Hi guys, got another problem with my fans (again)! I've done some searching of the other fan related threads, but i'm not sure if any really cover the same issue as mine. Basically, the external temp gauge has been all over the shop recently, sometimes reading over 40 degrees!

Now, one particularly hot day (the glue on my tax disc holder even melted), I jumped in and cranked up the air con, and it worked for about 10 seconds then kaput. Nothing. I cant even manually turn the interior fans on.
I've had a look at the relays, and whilst one was a touch corroded (the bottom/middle one), I cleaned it up and put it back in. When I tried the air con, after about 10 seconds, the fans (both) kicked in, but immediately switched off and slowed down to a stop. This then happened repeatedly every 30-40 seconds or so.

I've also tried taking the red plug off, but nothing happens. So, i dont know whether it could still be the relays (i might just get three new ones anyway), the bitron unit, the external temp sensor or the coolant sensor, or the fans themselves (unlikely imho).
Any help from anyone would be gratefully received!
Cheers