Cooling fan operation

[crad2]

Hi pug experts. I have a 406 with air con. Only one fan comes on at full speed when hot. Have checked all relays which are ok and both fans work at slow speed if i bridge one of the relays. Cant find any infomation as to what controls the relays as they are not switched directly by the sensors in the thermostat housing. From what i see on here both fans should run when air con is on, they dont.
Any ideas appreciated.
Thanks.

[mjb]

They should come on intermittently when the aircon's on. Also, be aware that on D9s, there's no "on" setting for aircon, only "auto" which is able to turn it on and off as it deems necessary to maintain temperature+humidity in the cabin.

That said, full speed operation shouldn't happen too often if you've got 2 working fans.

Some models have 2 or 3 coolant temperature sensors - one for the dash, one for the dash over-temperature light (on only a few models, and you haven't said what age+engine you've got), and another for the ECU. It's the latter that ends up controlling the fans, so check you're looking at the right thing. With the engine running but cold, pull the connector on the sensor. Either your dash gauge will drop to 0 or the fans will spin up to full power. If the latter happens, I guess you've either got a wiring/relay problem, or the Bitron ECU mounted in the nearside wing has given up the ghost. I'd hit a breakers yard and grab a new relay+bitron ecu...

[crad2]

Thanks very much, sorted. Wiring loom to that bitron module under the wing had water damage, over time one of the wires in the loom had corroded through somehow .
Cut out and joined in a new piece works fine. Took 4 hours to find it out though!!!
Silly place to put it.

[crad2]

Found this, its for the 306 but looks the same. Might be of help.
http://www.peugeotlogic.com/workshop/ws ... fanop1.htm