been working on this problem and reading posts [1998-now]in this group
for the last few days.  have tried all i solutions i thought could be
prob.  on def, a/c comp is not running, [not serviced] fan runs, aux
pump  is running. mono valve looks good, clicks with external power,
but has no power to it when on def. i took off the hoses, and could
pour water in one outlet and out the other. so i assume it is in open
position. i have taken all 3 hoses off nipples on firewall and supplied
light flow by garden hose [i suppose they are attached directly to
core, right?]  all flow very freely.  end nipples seem connected
inside, put water in one, it comes out the other.  put water in the
middle it comes out both sides.  put back together,  with engine at 80c
and system pressure built i get hot pressurized hose from rear block
to center nipple.  but both outside hoses soft, and somewhat hot.
squeeze either and i can hear some flow, but not much.  zero warm air
at dash.  which way is the water circulation going?  from rear left
side block to center nipple and then to mono valve and then to aux pump
then to water pump as i assume?  can my heater core be hot and i have
some valve closed to air flow under the dash?  i appreciate any help,
suggestion on this,  i really want this heater/ ac to work.  havent
tackled a/c yet.  -gary