On 2006-10-05 13:06:14 +0100, The Natural Philosopher said:


Ours got buggered 18 months ago, and needed a new gasket which I
got...but in the meantime something seems to have gone wrong
elsewhere.. and I am a bit stumped.

What it consists of is a reservoir of water that goes to a pump, which
pumps at what must be pretty high pressure into a boiler thingie. The
boiler output goes to a steam valve that goes either to the coffee head
itself which has a pressure switch - seems to need about 2 bar or more
to let steam out - or the steamer pipe for frothing the milk.

The basic trouble is that nothing is coming out at all. I did get some
steam briefly.

I have checked all the easy to get at stuff - the valves and pipes from
the boiler to the valve etc..

The pump runs - well makes its buzzy noise - but seems to draw no water
from the reservoir, but that pipe is OK as I disconnected it and sucked
water up.

My guess is that something is scaled up in the pump or boiler area, but
without more than a trickle of flow..how to descale it?

Yes I have. A Krups one. Works well. Actually I think they all work
in much the same way.

Normally you should descale regularly so that this doesn't happen

At this point, I think you will have to disassemble and get some
descaler into the pump and pressure chamber in some other way.

The principle of operation is simple enough. There are sprung valves
on the input and output and the pump is a vibrating plunger. It's
similar to an aquarium air pump but obviously beefy.

Another thing that can have happened is that one of the valves has
failed or there is some crud under it. That will involve disassembly
as well. Take care because there are probably ping****its inside.



What I also don't understand is why the pump seems to be configured to
run ONLY when making coffee - not when steaming or topping up with hot
water etc..is it that the high pressure an flow can only be provided by
a pump. whilst hot water and steam can be gravity fed?

What happens is that some water is kept around and boiled and opening
the steam jet valve causes it to be forced through the jet. There is
normally enough water to heat the amount of milk needed for a few cups
of coffee. You will find that if you run the jet for longer it will
probably run out. Some of the larger Gaggia machines have a separate
pump arrangement for the steam generator.





Normally I wouldn't bother, but its the wife's BIRTHDAY...;-)

Ah, so it could even be a trip to Newmarket to do business with your
favourite Currys shop ;-)