Cooling fan stays on

[mjk164]

1993 960 24v 214000 mls.
One day this week I found the cooling fan running after I had switched off the engine....well sometimes it does this for about a minute or so; only this time it did'nt switch off and drained the battery. I first suspected the fan relay situated just in front of the battery. I had it off, removed the cover and cleaned up the relay contacts. These are quite easy to get at on this unit but you need a contact burnisher which is nothing much more than a rather dull small file, and finish off with some very fine crocus paper. Put it all back and tested but the fault was still there with the fan still running. Now went to the aircon pressostats which are at the front of the condenser at the bottom, behind the radiator grill. There are three of them here; the outside one is purple and is the high pressure shut off switch, the middle is grey and is the low speed pressure switch and the one closet the center line is brown and is the high speed pressure switch. The grey and brown ones are connected direct to the battery and will operate the fan via the relay independently of the ECM or ignition. By simply removing the connectors in turn I identified the brown high speed switch as being faulty since the fan stopped on removal. Down to the best Volvo agents in London Braydon Motors for a 2nd hand switch and job done. Be careful when you try to remove these switches. There is a Schrader valve between the switch and the aluminium manifold which houses all three switches which alloys you to remove the switch without loosing the a/c gas charge, but you must use two spanners, one to hold the smaller flange nut against the manifold and the other larger one, to unscrew the switch.