I've asked this question on numerous sites
 

But unfortunately with no real answer:-

Has anyone else had this happen?
On starting the car, in the morning, the fan switches on and operates in fits and starts. All heater switches are off. This doesn't happen after the car has been stood all day, just in the mornings.
The fan stops after about 20-30 seconds.
Any ideas?
Thanks in advance.

WHAT YEAR CAR ARE WE TALKING ABOUT?

1995 993 Cabriolet.

Have you tried posting this on the 993 Technical Forum?

Is it something to do with the heater blower relay? I know my car is much earlier than yours, but I used to find that my heater blower would work eratically, so I took the relay out, removed its metal cover and cleaned it, popped it back together, and my problem was completely fixed. Dunno if that's any use to you or not.

Are you sure it's the fan motor? There is an air pump that runs for 30 sec to 1 min upon cold start only, helps the cats start up nice for min cold start emissions.

David E Clark: Yes.

CharlesJones: Thanks, I'll look into this solution.

silverc4s: It's definitely the heater fan, you can feel cold air from the vents and like I said it's sporadic, starts, stops, starts again.

Thanks for the suggestions.

I've been to that forum and left when the third tumbleweed blew by.

True. Not much going on in there. On the other hand, there are a bunch of guys on here with 993's.

Do you have an owner's manual? It could be some "normal" condition that the manual mentions should happen when the car is cold.

I have the Adrian Streather 'Essential Guide', but haven't seen any mention of the subject as yet.
I've considered the "normal" condition, but it's the sporadic nature of the fans operation that concerns me, that doesn't feel "normal".
Thanks for the input, I'll keep searching.