405 radiator cooling fans stuck on.

Overly simple i know but on the radiator there may be a simple temperature switch which operates the relays. If it fails then it probably puts the fan on as a safety default?

usually you can check the operation using a multimeter.

Check to see if you have continuity at room temperature.

then make up two little wires with clips and put it in a kettle and boil it, if it changes then it works.

started both radiator fans are running.

fan relays which are OK.

well as both sensors in the thermostat housing). I have tried to trace all the wires connected to the three relays, little success due to peugeots numbers on the wires being difficult to find.

activating the relay, I ca't find where this wire goes? The wiring diagrams in the haynes manual do not cover the control from the Bitron Aircon control unit.

would be very useful.

As you have possibly found, the fans run at two speeds. This is done by the three relays you mention which either connect the fan motors in series or parallel. As soon the aircon dashboard switch is on, the fans run in low speed. This is nothing to do with temperature sensors or the Bitron controller. The high speed is enabled when the engine is hot and maybe when the aircon is working hard. I'venot been able to find out the exact criteria for the top speed.

Could it be that turning off the aircon will fix your problem?

The wiring diagram in the pale blue haynes manual seemed accurate when I was fiddling with fans a couple of years ago.

hth

Bob

Thanks for the input, I eventually cured the fault after finding a post on this group relating to the same problem.

The problem was cured by disconnecting the two Bitron large round connectors on the nearside inner wing. Sprayed them with W40 and reconnected them.

I guess the fault is due to a poor contact sending bad information back to the Bitron control unit and hence turning on the fans.

Hello,

One criteria is heating up. For example, first speed engaged @95°C, 2nd speed @105°C. I guess my example values match a 205 TD.

Regards, G.T snipped-for-privacy@worldonline.fr