Fan started whilst (indicated) water temperature was low. Why?

[green george]

I was tinkering in the garage this morning and whilst doing so let the car warm up,as it hadn't been run for a while. 

The ambient temperature was only about 3C.

After about 5 - 10 minutes I noticed that the radiator fan kicked in, but the indicated water temperature was still only just reading on the gauge so in the very low 40's.  If that is correct the fan shouldn't have kicked in.

I had a fiddle with the plug at the rear of the gauge without any change in teh reading; historically my water temperature gauge has intermittently read low but by moving the plug / wires has given a higher (presumably) correct reading. 

My 7 is a 2000MY 1.6 EU2 Super Sport K-Series engined car equipped with an Apollo tank so the water gauge also shows the oil temperature at a flick of a switch.  The oil temperature was not even registering; which is what I would have expected as the car had not been running very long and the ambient temperature was low.

Can anyone explain why this happened?

[Jonathan Kay]

Where are the two sensors?

I'd start by:

1. Rerunning the experiment.
2. Looking at the sensor/ switch, wiring and connections that control the fan: is the wiring intact and can you make it come on by wiggling?
3. Confirming that the indicated water temperature on the gauge still responds normally as it warms up.

Jonathan

 

[green george]

Hi Jonathan,

Thanks for the reply.  I will give these ago, but am on my way to work.

Re. 2. I will check the sensor / switch, but anticipate it is fine as the fan didn't come on immediately and when it did switched itself off apparently normally.

Re. 3 I will take her for a drive and see what happens during a run.

George

[Johnh]

If it happens again without water loss and you have no air trapped in the system..then try changing the rad temp switch first off ..they are cheap enough if you cross ref with other vehicle makes I got one new for around £4 from a Peugeot fit.. just make sure the switching temp is the same as the one you have (normally stamped on side of switch) and thread size also.

[Smithy77]

Tell help determine 3, easiest to have a 2nd means of checking water temp to see if the gauge calibration is correct. Either connect a laptop or OBD scanner to the car, or more simply, buy a laser thermometer (<£10 on ebay) to get reasonably accurate readings on various parts of the engine, i.e. water rail and top of rad

[DJ.]

Assuming the fan switch is on the radiator, the thermostat must have opened to allow warm water to reach the switch. That wouldn't happen until about 80 degrees minimum, so I would say the temp sender is wrong. Can't be the gauge if that showed the oil temperature correctly.