George,
Thanks for the reply. This is on the 83 Wagon. Emissions bypass has been done on both the the 83 and 86 so the MCU is out of the pic. The 86 engages the sol vac w ac, headlights or rear window defog. Rear window defog is inop on the 83 but it used to work for both ac and Headlights. In the 83 TSM, pg iJ-38 it says the holding sol is engaged if hl, ac or rwd are energized. In the 86 TSM, pg B-301 wiring diagram, it shows separate wires fm the systems to the sole vac but doesn't show where they come from...wiring...agh!