Hi everyone. I have a Mk1 1.6 auto and the fans are not kicking in so it is overheating.

It is not the resistor, or the fans, or the relays, or the fuses.

low speed fan is not kicking in and the high speed is not as well.

I put a new temp sensor in it and no good.

When I disconnect the temp sensor and start the car, both low speed and high speed relays kick in and fans run on high speed so I assume wiring is all good.

I am really at a loss now on what it could be.

I know this is a very common problem, but I have exhausted most of the common fixes.

Please help.

Hello, Did you ever get your problem solved?

Have exact same problem.  Checked both fuses (F2 30A & F6 50A), tested Both Cooling Fan Relays (Level 2 A/C & Level 1). All good.

Disconnected the Temp Sensor, start the car, fan starts with low speed then switches to high, so seems to confirm all that I've tested so far is good as well as the wiring. 

The top radiator hose heats up then the bottom one, when the diagnostic tool confirms the engine temp is around 95. So thermostat appears to be functioning correctly. Cylinder head Sensor (one doesn't exist on the radiator) shows temp as normal (straight up), changed the sensor which made no difference. Engine overheats @ chucks out steam & water @ 114 degrees, despite the gauge in the car saying its still normal. Fans do not work with A/C. So fans only work when disconnected from CHS which is new. No engine error codes. New cap also added. Have done a block test which confirmed that the head gasket is good with no leaks.

Any help would be much appreciated.