126 Windshield Vents Getting A/C Vice Ambient in "split" position
 

My '91 350 SDL just started to blow conditioned (cooled) air to the windshield in the "split" switch position ... i.e. the position to the left of the econ position which is supposed to pass a/c air to main vents and un-a/c air to the windshield is blowing conditioned (cooled) air to both.

Here in muggy Virginia, the easy indication is that the cooler inside air blown on the inside of the windshield causes the moist warm air outside to condense on the outside of the windshield ... necessitating a swipe with the wipers to remove.

I recently repaired (put back together and resoldered) my OVP relay in the car ... any chance this would have any effect? If not, then likely a vacuum line or some other duct issue?

Thanks in advance for any advice.