Heater Question BUT not the normal one
 

Car has full heat all the time.
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The clips are in place on the servos.
The Heater valve is Brand New although the old one was also good.
The main controls have been swapped out for a known good one.
Fuses are all good.
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So here is what else I know when you slide the top lever the rear servo moves that lever just fine.

When you slide the bottom lever, you can hear a servo motor but the main servo motor doesn't move.

So what else can effect the servo? Can the servo not moving control the vacuum motors not allowing vacuum to the valve?

What else should be checked that might prevent the servo from working?

Thanks

check vacuum lines - no vacuum to valve causes valve to be open