On our '88 the temp control OFF position is at 6 o'clock. Counterclockwise turns on the heat.Just to clarify, when you say just crack the heater control to keep flow going thru the heater matrix. The 5 o'clock position on an S4s is wide open heat. So I assume you mean just off the cooling range into heating zone?
So if your S4s is different, just move it a little past the OFF position.
Send a picture!??!