156=air con on=radiator fan on=normal??

[ducman]

Whenever the air con/climate control is on the radiator fan comes on shortly after. Even if the engine temp is low. For eg. when starting car from cold fan will come after a couple of mins if the a/c is on. Or coming off a motorway-engine temp only 60-70 get to first traffic light and fan willl come on. Turn off A/C and the fan will go off again. Is this normal???
Cheers,
Dave

[francistaria]

In is very normal, the fan starts due to the hp in the a/c system to
condance the refrigant.

[ducman]

Thanks so much Francistaria, really apprciate the reply. Not sure i fully understand though. The radiator fan comes on to condence the refrigerant? I thought the fans just pushed air over the radiators are they also conected to the a/c compressor???
Thanks in advance,
Dave

[James76]

2 radiators, one is the normal one for the engine coolant, the other is the air conditioning condensor.

Like round the back of your fridge, it needs air over it to cool the refridgerant, as it's sitting next to the engine radiator at 70 - 80 degrees. If the air - con is on the fan will keep cutting in, if it's a very hot day it will be on if you are travelling at low speed practically all the time.

[Chris Nason]

Two radiators (A/C & Engine), One fan. The circuit is switched by the ECU depending on Engine Temperature and/or A/C pressure (which is a factor of how much it needs to be cooled)

When you first switch the A/C there is quick pressure build up so a signal is sent to get the fan running. All this regardless of the engine temperature.

The low speed circuit switches the fan through a resistor mounted on the radiator. This resistor passes more current if the radiator is hot. This means on a hot day the low speed circuit is nearly the same speed as the high speed.

The high speed circuit just passes current straight to the fan and is switched (by the ECU) if the engine temperature is getting high or the A/C pressure is getting high.

The whole ECU/Fan circuit is switched on the negative side. Positive goes straight to the other side of the fan terminal through fuses.

[ducman]

Appreciate all the replies guys-mind at ease now-many thanks