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Discussion Starter #1
I have an 156 JTS where the cooling fan dosen't kick in. I've change the thermostat, coolant sensor and the fan resistor and still it won't turn on. The fan is working cause i can easily turn it on with wire directly from the battery. I can't see why it wouldn't turn on automatically, i can turn the fan on manually with obd cable and software, and here i can hear the clicking from the relays so they are working as well, it just won't turn on automatically. Any ideas?
 

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I have an 156 JTS where the cooling fan dosen't kick in. I've change the thermostat, coolant sensor and the fan resistor and still it won't turn on. The fan is working cause i can easily turn it on with wire directly from the battery. I can't see why it wouldn't turn on automatically, i can turn the fan on manually with obd cable and software, and here i can hear the clicking from the relays so they are working as well, it just won't turn on automatically. Any ideas?
There are 2 coolant sensors, 1 dedicated for the guage, another for the engine management.
The engine management one is responsible for switching the fan(s), via the ECU. This is also the temperature you read via the OBD.
Is this one working/correct ?
 

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There are 2 coolant sensors, 1 dedicated for the gauge, another for the engine management.
The engine management one is responsible for switching the fan(s), via the ECU. This is also the temperature you read via the OBD.
Is this one working/correct ?
Two sensors contained within one single sensor.
So to the user, there is only really one sensor (the one on the thermostat housing).
 

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I have an 156 JTS where the cooling fan dosen't kick in. I've change the thermostat, coolant sensor and the fan resistor and still it won't turn on. The fan is working cause i can easily turn it on with wire directly from the battery. I can't see why it wouldn't turn on automatically, i can turn the fan on manually with obd cable and software, and here i can hear the clicking from the relays so they are working as well, it just won't turn on automatically. Any ideas?
What temperature is it getting to?
Did you test the low speed and high speed fans via EOBD?
Low & High speed have separate relays.
 

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Discussion Starter #6
As long as the car is moving the temperature stays at 90 degrees, but whenever I'm stuck in traffic or such the temperature easily goes up and sometimes above 110 degrees.
Yeah, both fan speeds work.
 

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As long as the car is moving the temperature stays at 90 degrees, but whenever I'm stuck in traffic or such the temperature easily goes up and sometimes above 110 degrees.
Yeah, both fan speeds work.
On the guage or measured via OBD ? As said, those are not necessarily the same....

1st speed on the fan should also turn on when you switch on the aircon.....
2nd speed should come on if you disconnect temp sensor
 

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Discussion Starter #10
on most 156 models, they're co-located in the same housing in the thermostat, with separate electrical connections
There is only one sensor in the thermostat, but what you're saying is that it contains two sensors inside one?
 

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on most 156 models, they're co-located in the same housing in the thermostat, with separate electrical connections. can also be separate though
On the 156 it was only the very VERY early TS that had two separate sensors, the 2nd being in the end of the head. I'm sure it was only the Aluminium cam cover engines.
 

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There is only one sensor in the thermostat, but what you're saying is that it contains two sensors inside one?
Two sensor elements in one sensor housing.
One connector plug for both.
 

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Discussion Starter #13
Two sensor elements in one sensor housing.
One connector plug for both.
That might explain why the sensor has 4 pins, GND, VCC, temperature signal and the last pin might be the switch that activates when the temperature gets above a certain point.
 

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That might explain why the sensor has 4 pins, GND, VCC, temperature signal and the last pin might be the switch that activates when the temperature gets above a certain point.
Isn't a switch.
The switching is done by the engine ECU (which you say you've tested via diags).

The ECU switches the fan(s) by completing the earth side of the relay coil circuit.
The switch part of the relay(s) is on the earth side of the fan.
 

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That might explain why the sensor has 4 pins, GND, VCC, temperature signal and the last pin might be the switch that activates when the temperature gets above a certain point.
as also said by david, the 4 pins are for the 2 seperate (NTC) temp sensors, one for the guage, one for the ecu....
The ecu switches the fans according to the measured temp.
 

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Discussion Starter #16
Thanks, i'll try to reinstall the old sensor tomorrow, perhaps the new sensor i mounted along with the new thermostat is faulty..
 

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Thanks, i'll try to reinstall the old sensor tomorrow, perhaps the new sensor i mounted along with the new thermostat is faulty..
Genuine Alfa parts ?
 

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Discussion Starter #19
Piece of ****, still not working.. Guess i'll just cut the coolant hose in half and add a adapter with a coolant switch and make the fan come on that way, old school.
 

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Have you tried triggering the relays manually?
By earthing the earth side of the coil (the side the ECU switches).
I wouldn't be surprised if the relays (two relays remember) are faulty.

The problem with testing via diags is that it only pulses the fan, it doesn't run it for long.
 
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