Ford Ka cooling fan/warning light inop

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Tue 20 Jul 2004 22:10
Ford Ka cooling fan/warning light inop - stuartmc
Hi, apologies for this....long story.

Car is a basic 97 KA and after a recent engine swap the cooling fan doesn't seem to be working (don't think it worked before either). Noticed that leaving the car on idle with the lid off the expansion tank the water boiled over without the fan starting or warning light coming on (lamp tests OK when ignition switches on).

Have run it since then for a few months long & short trips without any problems but have to have heater blowing hot in traffic to keep it cool and would like to fix fan/light. Coolant level has been rock solid so I reckon head gasket is OK so checked out fan circuit which is driven by engine management. Found thermistor under the manifold and replaced it but seems to be the same. Measured both thermistors in boiling water and they are about 3kohm. So tried 2,2kohm resistor in place of thermistor. Still no luck, but reducing resistor further to 1kohm and the fan starts. This suggests to me the fan drive/relay/power is all OK but maybe ECU is sick and not reading thermistor correctly?

The point of my question is - could the ECU have a calibration curve for thermistor which is now inaccurate? If so, can you clear the calibration? Do you think the car needs to meet it's maker?

Tks

Stuart
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Wed 21 Jul 2004 08:03
Ford Ka cooling fan/warning light inop - Andrew Moorey (Tune-Up)
Fan cut-in temp is 105 deg C. Fiesta and Ka suffer from poor sealing of radiator cap resulting in the water boiling at, surprisingly, 100 degC. I replace the caps at each main service. Inspect the top of the neck where it seals against the gasket in the cap. I have seen several with a nick out of them which again causes overheating and coolant loss. I dont think the adaptive learning strategy applies to the coolant temp sensor but you could try disconnecting the battery for a while to reset any adaptive values.
I trust you have replaced the thermostat?
Andrew


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Simplicate and add lightness!!
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Wed 21 Jul 2004 19:56
Ford Ka cooling fan/warning light inop - stuartmc
That explains the problem we have. It seems crazy the fan comes on so late - I thought most cars switch in at about 96? The only leak seems to be around the thermostat housing when under pressure so I'll change gasket straight away.

We did disconnect the battery in case it was adaptive. I reckon now that the fan circuit is OK, just didn't realise it switched in so late.

Tks

Stuart
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