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| combiner- isolator question- [message #166651] |
Tue, 17 April 2012 17:14  |
chasingsummer
Messages: 434
Registered: May 2011
Location: asheboro, nc
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i remember my isolator went bad last year, so i put both battery luggs on the same good terminal.
now as i consider proper repair i am leaning towards just installing a combiner and ignoring the fact that one of the diodes are bad,
are there any negative affects to connecting a combiner to a bad isolator?
also, since i see post related to the lights on the combiner, do i need to mount on dash so that as i constantly look at my stock gauges i have another one to stare at, or is it more of a mount up front somewhere and just forget about.
thanks
bgk
brian
asheboro, nc
75 eleganza, 74 build
119k miles and counting,
DOG HOUSE
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| Re: [GMCnet] combiner- isolator question- [message #166658 is a reply to message #166651] |
Tue, 17 April 2012 18:01  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Brian,
You CAN use the bad isolator as a convenient location to attach the
combiner. Just return the moved wires back to where they came from (one
battery to each outer bolt). Then attach the two primary (red) wires of
the combiner to those outer bolts.
There's no reason to mount the combiner on the dash. The lights are not of
much interest except for troubleshooting, IMHO. If you REALLY like having
things to watch, there's a lead on the combiner which can be used to attach
one -- I've never bothered.
Ken H.
On Tue, Apr 17, 2012 at 6:14 PM, brian wrote:
>
>
> i remember my isolator went bad last year, so i put both battery luggs on
> the same good terminal.
> now as i consider proper repair i am leaning towards just installing a
> combiner and ignoring the fact that one of the diodes are bad,
> are there any negative affects to connecting a combiner to a bad isolator?
> also, since i see post related to the lights on the combiner, do i need to
> mount on dash so that as i constantly look at my stock gauges i have
> another one to stare at, or is it more of a mount up front somewhere and
> just forget about.
> thanks
> bgk
> --
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76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] combiner- isolator question- [message #166662 is a reply to message #166659] |
Tue, 17 April 2012 19:28 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
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That's right, but he specified that his corrective action was to bypass the
diode, which would not have been necessary if it was shorted.
Incidentally, I've yet to hear of an isolator diode failing shorted --
even though it SHOULD happen.
Ken H.
On Tue, Apr 17, 2012 at 7:30 PM, D C *Mac* Macdonald <k2gkk@hotmail.com>wrote:
> That's a good choice only if diode(s) fail open, right?
>
> Mac in OKC
> "Money Pit"
>
>
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76 X-Birchaven
76 X-Palm Beach
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| Re: combiner- isolator question- [message #166665 is a reply to message #166651] |
Tue, 17 April 2012 20:01 |
chasingsummer
Messages: 434
Registered: May 2011
Location: asheboro, nc
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diode to engine battery opened, no charging to engine battery, that was why temp fix, to charge engine battery. plan is to leave isolator in as a connection point,
if i understand diodes, they can short, but life resister, once they do current goes up which then burns them open.
and no, i did not really need anymore gauges to stare at, i already stare at mainly temp gauge enought , way too much.
trying to get ready for camping tri p next month.
brian
asheboro, nc
75 eleganza, 74 build
119k miles and counting,
DOG HOUSE
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| Re: [GMCnet] combiner- isolator question- [message #166669 is a reply to message #166662] |
Tue, 17 April 2012 20:58 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Ken Henderson wrote on Tue, 17 April 2012 20:28 |
That's right, but he specified that his corrective action was to bypass the
diode, which would not have been necessary if it was shorted.
Incidentally, I've yet to hear of an isolator diode failing shorted --
even though it SHOULD happen.
Ken H.
On Tue, Apr 17, 2012 at 7:30 PM, D C *Mac* Macdonald wrote:
That's a good choice only if diode(s) fail open, right?
Mac in OKC
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You don't work on other people's pleasure boats or you would have seen a few.
