i thought that the one marked with a fan is the one for the heater blower, bizzarely. are you sure? run the blower and then pull out the fuse marked by the fan and see if it stops.

your fault still sounds like the common melted fuse box. the switch is clearly working the relay, but the relay either has no feed to switch because of melted corruption, or the output can't reach the fans cos of melted corruption (can't remember which way around it is). i had exactly the same problem.