Arc Systems here! as John says you may well have a micro switched pump so open a tap that works the pump just enough to get the pump running, then open a tap that does not have water flowing and see if water comes from it now. If it does then you will most likely need to change the offending mirco switch in that tap head, however, first check the wiring connections under the sink for corroision.
As for the Cascade, the good news is, 1994 is by far the best vintage for this heater! don't no why but they certainly have less problems than all other years!!...any ideas John?
Heres my overview of the Cascade which should answer the rest...
The Carver Cascade 2 is a 9 litre storage water heater, which
when running on gas will heat the water to 65deg c in about 45 minutes. On 240V
mains assuming it has this facility, the time can be somewhat longer or shorter
depending on the wattage (630w 3amp to 840w 5amp) of the element fitted, you
can use both gas and electric together for faster times.
To operate the gas there is a wall switch or a switch within a main control
panel, either way both have three lights green, amber and red. When switched on
the green lights, (water tank must be full, i.e. water coming from hot taps),
if it stays on after about 8 seconds then the gas has lit and all is well. If
the green is joined by the red then you may have a problem, but if the gas
bottle has just been changed then air in the pipes will have to be bled through
by repeating the above 2 or 3 times. Once lit, and it should light without any
pops and bangs, (this would indicate it needs a service), the heater looks
after itself and gives constant hot water. Any problems will cause it to shut
down safely and show the red light. Forget the amber light, it's to show low
voltage and won't light unless the voltage is so low the heater and everything
else packed up long since, though you may notice it 'flash' as the switch is
turned on or off.
The 240v immersion heater if fitted is totally separate, and lies behind a
white plastic box on the inboard end of the water tank. It is controlled by a
switch, often close by and at floor level, but again sometimes as part of a remote
control panel. The switch has a red light to show it's 'on', not that it's
working, this will be determined by the water getting hot. If it does not then
it may have 'tripped' Two types exist, early circa 1990 are non-re-settable but
are repairable. Later models have a Red button on the end of the plastic box
which is sometimes behind a little flap. Switch off mains, and press to reset.
Other faults concerning the gas side very often come down to the 'Burner
Module'. This handy little unit contains the burner, gas valve and all the
electronics which control it and is accessible from behind the cover outside of
the van. In the event things go wrong it's a 5 minute job to replace it, with a
new or serviced exchange unit. One other safety device is a wax filled
'fusible' plug, this again is behind the outer cover and shows itself as a 13
mm nut set in the fins above the burner. The wax will melt if things get too
hot allowing hot water from the tank to spray over the burner and put the flame
out. This will render things safe but will require a new module because it's
control circuitry is faulty. However given if the fuse 'blows' without the
water apparently getting to hot then replacing the plug will be sufficient. The
point to note here is that over time the wax in the plug degrades or the
threads leak, at the very least allowing water to seep onto the burner causing
it to rust and eventually will still require replacement of the whole burner
module.
Further problems that come to light in spring is the discovery of frost damage
to the water tank, the non-return valve which is part of the cold water inlet
and other plastic fittings. Failing to drain the heater when there is a chance
of temperatures dropping below freezing can be very expensive to repair and
should be avoided by removing the drain bung and allowing the heater to drain
completely. Later models have a valve above the drain hole in the top left
corner of the flue cowl, these have a 'toggle' showing that when turned a ¼ in
any direction will allow air into the tank and assist the draining. Older
models still have the valve but the flue cowl needs to be removed and the valve
end pulled to open it, in this case opening all taps in the van will do much
the same thing. It is most important that the drain bung is then only placed
back into the hole and not screwed in, any water left in the system can then
drain away.
Frost damage to the tank will be obvious by the leaking water from the damaged
seal, the damaged non-return valve quite often will prevent water coming from
the hot taps although the cold water flow will be fine. Other fittings are
often cracked by the pressure of the frozen water and will leak on refilling
the system.
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