radiator fan not working

hi guys just went for mot and car overheated, at 123dgreees on the info display , apparentlky the fan is not kicking in , what temp is it supposed to kick in ? and what would prevent it from doing so ? and what would be my procedure now to accertain whats up with it? many thks anthony

and just been out and checked and swapped the fuses and relays over and still nothing ? am baffled:angry2: :hissyfit:

Most cars have a switch in the radiator and I assume the Volvo is no exception. The easiest way to check if the fan is working is to disconnect the plug on the switch and short the 2 wires(this is basically what the switch does anyway but via a temp) and the fan should come on. If it does you have found the problem, the switch if not then the fan itself maybe the problem again testable(sic) by disconnecting and running a direct feed to the fan motor from the battery. If neither of those locate the problem then it is more involved

ok still wont come on , so what i did was connect teh live and earth directly to teh fan and it worked , so fan works fine ? so next problem is what tells the fan to come on? according to the manual its teh ecu? so what should i do now? many thks anthony

been playing with the sensors etc etc ,now on the info centre, it ssays oiland engine are always ''cold'' ,,, what have i broken now, think i'm going to have to scrapit if i can't sort these problems out

Hey mate, sorry you haven't had a direct reply as of yet. Take things back a step and first of all ask why your car was over heating in the first place, the cooling system should only require the fan once its been running a while i.e. up tp temp, and then stood without a coling air flow passing over the radiator, this can take some time as ususally you will be at tickover... So before we panic about the fan, take a look at the cooling system, is the thermostat openning correctly??? or is the coolant, cct shut making the coolant get very hot very quickly, is the coolant in good condition, should be a bright green color, minimum 33% ethylene glycol mix, up tp 50% for cold climate. Also do you have any airlocks in the system which will be preventing the colant circulating correctly, alternately you may have some blockage in the coolant system from debris / corrosion. To get back to a known position suggest you confirm / replace the thermostat, flush thoroughly the coolant system (fill from the resevoir and allowe to drain through the radiator, fill it up with plain water run it for a minute, then flush trhough again), and re-fill, ensure the remaoval of any air locks, run the car with the heater matrix open and fan blowing, squeeze all flexible hoses repeatedly to pump the coolant, continuously top up the coolant resevoir as you go.... Once you have done this or you are confident in the cooling systems integrity start looking at the temp sensor, (side of thermostat housing), manually swith this to send a signal to the ECU, then confirm it is switching the fan... if nothign from the sensor replace it, once done if nothing from the ECU then suggest disconnec the battery and leave for a nhour or so, re-connect and try again, if still no good check thereare no error messages on the ECU at the dealers... Hope this is of some help...

thks for that , will go through it in order shortly,but reason over heated cos it was sitting in mot bay for 30 minutes running , then it went overheated and dumped al lthe coolant out of the expansion tank

Overheating 

You don`t say what model this is [ not that that make`s much dif ] You can always run a feed via a switch to fan as a temp measure at least you should be able to use the car. The overheating seem`s to be just related to the sensor as a direct feed brings the fan on ,and this happend when standing ticking over for a long time , but not sure with ecu control`s [ sorry old school of mechanics ] the no of car`s of dif makes over the year`s that we have used this method as a temp or permanent fix For is vast. At least this is a reversible fix Regards Mike B

ok ive tried scotch blocking the connector near the thermostat and it still wont bloody switch on? am at wits end now?