405 cooling fans

Post your Cit/Peu/Ren air conditioning queries or advice.

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405 cooling fans

Unread post by citroen7 »

can anyone help ! the fans on my 405td (with aircon) come on when they like
i found a couple of posts that pointed me in the direction of the relays so i changed all 3 ,with the car running the fans stay off until it is up to temperature they then cut in and out at about the right temp,but as soon as you turn the ignition off they kick in again.If you then turn the ignition to the second position they go off. i tried disconecting the biriton sensor but it didnt do anything so i changed the sensor with one off a xantia with the same engine and on disconection the fans kicked in ,so i thought great fixed . Yesterday my wife rang me to say the fans were running and this was the middle of the afternoon and the car had not been moved since 9pm the night before!
so please point me in the right direction.

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Unread post by AndersDK »

Moved to the french aircon forum, as you are much better off with advice from here 8)
I bet its a problem with the brown Bitron sensor ...

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Unread post by DickieG »

I imagine you have a problem with one of the relay earth wires, take a look at the following link for further info, I'm not sure but I imagine that a 405 will have the same wiring diagram as a 306, I know Xantia's do. http://www.peugeotlogic.com/workshop/ws ... fanop1.htm

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Unread post by Clogzz »

With the Bitron disconnected, the brown coolant temperature sensor, the air conditioning switch and the aircon pressure sensor switch cannot operate the fans.
The fans go to low speed when the ‘left fan relay’ is energised by the Bitron earthing its pin 2, while pin 1 is permanently supplied, even with the key out.
So, it goes as per DickieG’s post, and pin 2 must be shorting to earth somewhere. :mrgreen:


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Unread post by citroen7 »

thanks for the info guys i have been playing around today and have got things to stop working on there own but the dodgy earth sounds very promising, i have also noticed a very tiny hole in the bottom of the rad so will order a new one its a shame the xantia rad is not the same i could have just swopped them!

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Unread post by steelcityuk »

I had something similar with my 405TD GTX. It was down to a blown fuse that whenever the ignition was on the fans ran at full speed. The fuse had blown due to a faulty airbag 'slip ring' connector.


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Unread post by stevieb »

Check the 30 amp fuses in the black box above the nearside wheel arch. They usually blow with cooling fan problems.

I found with my old 405td that the wiring below one of the relays had begun rotting. This was causing the Bitron unit to receive all sorts of weird and wonderful signals. Hacking the rotten wiring back a little and ensuring good contacts with the relays cured the problem straight away.

The snag is you'll possibly have to lose the existing connector and have to use old-fashioned blade terminals. Still, they're easier to coat in protecting vaseline, aren't they....???

I think the Bitron gets more than its fair share of criticism. The biggest problem it has is it's just too damned sensitive to glitches in the signal. Keep an eye on all the wires related to it, and I reckon it should be fine. My faults were all on this forum as "Bitron faults". As I say, it turned out to be a wiring fault.