load would cause harm to the alt
Greg of Tim&Greg
94ptca
--- In "WanderlodgeForum%40yahoogroups.com",
"Donald Watson" wrote:
>
> I appreciate your posts Greg, especially since you have a pretty
diversified
> experience with heavy equipment.
>
> That being said, did you really mean, "Check the output when output
wire is
> disconnected from bus batteries." ??
>
> Without a battery or batteries to act as a load, I believe the rectifying
> diodes would burn up in an instant. Greg's suggestion of lifting the
> alternator output cable on both ends , checking continuity as well as
> resistance to ground is a reasonable one. I have a friend who drives over
> the road with a 60 series Detroit. He goes through alternators quicker
than
> he should and I wonder if it is simply the quality of the rebuilds that is
> questionable as Greg suggested.
>
> Donn
> '76 FC33
> South Kingstown, RI
>
> From: "WanderlodgeForum%40yahoogroups.com"
> [mailto:"WanderlodgeForum%40yahoogroups.com"]
On Behalf Of gregory O
> Sent: Tuesday, October 13, 2009 9:12 PM
> To: "WanderlodgeForum%40yahoogroups.com"
> Subject: [WanderlodgeForum] Re: Front Alternator 8V92
>
> alternators require many working parts any one part that fails will not
> allow it to work. when a bearing goes out it still pumps amps but the heat
> can screw the windings and vr. if the prior rebuild didnt repair the
bearing
> or other cause for resulting failure replacing a burnt electrical
component
> will be short lived, like in your case. The other possibility is something
> is burning out the electronics and replacing the alt will only prove that
> point with a third failure.
>
> Check the output when output wire is disconnected from bus batteries. I
> would then take the alt to a good rebuilder.
>
> one other test is to remove both ends of the charge wire, insulate the
> battery end, then check for continuity with ground at the alt end. there
> should be no continuity, if there is, 'continuous path' will show a ground
> fault which will always demand amps.
>
> You can usually find a referral of a local parts re builder from a local
> salvage yard. WHen ever I am forced to buy a Pepboys reman alt or starter
I
> drop it off at my favorite rebuilder in Riverside Ca. they ship
> http://riversidealternatorstarterac.com/
> Greg of Tim&Greg
> 94ptca
>
> --- In "WanderlodgeForum%40yahoogroups.com"
> , "SteveQ"
wrote:
> >
> > I had the front alternator rebuilt in 2007 right after buying the
coach,
> and have about 25,000 miles +/- since then. After testing it today it is
> dead again, there must be an underlying problem. Any ideas?
> >
> > Steve Quandt
> > 1993 PT40
> > Iron Mountain, MI
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