Thermostat sensors (fans issue).

[VeiRoN]

Hello,does anyone know exactly what the sensors on the thermostat housing do? fans won't kick in when the water temperature goes more than 3/4 so was wondering if a fault sensor could cause this issue,thanks.

[Bedford126]

green sensor controlls the ecu/icv. blue one is for the gauge cluster and the brown is un-used.

[Gandi699]

As above although the mk1s are controlled by a radiator based sensor outside of ECU control. Test the fans by running power to them directly

[VeiRoN]

Sorry didn't even write what engine is,it's a VTS 1,6 16v Mk2.

The fans do work Gandi,if you press the A/C button they work just fine.

green sensor controlls the ecu/icv. blue one is for the gauge cluster and the brown is un-used.

So i would exclude these sensors,could be a fault relay behind the front bumper then?

[Bedford126]

Sorry didn't even write what engine is,it's a VTS 1,6 16v Mk2.

The fans do work Gandi,if you press the A/C button they work just fine.



So i would exclude these sensors,could be a fault relay behind the front bumper then?

Yes, The fans run on a second relay for the a/c( from what I can remember I have only seen one with ac) so this would explain why they work on the a/c switch and not with thermo switch in the rad or the green temp sensor.

[Gandi699]

A/C on a vts? rare! WHat does it do if you unplug the green sensor when the car is running? Most ECUs power up the fans in this sitation as it doesnt know the temperature of the coolant

[VeiRoN]

Yes, The fans run on a second relay for the a/c( from what I can remember I have only seen one with ac) so this would explain why they work on the a/c switch and not with thermo switch in the rad or the green temp sensor.

Thanks,very helpful.

A/C on a vts? rare! WHat does it do if you unplug the green sensor when the car is running? Most ECUs power up the fans in this sitation as it doesnt know the temperature of the coolant


Yes,it's an Italian VTS so it has A/C,i know in the Uk they are rare.

I only tried to unplug the brown sensor,it sets the fans to the max speed as soon as you turn the ignition on.

[VeiRoN]

Just wanted to let you know that this has been sorted out,it was a relay behind the front bumper,not sure wich one as i unplugged all 3 of them,cleaned them off using an electrical contacts spray and plugged them in,now the fans works fine.