Mike,
That tap is to allow you to drain the lines themselves. It SHOULD be at
the lowest point of that plumbing area.
Dropping back to your earlier questions about the level sensors in the
fresh water and holding tanks. I've been a little out of touch, so haven't
previously given you my experience with Coachmen level sensors/displays: I
think all Coachmen-built GMC's used the same basic system: Well nuts for
sensors with a gold panel bearing 2 meters for LPG level and Battery
Voltage, an Onan hours meter, an Onan Start/Stop switch, and illuminating
indicators for the level of a selected tank. My Birchaven was so equipped,
as has been every other Coachmen I've seen.
The electronics on the back side of the indicator panel is, naturally,
right out of the early '70's: Discrete transistors are plugging into
"turret sockets", and they're in the most fundamental circuits possible --
a minimum of resistors and other components to improve performance. The
well nuts, as they're called, which you reported having, IIRC, 8 of in your
fresh water tank should have one of the columns' nuts connected together
and back to the panel. Each of those in the second column should be
connected, by color code, to the base of a transistor on the panel. When
the water level reaches each of those individually connected nuts, current
flows between the common column and that nut and then to the base of the
corresponding transistor on the panel. When that base current flows, the
light bulb connected to the transistor illuminates to tell you that water's
at that level. The holding tank sensor system works the same and feeds,
IIRC, the same set of transistors, dependent upon which switch is
actuated. Because the height of the holding tanks is so low, there's
probably only one "common" well nut serving the 4 level sensor nuts. In
fact, my fresh water tank has only the 5 nuts rather than the 8 you
report. There's a good chance someone added the other 3 to try to improve
performance.
Performance is, at best, poor. The design was always marginal. The toll
taken by 40 years of corrosion of the sockets into which the transistors
are plugged, the development of current leakage paths on the board, and
deterioration of the various components all mean that you'll be lucky to
ever get even marginal performance from that system again -- the sense
currents are simply too low to be reliable, even under optimal conditions.
When I got my coach I spent some time and effort, including replacement of
all the transistors, trying get mine to work decently. Even my EE degrees
didn't teach me how to achieve that. It never worked any better than any
of the other systems I had over the previous 30 years.
Probably the most reliable, though not necessarily very accurate, indicator
system are those using capacitive pickups. That is, those with large
aluminum pads which stick to the outside of the tanks and are wired to
dedicated indicator panel. I've had some luck with those in the various
SOB's I've owned over the past 50 years. But, I'll readily admit that the
most reliable level indicator, for the fresh water, is a light behind the
translucent tank so you can visually check the level. For the gray water
(which we Coachmen owners are blessed with), the bathtub is the best
indicator -- when water won't drain from it, you PROBABLY need to dump the
gray water. I wouldn't even consider owning a GMC-fitted coach with
gray+black tanks.
RE: Water Pump. Over the past few months, thie mail order outfit listed
below has has a number of sales on water pumps suitable for GMC use,
especially FloJet and some Jabsco, both respected brands. I can't &
wouldn't try to, suggest a specific model, but I would suggest one with
specs of at least 40 psi and 2 gmp output. I would also seriously suggest
adding an accumulator to the system. I prefer a large (1+gallon) one to
the small ones offered by most pump manufacturers because they allow you to
use the toilet a time or two at night without the pump disturbing anyone.
The small ones only eliminate faucet flow variations -- still a useful
feature.
http://www.goldmine-elec-products.com/searchprods.asp
HTH,
Ken H.
> Hello All, hope your week is off to a good start.
>
> I'm making progress on the interior refresh of my 75 Royale. Still in the
> deconstruction and clean-up phase, I never realized just how challenging it
> would be removing 40 year-old carpeting with a million staples.
>
> I need to replace my fresh water pump, the unit in the coach hums under
> power but doesn't pump so I guess I'll need to replace it. The model is a
> Whisper King - Shurflo, 2.0 GPM - 30 psi.
http://www.gmcmhphotos.com/
> photos/my-75-royale/
p61672-water-pump-2.html
>
> What do you suggest as a replacement?
>
> Also, I used the through-the-floor drain to empty the water tank in order
> to remove it, I noticed what appears to be another line that enters the
> floor with a tap. I don't know what this is, any ideas?
>
http://www.gmcmhphotos.com/photos/my-75-royale/p61679-
>
water-line-with-tap.html
>
> Thanks for your input,
> Regards,
> Mike
>
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