I have seen as many of these go solid (0.0 drop both ways) as I have seen go open.
No, I can't describe the conditions that cause each. The owners that cause this sort of thing can't usually explain what happened in such a way that makes any sense. I'm usually there to fix it and get the boat usable again.
As best I can build, if you run with a shorted cell and the ratings are close enough together, the diode can cook and go solid. If you hook a battery up backwards or short the cables, then the blow at least the diode and sometimes some epoxy - too. All of these also do other damage, so usually the isolator is just a distraction while getting alternators replaced and cleaning up acid spills.
Why I used to keep a spare isolator on the shelf.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] combiner- isolator question- [message #166673 is a reply to message #166669] |
Tue, 17 April 2012 21:30 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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You're right. GMCers must be more cautious than boat owners. :-)
Your results are what I'd have expected under the abuse described.
Considering only the actual diode itself, without any of the external
connections, a diode should never open except in the case of a gross
over-current condition, such as with the reversed battery, when the diode
becomes the fuse.
I started to bore everyone stiff with solid state physics, silicon doping,
PN junctions, etc., but there's really no excuse for all that political
stuff here. :-)
Ken H.
On Tue, Apr 17, 2012 at 9:58 PM, Matt Colie wrote:
> ...
>
> Incidentally, I've yet to hear of an isolator diode failing shorted --
> > even though it SHOULD happen.
> >
> > Ken H.
> >
> You don't work on other people's pleasure boats or you would have seen a
> few.
>
> I have seen as many of these go solid (0.0 drop both ways) as I have seen
> go open.
> ...
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76 X-Birchaven
76 X-Palm Beach
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| Re: combiner- isolator question- [message #166674 is a reply to message #166665] |
Tue, 17 April 2012 21:41 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
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| chasingsummer wrote on Tue, 17 April 2012 18:01 |
diode to engine battery opened, no charging to engine battery, that was why temp fix, to charge engine battery. plan is to leave isolator in as a connection point ...
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IF you plan on keeping the "bad" isolator, I would use the "good" side to connect the engine. Have the combiner add in the house battery as needed for charging. This would then maintain the "hot only with engine running" behavior of the alternator output line. (Useful for electric chokes, fuel pumps and the like.)
In any case you need to supply a feed back for the alternator, from the chassis battery, that does NOT pass through the combiner. If not you'll have over-voltage during the delay before the combiner kicks in.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] combiner- isolator question- [message #166677 is a reply to message #166674] |
Tue, 17 April 2012 22:20 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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EXCELLENT point, Mike, which I should have mentioned during my initial
reply. Without the feedback connected, the "runaway" alternator could
subject everything connected through the remaining diode to catastrophic
voltage, as well as over-stressing itself.
In fact, on second thought, I think anyone who does not need the isolated
alternator output (for the purposes you mentioned) should connect the
chassis battery AND the alternator to the center terminal. That way, the
feedback circuit will not be dependent on anything except solid
connections. The house battery, connected via the remaining diode, will
see 0.7 VDC low charge voltage, but only until the combiner closes.
Thanks for pointing out my oversight.
Ken H.
On Tue, Apr 17, 2012 at 10:41 PM, Mike Miller wrote:
>
>
> chasingsummer wrote on Tue, 17 April 2012 18:01
> > diode to engine battery opened, no charging to engine battery, that was
> why temp fix, to charge engine battery. plan is to leave isolator in as a
> connection point ...
>
>
> IF you plan on keeping the "bad" isolator, I would use the "good" side to
> connect the engine. Have the combiner add in the house battery as needed
> for charging. This would then maintain the "hot only with engine running"
> behavior of the alternator output line. (Useful for electric chokes, fuel
> pumps and the like.)
>
> In any case you need to supply a feed back for the alternator, from the
> chassis battery, that does NOT pass through the combiner. If not you'll
> have over-voltage during the delay before the combiner kicks in.
>
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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