Thermo fan problem

[Chas Uno]

Haven't had a lot of time to look into this, but wonder if any electrical wizards can point me in the right direction. The problem is as follows:

The thermostatic fan on my Uno 70SX is not switching on. I'm sure it WAS switching on when it hit the usual 90 degrees. However, since doing a clutch change it doesn't seem to be working. The engine goes up to 110 degrees and beyond and still no fan, at which point I switch the engine off to save any damage.

Wiring the fan direct to the battery shows it working fine, so the problem is NOT the fan.

Using a multi-meter at the fan wiring connector shows 12 - 14v getting through.

Using a multi-meter at the thermoswitch also shows 12 - 14v getting through.

Bridging the thermoswitch wiring connector does not make the fan come on.

A look at the Hayne circuit diagram shows a fairly simple circuit. Power comes from the the fusebox direct to the fan. The fan then connects to the thermoswitch, which then connects to earth.

So as I've got power going to both the fan and thermoswitch, how come the fan isn't coming on? Even more so when the thermo switch is bridged with a piece of wire? Any pointers????

 

[panda-sport]

Chas, have you disturbed an earth when removing/refitting the gearbox?

 

[Chas Uno]

Chas, have you disturbed an earth when removing/refitting the gearbox?

I was wondering that, but if I have how come I'm still getting an electrical reading at the terminals?

 

[jug]

checking for power is the first test, but you also need to test the fan's earth after the relay, and then test to see if the relay is getting a switch signal from the ecu at the correct temperature, and also test if the relay is switchig when it gets that signal. one of those tests will fail, thats your problem.

if there is no switch signal coming from the ecu then your coolant temp sensor is the most likely fault.

 

[maddogmorg]

have you checked for current before and after the thermo switch when cold? sounds odd either way.