Alfa Romeo 156 v6 2.5 when should the fans work - Alfa Romeo Forum
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Madness Alfa Romeo 156 v6 2.5 when should the fans work

Hello every one,

I am living in a place where the climate is hot near 30 degrees i have 2.5 v6 cf3, and it runs hot, i did some diagnostic and found the low speed fan start at 97c, is that something normal ? when should the first low speed start and the high speed start ? as far as my knowledge with bmw and other cars the low speed fan should start at 90c 91 or something and the high speed starts when it is over 100
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The low speed should start at approx. 92 C and the high speed should start at approx. 98C.
If the car has AC, the low speed will also start when the condenser needs cooling.
In the low speed a resistor is put in series with the fan to slow down the speed

To me it sounds like the low speed don't work in your car.
I assume your car has two fans right?
It has seperate circuit for the too fans (relays and resistors). Maybe both of your resistors have failed.
Have you used MES (MultiECUscan) to check if both fan speeds work?
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The low speed should start at approx. 92 C and the high speed should start at approx. 98C.
If the car has AC, the low speed will also start when the condenser needs cooling.
In the low speed a resistor is put in series with the fan to slow down the speed

To me it sounds like the low speed don't work in your car.
I assume your car has two fans right?
It has seperate circuit for the too fans (relays and resistors). Maybe both of your resistors have failed.
Have you used MES (MultiECUscan) to check if both fan speeds work?

Yaaah I did, both first speed and high speed works with the MES, i changed the engine temp sensor and it solved the issue for me, but when i drive the car aggressively the temp raises to 97 or even 100 and i have to slow down so the temp goes back to 92,


another thing, what i understood about the fans circuit that it is for high speed and low speed not for the first fan and the second fan,
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Ok, in that case then it could be the water pump that is worn and has a poor performance or if the radiator fins are corroded, restrict the airflow and don't cool enough
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"when i drive the car aggressively the temp raises to 97 or even 100 and i have to slow down so the temp goes back to 92" this sound to me like water pump.
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Ok, in that case then it could be the water pump that is worn and has a poor performance or if the radiator fins are corroded, restrict the airflow and don't cool enough
Before getting the pump changed, carefully check your radiator and the A/C condenser in front of it. If the fins are either damaged or corroded it will reduce airflow. Be especially careful if your car has the old copper radiator (painted black fins) as they turn to dust.

The 2.5 came with a plastic impellor which is prone to cracking and then slipping at high engine speeds but this has been known about for many years so it would be better to ensure it is not simply the radiator.
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My jts has the same properties. I connected ecu scan and watched as slow speed fan didnt come on until about 96oC. I thought it was the dial but the temp at which the fan came on corresponded with what the dial wad reading. It cools the car back down to 88-89 fairly quickly in my case but i dont know why its doing that. Ive been told thd fan on/temp particulars are set at the factory
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The rad and AC condenser are new, i think the water pump is faulty
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Guys i changed the water pump, and the same issue the first fan speed starts at 97.... is this normal ? i changed the engine water temp sensor and the same, could this be sensor for cold places ?
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Really now did you change water pump and cambelt?
When you use the A/C the fans work at speed 1. Did you try this?
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The 97C you mention is it the temperature reported by the Engine ECU?
Or it it a read out from the gauge?

Do the car still get warmer when you drive it hard?
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The 97C you mention is it the temperature reported by the Engine ECU?
Or it it a read out from the gauge?

Do the car still get warmer when you drive it hard?

Yes same issue with new pump, when it reaches 97 the slow speed kicks in, and this is not a gauge issue as i read that through MES, the first speed Kicks in at 97, could this be engine temp sensor issue ? that it sends the data to the ECU at 97 ? could be that ? And is this the normat behaviour for the CF3 2.5 v6 ? or is there is another engine temp sensor that it reads for example at 92 ? i need answers :'(
http://tinypic.com/r/8yx6yb/9


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I have checked the workshop manual and it is not mentioned anywhere at which temperature level the low speed and high speed should kick in.

As the 97C kick in for low speed you mention is reported by the Engine ECU it can't be a temperature sensor problem.
The temperature sender is just a NTC resistor (NTC stands for Negative Temperature Coefficient)
The resistor decreases with higher temperature and the Engine ECU just measure the resistance and use a look-up table to convert the resistance to a temperature.
A certain resistance corresponds to a certain temperature

So it seems the software in your Engine ECU is set to enable the low speed fan when the Engine ECU measure 97C cooling water temperature.

As the temperature sender includes a second NTC resistor for the gauge there can be a mismatch between the temperature reported by the Engine ECU and the temperature shown on the gauge.

I can try on my own 2.5 V6 to see at which temperature level the low speed kicks in.
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for most (all?) the later models, the temp. settings are:
low speed: 95 degr
high speed: 102 degr

as measured by the ecu.
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Originally Posted by Henrik_45 View Post
I have checked the workshop manual and it is not mentioned anywhere at which temperature level the low speed and high speed should kick in.

As the 97C kick in for low speed you mention is reported by the Engine ECU it can't be a temperature sensor problem.
The temperature sender is just a NTC resistor (NTC stands for Negative Temperature Coefficient)
The resistor decreases with higher temperature and the Engine ECU just measure the resistance and use a look-up table to convert the resistance to a temperature.
A certain resistance corresponds to a certain temperature

So it seems the software in your Engine ECU is set to enable the low speed fan when the Engine ECU measure 97C cooling water temperature.

