I have a 2003 Seicento with a cooling fan problem. The fan runs when wired direct, the 30A fuse behind the battery is OK but the fan does not come on when the water temp light come on - its just keeps getting hotter!! I understand the fan is operated by the water temp sensor via the ECU and a relay - but which relay? Has anyone had this problem before?

There was a recent post about this very issue. Not sure it was resolved.

If the Sei follows "normal" FIAT practice, then the earth side is switched, so, rather than suspect the relay, I'd test the - side of the fan contact (and, of course, the water temp sender).

if the warning light comes on, then surely the water temp. sender is good?

no, the fan is controlled by the ECU temperature sensor (one the inlet manifold, green i beleive on the MPI sei), the ECU and a relay.

the light is controlled by the gauge sender unit on the back of the head behind cylinder number 1. both systems are electrically independent of each other.

ignore the above ^^ tis wrong aside from the location of the ECU sensor

The fan and warning light are all controlled by the single temperature sensor found on the manifold (the green one arc mentions).

There are no other temperature sensors on the mpi non AC sei.

The ECU reads the sensor, and controls the light and fan.

If the light comes on and the fan doesn't there are 2 realys near the ECU on the right hand side of the engine bay. Try removing and replcing them.

Would input more but that should get you started...need sleep now

Yes - its now fixed - many thanks. The problem was a faulty relay ( part no 46520412 ) behind the ECU . There are two relays both with the same part no. The one nearest the bulkhead runs the cooling fan the other seems to immobilise the engine. So all is fine now - many thanks to all contributors!!

Are there two different types of green sender unit? - I got a replacement from Fiat but it seems to be incorrect. The one in the car looks more "delicate" and seems to have moulded plastic spigots surrounding the hex form on the sender unit, so cannot get a socket onto it. The housing it is fitted into appears to be plastic (nylon/glass?) and the sender unit I have from Fiat appears to have a much chunkier hex on it. The connector might be different also but not certain about that - can't make out the car version so well.

I think there are two different types of green sensors. I have been having trouble with a Schumacher model which is rather annoying. Fan kicks in then goes off then won't come back on again then obviously boils over

I'm doing the had gasket on it at the moment so I hope that is going to cure it

Thanks HF Turbo - that sounds annoying!

I guess the bottom line for me is:
Can I fit this:


Into this? (2003 Sei Sporting BTW):



If I cut the little square spigots away?

You should be able to unplug the wire from the sensor and slide a deep socket over the whole lot. That's how I did mine.

I just got rid of the **** T shaped pipe and fitted something like this (cant find the original link)

http://www.ebay.co.uk/itm/ELECTRIC-COOLING-FAN-THERMOSTAT-SWITCH-UNIVERSAL-KITCAR-RACE-RALLY/361344301109?_trksid=p2141725.c100338.m3726&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20141212152715%26meid%3D28d65442374248beb89f007f428919e9%26pid%3D100338%26rk%3D4%26rkt%3D30%26sd%3D130909180722

DRSIK said:

I just got rid of the **** T shaped pipe and fitted something like this (cant find the original link)

http://www.ebay.co.uk/itm/ELECTRIC-COOLING-FAN-THERMOSTAT-SWITCH-UNIVERSAL-KITCAR-RACE-RALLY/361344301109?_trksid=p2141725.c100338.m3726&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20141212152715%26meid%3D28d65442374248beb89f007f428919e9%26pid%3D100338%26rk%3D4%26rkt%3D30%26sd%3D130909180722

Click to expand...

There is no detail with regard to the switching current of the thermo-switch in the listing. I would recommend using with a relay.


The most common problem with "fan not working right" issues is the fan its self, leading to head gasket failure. The brush guides are plastic and can melt due to excessive heat, causing the brushes to not contact properly with intermittent operation. If the fuse has blown, this is a usual sign of the fan being the issue or a rare shorted wire.

Nod1 said:

Thanks HF Turbo - that sounds annoying!

I guess the bottom line for me is:
Can I fit this:
If I cut the little square spigots away?

Click to expand...

If the resistance range is the same,(most likely) then yes.

Cc1 how can I check the resistance on the fan?

I'm at ends teather at the moment

The fan comes in at 98 goes off ten back on again at 98 then off around 93. Then won't come back on!

I've changed the control relay

As the p0480 code came up

And it's still the same. I'm thinking as the motor is heating up do is the resistance so the relay is not switching the fan on at the right time. Just hope I haven't popped the gasket I've just replaced

Fan changed. All sorted

I am having the same problem with my sei temp sensor the little black locking pins shown in your photo stop my deep socket from sliding over the sensor, how did you get around this problem?

Magsy91 said:

I am having the same problem with my sei temp sensor the little black locking pins shown in your photo stop my deep socket from sliding over the sensor, how did you get around this problem?

Click to expand...

Use a spanner......

cc1 said:

Use a spanner......

Click to expand...

Sorted it a spanner won't get the sensor out you have to change the plastic housing too because the sensor should come complete......