Smart Fortwo 450 Cooling Fan

[Flossy]

Hi everyone, I have a 2003 Smart Fortwo 700cc, it recently overheated when my wife was driving it. It went to 4 blobs 100 degrees and lost some coolant. I have since found that the coolant tank was split and have replaced it. I have bled the system and all good now apart from the cooling fan doesn’t come on. I’ve read about the SAM but was wondering if there is also a sensor in the cooling system that could be faulty.

Thanks in advance for any assistance and advice.

[Thrumbleux]

Coolant fan rarely comes on and functioning gauge says temp sender is OK. Relax, enjoy the summer.

[Flossy]

Thanks, enjoy your summer too.

[heinkeljb]

The temperature sensor is clipped in to the thermostat and can be replaced if you think that is what you want to do. It is possible to put a variable resistor across the two wires that go to the temperature sensor and when adjusted to give the right resistance, the cooling fan will come on.

John

[Flossy]

Thanks for the info John. Do you know what temp the fan should come on? I thought it would come on before temp gauge went to 4 blobs 100 degrees. I had the temp sensor out when I bled the system after replacing coolant tank.

[Thrumbleux]

4 blobs is a rarity, intervention of the fan rarer still. About three times in my 12 years of 450 ownership.

[Flossy]

Thanks, just was a bit worried in case my car got roasted in the hot weather.

[Thrumbleux]

From memory, a little beyond 4 blobs and the fan will cut in. 4 blobs is rare though and if seen regularly it implies a cooling fault. Even in this current heat wave and driving hard, 3 blobs is the norm.

[tolsen]

I recall we discussed radiator fan cut in temperature not long ago but cannot find the thread. We even did some experiements connecting a variable resistance potentiometer in place of coolant temperature sensor to confirm exactly what temperature radiator fan would cut in.

[heinkeljb]

Found it over on the other forum:-

http://www.smartz.co.uk/showthread.php?22849-Front-cooling-fan/page3&highlight=temperature+sensor

John

[Thrumbleux]

Found it over on the other forum:-

http://www.smartz.co.uk/showthread.php?22849-Front-cooling-fan/page3&highlight=temperature+sensor

John

Post #39 is the relevant one re this thread - fan cut in point slightly above 4 blobs and 100degC.

John, did you ever get to the bottom of why no fan at 5 blobs and 120degC? Struggling to believe that 120degC was possible without the system being sealed tighter than a shark's arse at 1000 fathoms.

[heinkeljb]

No, but you have to remember that the Smarts temperature gauge only show "blobs" which cover 20 degrees a "blob£ so although my gauge showed 5 blobs, it might only have been just over 100 degrees as I stopped and allowed it to cool and added more water pretty soon after the flashing and beeping!

Testing the fan as per that thread, Fan works perfectly. I can only assume I have a very small leak somewhere and the water level got to a point where it allowed an air pocket to form. Which reminds me! Must go and check the water level again!!
John

[Flossy]

Thanks everyone for your help, it’s really good getting assistance and information.
Happy motoring all.