Hi all, I have the same problem with my 2001 boxster.
I got caught in the rain last fall, it was a deluge... up until then everything worked fine AC/heater motor at all speeds.
The next morning nothing... nadda... you know the rest.
I bought a Bentley's manual and just pulled my car out of storage.
Checked the fuses by pulling them, check with my test light for power at the fuse box all is ok.
I am trying to figure out how to test the heater relay. any ideas?
I also tried removing the the right hand vent pipe to get to the blower motor to check for power at the plug but I am afraid to yank on the pipe and break it as it is a tight fit.
The manual does not show any details
Thanks.
TC