Technical radiator fan switching on early

[dowdow]

HI there.i have a mk2 fiat uno 1000cc carb engine.the problem is that the switch cuts in very erlier than other unos I know..it will start working at about 40dec ..where it should start at 90deg..i changed the radiator fan switch.but it still the same..I changed the temperature sender..but it is still the same!:bang: any help pls?! thanks:worship:

 

[Ucof]

Possibly an ECU reset?
Was the temp sender replaced with a new one?

Would anyone else agree with that?

 

[lewey]

Possibly an ECU reset?
Was the temp sender replaced with a new one?

Would anyone else agree with that?

No. Carb car, so no ECU. ECU does not control fan on any Uno anyway.

If the rad switch has been replaced, it is very likely that the fan is turning on at the correct temperature. It is more likely that the gauge is reading low. As you have replaced the sender for the gauge also, I would suspect the gauge.

When the fan kicks in, can you comfortably hold the top coolant hose near the rad? At an actual 40 degrees, you could.

 

[dzogi]

Don't mind me being dumb, but does switch=thermostat?

 

[lewey]

No. "Thermostat" being valve on side of engine to allow flow of coolant through radiator. "Switch" being the fan or radiator switch. Electro-mechanical switch that turns on electric radiator fan when it senses 95 degrees in the radiator coolant.

 

[dzogi]

I thought I heard someone saying that fan is operated by so called "thermostat", the part which measures the heat. It's supposed to be adjustable, so you can set it to "turn on" at 3 different positions. Maybe his is set on "low"? (just a thought trying to help )

 

[lewey]

I thought I heard someone saying that fan is operated by so called "thermostat", the part which measures the heat. It's supposed to be adjustable, so you can set it to "turn on" at 3 different positions. Maybe his is set on "low"? (just a thought trying to help )

I haven't heard of that system before. Perhaps a link to this info would be good? I know you're trying to help, I don't mean to offend by answering concisely

 

[Chas Uno]

I've seen after-market electric fan kits that come with adjustable fan thermo-switches (that switch the fan on and off at temperatures determined by the user). However, the standard Uno electric fan only operates via the thermo-switch on the radiator which is non adjustable.

I agree with Lewey in that it may well be a faulty gauge giving an incorrect reading.

 

[Ucof]

That was my back-up option



Silly me Lewey

 

[dowdow]

hi there..the fan from my experience is working to early..but not as the temperature guage is working bad..becouse after about 5 minutes drive..the fan starts..where on any other "normal" fiat uno fire it took about 15 or more minutes!

 

[lewey]

OK. If you have a genuine 95 degrees coolant in the rad, which it sounds like you have as it is a new switch, you have an engine overheating issue. This is most likely your water pump. The gauge must be reading too low if we believe the coolant is 95 degrees. This could be because the gauge is broken as we guessed before or because there is an air pocket surrounding the sensor in the head. This would make the gauge read low.

I really do not think this is an electrical issue. It is a mechanical engine issue.

Did you fit a new, not second hand switch? How hot is it where you are at the moment?

 

[Ucof]

Have you bled the coolant system at all?

Can you try holding the big pipe out of the radiator when the fan is spinning please? If it is too hot to hold, then the fan is kicking it at the right temperature, then like Lewey says, it is likely to be a bubble of air at the temp sender stopping it from showing the right temperature

 

[dowdow]

hi..thanks for your help!. the senser i have fitted is new..a 90dec switch..the tempereture here is about 27dec! hot eh?! I try to check the hose pipes when the fan is on..but if I am not mistaken..they were cold! both of them! the fan starts after only a few minutes! even if there is a pump failure.. i am in doubt if it will be 90dec near the fan switch!..I will keep you updated! help!

 

[lewey]

Total mystery! The fan electrics are so simple, it just has to the switch since that is the only thing stopping the fan being on all the time. On the bright side, it seems your engine cooling is OK and you can probably ignore what I was saying about the water pump, etc.

 

[lewey]

P.S. 12dec here!

 

[dowdow]

HII ! I wish the weather here is like yours weahter! here is too ho! regarding the fiat uno..if the pump is broken or the system is not bleed good..it will overheat to the point that it will lock! especially with this weather! I will try to replace the thermostat..it is not expensive...

 

[lewey]

You said the pipes going into the radiator were cold, but the fan is on. This is not possible if the electrical fan switch in the radiator is working properly. End of story.

 

[Chas Uno]

You said the pipes going into the radiator were cold, but the fan is on. This is not possible if the electrical fan switch in the radiator is working properly. End of story.

:yeahthat:

The electric fan circuit has a positive 12v supply going to the fan, then the circuit continues to the fan thermo-switch, which is then earthed to a point on the car body (under the battery tray). The switch requires the coolant temperature to reach a set temperature point to heat it up before it will allow current to pass through it, earthing the power feed and allowing current to flow through the electric fan motor thereby operating it.

If the pipes to and from the radiator/ thermostat are cold and/ or the radiator itself is cold and the fan still operates then there can only be two possible faults. One, the radiator fan switch is still faulty or two, there is a fault in the fan wiring that is allowing the 12v feed from the fan motor to earth itself prior to reaching the thermo-switch. There can be no other possible reason for the fan to come on at such a low temperature.

You can check the (very simple) wiring diagram showing the fan circuit on page 317 of the old style Uno Haynes workshop manual.

 

[dowdow]

hi..the only poossible problem I was thinking was that it is an electrical fault..I will try to make a simple wiring diagram..earth with the minus on the battery ,and pfeed to the plus of the battery..and of course in beetewwen teh earth i will put the switch..hope it will work!

 

[dowdow]

HI there..I had some time to check the uno..I made a new wiring circuit...plus of the fan goes to battery positive..earth of the fan goes to the switch ,and another wire from the switch to the negative of the battery..it changed nothing !.so this is not an electrical fault.unless it is a faulty switch,which I had replaced last week with a new one. next time I will remove the water pump and inspect it.and the thermostat. because when ta fan starts..the radiator and hose pipe near the radiator were hot..very hot.but the engone block..near the water temperature senser where not that hot.not cold.but you can touch it without going burnt! hope this will help!