1989 Dynasty 3.0 liter : lost the vacuum signal to shut off the heater hose supply of hot water to cabin. I believe that the signal comes from the Heater A/C temperature Control Switch ( lever arm ) on the dash.

I want to trace the vacuum signal to its origin ( I suppose at intake manifold).
Can anyone pinpoint where on the intake manifold this vacuum hose is connected?
Perhaps mine was disconnected at the intake manifold. Hope so.

 

Yes it is manifold vacuum..Bill

 

I believe that the vacuum source for the interior temperature control unit originates at the vacuum brake booster as a thin black vacuum tube running from the vacuum brake booster through firewall to the interior dash temperature control unit.
If anyone knows differently , kindly advise.