406 cooling fans not working bitron unit - Carman55
i am having problems with my 406 cooling fans(1.9td with a/c) at the moment neither fan comes on even if the temprature goes over 105. i took it to a garage and they said both fans need replacing with a quote of £300 to have the work done so i thought i would look on this forum i found a previous post on the bitrin unit and located it in the car. when i unpluged the brown cable the drivers side fan came on at high speed (only when the ignition is on) but the passenger side didnt on closer inspection the passenger fan is hard to turn so i think it has seised. do you think the reason the drivers fan only came on when i removed the switch is because the bitron unit is faulty. if so would the car run on 1 fan if i replaced the bitron unit?
406 cooling fans not working bitron unit - RichardW
I suspect you only found the coolant temp sensor on the thermostat housing - the actual Bitron unit is usually well hidden, and despite lots of comments about them, they rarely actually seem to give trouble - it's unlikely the problem will be fixed just be replacing the unit. If only one fan came on with the brown sensor unplugged, then something is amiss either with the control relays or the fans themselves - both fans should run together always. Since the passenger fan is hard to turn and did not run I would start there first.
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RichardW

Is it illogical? It must be Citroen....
406 cooling fans not working bitron unit - R.Turpin
The fans run at two speeds. With air con on, or at low radiator heat, they are connected in series and run at half speed. If the water temp rises, they run in parallel, ie 12 volts each, at full speed. Sounds like a relay problem unless one fan motor has broken. It has on mine, but by altering the wiring I now have one fan at full blast whenever the temp reaches low. It has never overheated, even this summer.
406 cooling fans not working bitron unit - gsb
I had this problem with my 2.1td, only one fan working. So fast I thought the car would take off. After changing all the relays etc no difference. So bought one new fan and now all ok.