heat control issues

[meuhus]

hello all

i have just purchased a 1997 astro
heater selector didnt work fixed vac line
now selector works but only blows cold air
unplugged vac line that plugs in under heater box in engine
compartment near vac res ball
and have heat
is there something inside the box that is not working properly
like a vac operated vent door

thanks

[brcidd]

Your temperature door is controlled by an electric actuator, not vacuum- check to see if axle of actuator moves with increasing/decreasing temp setting (with ignition on) - if it does, then actuator is ok-- remove actuator- and see if temp door is attached to axle- rotate it by hand, does it feel like it is moving the temp door? Actuator is on RH side of HVAC housing

[meuhus]

so take the box in the engine compartment
apart
i cant see anything like your are describing
in the engine compartment

[meuhus]

hello again
just an up date
sorry to all this may seem trivial too
but not familiar with the astro
i crawled under it and the vacuum line i dissconected was to one of two
vac. controled water valves. it seems that gm added every thing to make it have rear heat
then sent it to an up fitter (mark 3) they didnt add the rear heater controls or rear heater core ect.
the vacuum line i disconnected was from the lower of the 2 valves (it has the vacuum diaphram on bottom of valve).
the upper water valve doesnt have any vacuum to it(it has a diaphram on the top of it)
the heater temp selector works fine as long as i dont hook up to the vac line to this lower water valve
should the upper water valve have vacuum present all the times
the lower one doesnt have vacuum all the time i forget when it is present
is there any vacuum diagram avalible for this?
is it possible to finish adding the rear heater with out being a big pain

[brcidd]

Those are heater shut-off valves- they are designed to block hot water flow to the heater cores when you select "full cold" on the temp selector. There should only be vacuum there when in full cold-

Exercise the upper (front) water valve lever arm- they can tend to stick- test for yourself- you get heat when valve is open, no heat when closed.

Normally folks complain that their cooling ability is amiss- because the water valve does not shut off- you have the opposite problem.

GM did not send those vans to the upfitter-- the Upfitter bought them from GM- and then marketed through the dealers- so anything the upfitter did is out of GM hands-- I always hate to wotk on upfitted vehicles- you can't ever get a service manual style reference for them- who knows what hey have done- at one time there were over 2000 upfitters in the US- probably about 20 now....

[meuhus]

so can i lube this thing up or does it just need to be replaced
yes it it sticking when the vacuum signal is gone
not opening

is it possibe to get the rest of the rear heater controls
for the van
would like to add the rear heat my self
heater hoses are ran to the middle row of seats on driver side
what else is needed to have the rear heat