Cooling fan/air-con fans operation?

XantiaMan · Post by **XantiaMan** » 01 Jul 2008, 17:25

What is normal behaviour for cooling fans to come on? My car with the air-con on always has the fans going at a low speed but even when the car gets hot, they never increase in speed. With the aircon off the fans will come on an just over 80 but again, they are at a low speed.

A couple of months back i was treated to what sounded like a 747 taking off! The fans were at literally warp speed. This was after sitting in the sun for 30 mins, it was a hot day...i've never heard them running at this speed since. Should the fans ever run at full speed?

Taking the beige coloured plug off the stat housing will make the fans run at full speed, but then the air-con wont work in this state for some reason. Plug it back in and the compressor turns on again.

Some explaination as to the normal fan operation would be very helpful.

Gareth

Post by **RichardW** » 01 Jul 2008, 21:09

Fans at slow speed when:

AC on pressure normal
Engine temp above cut in temp (pretty low on my 97 A/C car)

Fans on high when:

AC on and pressure goes high
Engine temp above high cut in point (105 or something)
Brown temp sensor open circuit.

Sounds like yours are working normally. I got the fans in my HDi on high by switching the A/C on on a sweltering hot day when the engine temp was already 100 °C.

Post by **admiral51** » 01 Jul 2008, 21:19

I would say that yours are operating as they should like RichardW says

I think the reason the A/C wont work when you unplug the connector is that the A/C HP-LP switch will prevent or switch off the A/C if pressure too low (wont start) or too high then fans go full speed and A/C switches off.
As the fans are already running at full speed and bitron unit is receiving an open circuit fault (default setting fans full speed) then the A/C is shut down or in your scenario wont start
Well thats what i think........................................

Colin

Clogzz · Post by **Clogzz** » 02 Jul 2008, 13:09

Well that’s what I think

Thinking seconded.

At the high fan speed, the compressor is turned off to prevent the condenser from adding more heat.

From the peugeotlogic site:
http://www.peugeotlogic.com/workshop/ws ... fanop1.htm

The following tasks can be performed by the control unit: Switching of the fan relays, illuminating the "STOP" warning light, illuminate the warning light on the temperature gauge, prevent the A/C compressor from operating under extreme engine temperature or under full engine load, timed post cooling when engine is shut down with the fans operating.In order to carry out these tasks it receives inputs from the coolant temperature sensor, the air conditioning control panel, the refrigerant pressostat and the engine ECU.

oscarloco · Post by **oscarloco** » 04 Jul 2008, 17:24

Sounds normal to me. Fans on my ZX work the same way. I've heard them at "warp speed" only a couple of times, after the car was turned off being hot but not enough for the fans to come on and turned on after a little as the coolant temp has gotten to the critical point.