As the temperature sender includes a second NTC resistor for the gauge there can be a mismatch between the temperature reported by the Engine ECU and the temperature shown on the gauge.

I can try on my own 2.5 V6 to see at which temperature level the low speed kicks in.
My Car is a CF3 version, has only 1 temp sensors that is sending to the ECU and the Gauge,also i changed it 3 times and same issue even the gauge i just changed it, the previous owner sold it for this issue, and i thought its something i can fix but i think this will kill me before i fix it
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Originally Posted by jwq View Post
for most (all?) the later models, the temp. settings are:
low speed: 95 degr
high speed: 102 degr

as measured by the ecu.

and how can i change that on the ECU maps ? did any one try to do that ? i have tried that in my previous e46 330 following the instructions on this website

Last edited by zewolf; 3 Weeks Ago at 21:15.
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Quote:
Originally Posted by jwq View Post
for most (all?) the later models, the temp. settings are:
low speed: 95 degr
high speed: 102 degr

as measured by the ecu.

and how can i change that on the ECU maps ? did any one try to do that ? i have tried that in my previous e46 330 following the instructions on this website
Perhaps you cant.
Theres been loads of input on this thread, from various models including 147 156 etc
Somebody said that the 147 dial is designed to operate so that it shows 90oC steady when the actual temp fluctuates between 85 and 95

If the operating temp is 90 then it makes no sense to turn the fan on at 91 or 92. It would wait till 95, then come on to cool the car down.

Maybe the manufacturer doesnt want us to see this fluctuation as its disconcerting to the driver but on some models the needle DOES indicate the change because...well....its an alfa and consistency is boring and not part of Italian flair and style. (No two alfas seem to be the same).

If the car does not steam or lose coolant and the fans seem to work and, in general ,there's no drama, then maybe its fine to leave it alone 👍
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Originally Posted by [email protected] View Post
Perhaps you cant.
Theres been loads of input on this thread, from various models including 147 156 etc
Somebody said that the 147 dial is designed to operate so that it shows 90oC steady when the actual temp fluctuates between 85 and 95

....
Yes, but that's only for later models with a CAN bus, like 147. The temp as measured by the ECU is processed and sent via CAN to the guage, see
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The 156 does not have a CAN bus (also not the V6)
As far as I know, the 156 ALWAYS has a seperate temp sensor for the gauge, independant of what is measured by the ECU.
However, the 2 temp senders are mounted in the same physical plug, with one electrical connector, on the thermostat housing making it look like 1 sensor.
The one going to ECU is a 2-wire connection, the one to the gauge is a singe wire (and ground).

see (K36 is combined temp sensor) :
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Last edited by jwq; 3 Weeks Ago at 06:58.
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actually, with the fan switch-on temps being 95 for low and 102 for high, the behaviour of your car sounds pretty normal ......

I guess if you really wanted, you could short-out/bridge the low speed resistors (O10 O12) for the fans, so they also run at high speed as soon as low speed comes on, so at 95.
Or as compromise, only short one of the resistors....
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Yup....and it all points to the fact that all is well.p
The SOT is 90oC and thermostatic control is a negative feedback system. So it should fluctuate between 85-95, when in stop/start traffic etc. If its steady at 90 in normal running it kinda seems that yours (and mine) are running normally and within accaptable parameters
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Guys i do not understand how this is normal, if this is normal that the car run on 97, why the gauge shows it is not normal, here is a link of the gauge running on 97 Image - TinyPic - Free Image Hosting, Photo Sharing & Video Hosting i dont know how to attach pics here
but anyways, yah my car cf3 and has ony 1 sensor with 4 pins that is sending the data to the ecu and the gauge, what i need to understand what is missing here why the gauge shows the temp is high while it is normal, as i believe cf3 cars has canbus so this problem should not happen,
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Quote:
Originally Posted by zewolf View Post
Guys i do not understand how this is normal, if this is normal that the car run on 97, why the gauge shows it is not normal, here is a link of the gauge running on 97 Image - TinyPic - Free Image Hosting, Photo Sharing & Video Hosting i dont know how to attach pics here
but anyways, yah my car cf3 and has ony 1 sensor with 4 pins that is sending the data to the ecu and the gauge, what i need to understand what is missing here why the gauge shows the temp is high while it is normal, as i believe cf3 cars has canbus so this problem should not happen,
No, 156 CF3 cars do NOT have CAN bus, and the temp gauge is analog, not stepper controlled.... As said, your car uses 2 seperate sensors built into the same case, one for the gauge, one for the engine ECU, which is also confirmed by your own statement that the sensor has a connection with 4 pins .
This means that in theory what the gauge displays and what MES indicates (the ecu measurement) can differ, as they use seperate sensors. Usually the temp as measured by the ecu is more accurate, this is also used to controll the fan switch-on/off.

156's are known to often have less accurate temp.gauges, though they do react immediately to all temp changes, contrary to the more modern cars with gauges controlled via can bus/ecu (for example 147, giulietta, mito etc.), which reflect what the ecu measures, but are damped as mentioned before.
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