The 'E' Type Forum

I have recently replaced pretty much the entire cooling system on my series 1 2+2 as the old pipes were corroded having been left empty. I also upgraded to a coolkat fan and a new header tank, with a coolkat solid state otter switch. I ran the car up to temp for the first time today, and the fan doesn't seem to kick in.

If I run the car at idle for 5-10 minutes, it warms up and indicates between 90-100 degrees on the temp gauge on the dash. The radiator and all coolant hoses get hot, and the heater blows hot, indicating that the water pump is circulating water. Yet the fan doesn't come on. A meat thermometer (!) in the header tank indicates around 86-85 degrees C. I then lost my bottle and switched off as I didn't want to let it get too hot.

If I connect the two wires on the otter switch directly, the fan comes on, so I know the wiring and relay are OK.

Is my otter switch faulty, or am I not letting it get hot enough?

Cool kat on temperature is 185f +/-5f

So I need to let it get hotter? This is measuring the temp in the header tank, presumably this is safe despite the temp gauge in the car reading 95-100? Is there another way of monitoring the temp whilst running it up to make sure it is safe?

Your assuming your car temp guage is accurate....get yourself an infrared tester....Steve

Something you should have done befor installing....test you otter switch in a pan of water on the stove testing its operating temp...and test your thermostat the same way

I'll remove the switch and test it...

If I get an infrared thermometer, where is a good place to test?

For checking thermostats and senders, I use a cooking / jam thermometer, a decent one, with the classic glass column, in a pan on the stove.

Or sometimes a kettle balanced on the cylinder head, if I want the real-life voltage feeds as generated by the car.

In my experience with infra red ones, you have to be circumspect with the interpretation of the readings as they are very dependant, and influenced by, the colour and nature of what you are aiming at.

Whereas jam is jam.

Issue finally solved - it was the old sender over-reading. After a bit of faff with stripped threads in the inlet manifold (see my other post) I installed a new generic marine sender after checking the calibration with a sous-vide cooker and some jump leads...

Gauge now reads correctly, and the fan comes on/off as expected maintaining a temp at around 75-80C.