Hello guys,

So, since most stuff here seems to be about seis and I have a cinq, I'm going to ask a few questions and try to solve this issue or at least "fix for now".

The temp gauge was taking a long long time to hit the 90ºC, so I flushed the system (so much orange crap and water), the thermo was broken open, so it wouldn't heat and got replaced by a new one, and the temp sender (red on the engine block), got replaced also.

So, now the car hits around 90ºC and the thermostat opens and stays around there, everything fine by now. The issue is, I do believe the head gasket is bad, so that's why it get hotter when its idling and I'm trying to know when the radiator fan kicks in. I disconnected the radiator temp sender wiring (the conector to the sender unit) but it didn't work, so I bypassed it and the fan is always on, even when the car is off I believe so it's not a good solution :bang:. Also, sometimes, before hitting the 130ºC second mark, sometimes the fan decides to start... the thing is, I'm afraid to test without knowing if it is normal or not to start at that temperature (a bit less)...

I need to know if there is a way to bypass the fan, so it always stays on, or to test the temp sensor in the radiator to start the fan (Ohms expected etc)


Thanks so much!

Hey Kunkunlol,

I've done this a few times on a few FIATs; there are various different solutions.

At the simplest level (on a Mk1 Croma);
I replaced the radiator thermal-switch for a lower-temp switching one; from a Lancia Thema turbo (if I remember correctly)

At the most 'advanced' solution on something else;
I paralleled the thermal-switch lines from the loom to a normally-open relay pair; and ran a switched feed to the relay from an ignition-switched (+) line from the fag-lighter socket.

In this way; the system maintained autonomous operation, whilst I gained additional control (when I wanted) but which was ultimately overridden by the car when turned off.
-Radiator fan(s) can pull 30A; you don't really want that running with the car off.

I can't offer you an impedance reference for a known-working thermal-switch.
I can suggest that you change the part; there's NO WAY you should be seeing 130 on the temp gauge; if you don't have head-gasket problems now; you will shortly!

What condition is the radiator in? Could just be old, blocked up and inefficient? I had this cause overheating on a hot summers day.

Healthy cooling system should not need a fan overide switch!


I got a new Seicento radiator recently for £18 delivered, worth a try!

If the gasket was blown you'd have either mayonaise on the oil cap and possibly wildly swinging temp gauge when hot gasses surround the engine temp sensor. Also steam engine sights and smells from the exhaust are a give-away!