air con fan / cooling fan random start up

[locoboy]

Guys i have tried searching but to no avail,.

For the last 18 months or so now my car has intermittantly started up the aircon / cooling fan when i switch it off.
Its a 2.1td estate 1998 if that makes any difference

Here is how it goes,

Drive home from work - about 15-20 min at 40-50mph, car is normally just showing 70 deg on the guage, no air con on and i pull up outside the house, get out and open the gate (no fan noise) pull on the drive shut the car off and get out to just hear the fans whirring and winding down.

It does not do this all the time, last summer i drove into a post and broke the fan housings and pushed the rad back onto the engine and needed a new rad, when i ut the air con on the fans rattle like mad on the broken housing so i dont use the air con, i will fit some new fans for this summer, so when the fans start up now its really obvious and it happens i guess 2-3 times a week.

Now tonight i did the same routine, open the gate, no fan noise, pull n the drive, and stop the car, and the fans spool up and then shut off when i shut the engine off.
But tonight i went and shut the gate, let the dog out the boot and woosh off they went on their own!
I left it and they ran for 30 seconds so i started the car and shut it down again and 10 seconds later they went off again!
I was getting worried now as i had visions of them coming on of their own accord and running the battery flat.
So i played with the ac switch and it made no difference, fans still running and i started it up again and they went off then i shut it down and they are (well i think so!) still off.

Has anyone else experienced the random fan actions?
Or has anyone got any suggestions as to where to start looking or what could possibly be at fault?

My temp guage never reads into the hot zone and the fan will kick in when towing etc and then cuts off as the temp comes back to normal - so it appears to be ok temperature wise.