Technical ignition off but fan on - always

[moizeau]

A friend has a 2002 1.2 Doblo.A/C
The low speed fan stays on, without keys, flattening the battery. A local mech said he'd sorted it by changing the temp sensor and fan resistor. All was good for 3 days when the battery still flattened. The car went to fiat who said they couldn't find a problem.
The car then came to me. I found that the temp sensor hasn't been changed( still factory jube clip with QA mark on it)However the temp gauge works fine, so I don't think this is the problem. The resistor may or may not have been changed(There was a screw missing but I beleive this only slows the motor down, so this shouldn't be the problem) When I disconnected the battery I heard a click and traced it to the low speed relay (no key in) When I checked the connections with the relay removed the signal feed to the relay is powered all the time. Thus, I've taken F6 out which does the low speed and checked that the normal fan still comes on so the engine won't overheat. This has cured the flat battery but I'd like to know what feeds the relay. I have read that it is something to do with the A/C. I'd like to cure the problem properly and refit the fuse. Any suggestions gratefully accepted.
Thanks

 

[moizeau]

Anyone please
Any suggestion

Thanks

 

[T14086]

you say the relay is constantly on, it is switched by the ECU.

 

[moizeau]

Thanks for the response
That's the problem. I don't know what switches the relay. Is the ECU or the A/C?
There are know new fault codes after I cleared them and everything else works great!
Cheers again

 

[moizeau]

What tells the ECU to switch the relay? There must be another sensor somewhere?

 

[T14086]

it will be the ECU but what is making the ECU trigger the fan is the question? If the coolant sensor is ok (as you say) then the ECU could be faulty or the wiring between ECU and relay shorted to earth. Quickest way to tell is when the fan is staying on and key is out of ignition disconnect the ECU, if fan stays on its wiring if not it's ECU/coolant sensor.