Having problem getting the vacuum to the heater / AC controls to work correctly.  Losing vacuum.  Has anyone found / designed a replacement (Say electronic) to replace the vacuum control?  What other alternatives are there, if any?

Is this a recent issue that has occurred or an existing condition that has never been addressed?  The reason I ask is in the past I've encountered vacuum line that were leaking due to age which effected heater/AC controls/functions. In some cases it was just a matter of gaining access to the hose(s) in question and just clipping a bit off the end due to minor splitting that had occurred with age.  Afterwards in most cases all worked as it should. If you don't have a '67 SM I recommend you secure one it have all the vacuum schematics.   

Edited August 12, 20178 yr by SPRINT 6