[EC900]

One the same problems I once had.
Both Fog and R. Defrost dash knobs would light up but neither were activated.
Found the Fog lamps were disconnected along the front cowl, maybe snagged at some time caused the terminal pulled apart.
The fuse for the rear defroster is in the engine compartment along with relay were good. But more common problem might be wires are not connected or terminals broken off, often result from reinstalling the rear windshield.
I still haven’t yet addressed my R. Defrost yet or which of the 3 stages work or don’t since I’ve yet to fog up the windows last winter. Not sure how to test either.
I have a Pelican post on the wiring bookmarked somewhere - if I find that I’ll post link.