[Jules]

Originally Posted by slimsi

I have now had my temp gauge a few weeks and I have some interesting findings, basically when I am on the motorway with the AC on or off the temp is always between 80-90c.

What interests me though is that when in stop start traffic like the queue for the blackwall tunnel with the AC on it will rise to 90 but no further, with the AC off it will raise to 104ish and then drop back into the 90's.

My presumption is that with the AC on the fan runs constantly and keeps the temp down? Anyone else see this?

Simon

80-85 Deg is too low IMO Simon indicating the thermostat not doing it's job fully.
With Aircon On or OFF the thermostat or PRT should compensate until it is fully open. A further temp rise should see the fan kick in at approx the figures below:

OPERATION

K1.8

Engine Running
If the ECT sensor registers a temperatures of;

Between: 98 °C and 104 °C, = Low fan speed
Between 105 °C and 112 °C, = High fan speed

The ECM switches both cooling fan relays off if the ECT sensor registers a temperature of 98 °C or lower.

Engine Stopped:

Above 112 °C = High speed relay

The cooling fan motor is now able to operate at high speed until the ECT sensor registers a temperature of below 112 °C.


KV6


If the ECT sensor registers engine coolant temperatures of:

Between 96°C and 100°C, = Low fan speed
Between 102°C and 106°C, = Medium fan speed
Between 108°C and 112°C, = High fan speed

Air Conditioning Request
If air conditioning is requested, the cooling fans will automatically operate at medium speed, even if the engine coolant temperature is below 96 °C. If an air conditioning request is received by the ECM when the cooling fan is running at low speed (i.e. the engine coolant temperature is between 96 °C and 100 °C) the ECM will increase the fan speed to medium. If the engine coolant temperature rises above 108 °C the cooling fans operate at high speed as described previously.


M47R Diesel

If the ECT sensor registers an engine coolant temperatures of:

Between 100°C and 105°C, =Low fan speed
Between 106°C and 111°C, = Medium fan speed.
Between 112°C and 119°C, = High speed.

For 2 speed motors IIRC the ECU energises SLOW speed for a larger temp span.
For example in the diesel engine:

From 100 Deg C to 111 Deg C = Slow Speed
From 112 Deg C to 119 Deg C = High Speed

Taken from RCL 0311ENG
Please bear in mind if you are relying in the On board diagnostics for readouts, this assumes your Temp sensors, Thermostats etc are still in Spec, all these devices change value/tolerance with age