The problem is that within a few weeks the carpets (expecially in on the
floor next to the stove/sink. etc. on my Westy, look dingy again.

mark,

try running a second and possibly third cycle without any soap or
cleaner in the machine, just straight water.  the soap residue left behind
by most carpet cleaners tends to be sticky and attract dirt quickly to the
area you just cleaned.

jonathan