tucked away behind the left headlight is a fan control relay.Usually black plastic box.Take a look at the connector and wiring.Also check fuses in engine bay fuse box.

If you have not checked the temperature sensor usually in the radiator bridge it out with a link for testing,otherwise replace to test.

brueit

RE: Peugeot 406 V6 3 litre. Radiator fans failing to cut in when engine reaches 90c or above. Took it to garage specialising in Peugeots, they failed to find any obvious fault and said that after cleaning contacts on fan relays they got both fans going. Note relays are protected from the elements by a plastic cover.

Problem persisted. Took it back to garage who still couldn't find cause of problem. Eventually settled for a wired switch on the dash to overide system and turn one fan on. This isn't a solution I'm happy with as there's always the risk of forgetting to turn the fan off and then returning to the car to find a flat battery. More recently the air con compressor has gone West but I don't think the 2 are connected.

I'm reluctant to take the car to another garage as it's already cost £160. Has anyone any suggestions (other than scrapping the car)?

Many thanks for the reply.

I can see no black box behind left headlights. There are however 3 identical (5 pin, 12V, 35amp) relays situated in centre & front of the 2 fans themselves. The garage say they checked these. I've cleaned the pins, checked the connections, which seem sound & swapped the relays around. Made no difference. Fuses in the engine bay are OK).

As Puegeots are prone to electrical faults I suspect an electrical cause but not being an electrician doesn't help. I think I'll change the water temperature sensor as this is cheap to do, just to be sure that this isn't the cause; and if this doesn't cure it then I think I'll have to find a good electrician.

Thanks again RichardV