<E28> heater HOT or COLD, no warm, need advice

[bolhuijo@xxxxxxxxxxxx]

 As soon as one turns the thermostat up off the peg, the heater comes
on full blast.  A VOM on the heater control valve reveals a full 12V
keeping the valve shut all the time, except when one dials up any
temperature greater than full cold, at which time it opens up fully.
 This happens regardless of actual cabin temperature, as far as we can
tell.  Is it possible that the cabin temp sensor has gone south?  It
should be much easier to replace that than the rheostat assembly.
Also, can somebody verify that the temp sensor is the gizmo stuck
inside the underdash trim piece with the 3-wire connector and the
vacuum hose?
 I haven't yet gone to disassemble the dash to do any testing of the
rheostat, as that's a PITA, and I'd rather ask for advice first.  The
FAQ doesn't seem to cover anything but broken control valves, which
mine ain't.
 I'd be glad to summarize any solutions here, as it is getting colder,
and I can't be the only one with a half-working heater...

- --
  John Bolhuis  | Since announcing concubine auditions in April,
 bolhuijo       | I have received not a single reply. Foolish females!
  @domain.elided | Do you not realize that I am one of the richest and
                | most powerful men in the Republic?  -T. Herman Zweibel

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