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Discussion Starter #1
Hi all,

I have a Alfa Romeo 2.5 V6 - very young, only 63k miles.

The internal/cabin fan is not working at all. The fan, when selected on any setting (1-4) does not respond nor work at all.

So far I have checked;

- Battery fuses and bonnet relays (all working)
- Driver side relays (all working)
- Relays & Fuses ontop of blower fan (all working)
- Blower fan (working, tested via battery)
- Blower fan solonoid (working, tested via multimeter)


I am completely lost as to what the problem could be..

Some are suggesting it's the actual fan dial that's causing the problem but all three dials have the back-light working and when you click the A/C to turn it on you can hear a click & gas moving, so the A/C compressor is working and it appears the dial is working fine.

The unique thing about my situation is the fan is not working on ANY setting, not even 4.

Cheers all!
 

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Discussion Starter #3 (Edited)
Thanks jwq for that! It appears to be the issue..

http://i.imgur.com/eDQW06N.png - you say the electric fan motor speed variator is the problem so it appears that I would just need to replace the entire HVAC panel, it would be easier to do that than just to replace that one bit? I'm having a hard time sourcing even the HVAC panel that I require, I highly doubt I would be able to source the electric fan motor speed variator just by itself, it looks looks complex to replace just that one bit itself. I'm in Sydney by the way.

Cheers

EDIT:

Appears the electric fan motor speed variator is actually the solenoid/resistor(??) in which case I have already confirmed the solenoid/resister and fan are both functional.
 

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The Speed variator is an electronic part and not just a solonoid/resistor.

The speed variator is placed in the ground side of the fan motor and consist of a MOSFET output stage that make a a pulse width regulated output voltage and by this means regulate the voltage across the fan motor.
The speed variator is conctrolled by pulse width modulated square wave signal coming from the ECU for the climate control.

I would like JWQ say that the problem is most likely caused by the speed variator and not by the ECU.
 

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Internal/cabin fan is not working

The Speed variator is an electronic part and not just a solonoid/resistor.

The speed variator is placed in the ground side of the fan motor and consist of a MOSFET output stage that make a a pulse width regulated output voltage and by this means regulate the voltage across the fan motor.
The speed variator is conctrolled by pulse width modulated square wave signal coming from the ECU for the climate control.

I would like JWQ say that the problem is most likely caused by the speed variator and not by the ECU.
Hello, I am an Alfa 156 owner, it is from 1998. The climate fan has stopped working. The fan doesn't work on any of the 4 settings. I have revised a lot of posts, diagrams and also have made some testing.

If I connect the fan directly to the battery it works, so it can't be the problem. Now I want to know if the problem is the speed variator, but I don't know how to test it. Please, can somebody tell me how to check if the variator is failing using the tester? I've made some checks in the related cable connectors, and it seems Voltage is arriving there properly, although I am not sure that the values are adequate.

On one of those checks I was testing the 3rd pin of the connector B of the speed variator (M70), and as I was changing the fan speed on the control unit through 1-4 the Voltage showed different measurements. But I don't fully understand the diagram or all the tester checks that I can do and know how to interpret them. I think it can be due to the speed variator unit, or some cable or connector.

Can somebody help me and explain where do I have to put the tester probes to check that the speed variator and the two connector arriving to it are working?

Help you a lot, it is really hot here and in two weeks I have a long travel through the center of Spain so it is really iimportant to get it fixed :hehe:
 

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I assume that you have had a look at the wiring diagram.

http://www.alfaowner.com/Forum/alfa-147-156-andamp-gt/1014209-help-with-my-156-sportwagon-pleeeeease.html#post15219465

To debug you need a voltmeter and measure voltages in the curcuit

Measure the voltage at the motor N85 (Pin A). If you measure 12V here the wiring from battery is ok. If you don't measure any voltage the wiring towards the battery is broken.

Measure the voltage at the motor N85 (Pin B). If you measure 12 V here the motor don't get any ground connection through the speed regulator M72. If you measure 0V the motor is broken. To test the circuit you can try to ground this pin with a wire. If the circuit is ok the fan should run a full speed when you ground (make sure it is Pin B you ground and not pin A else you will blow the 40A fuse)

Measure the voltage at the speed regulator (Pin A). If you measure 12 V here the motor don't get any ground connection through the speed regulator M72. If you measure 0V and measured 12 V at Pin B on the motor the wire is broken. If the speed regulator is working you should measure a variable voltage that will vary with the speed step you set on the dial. Lower (closer to 0V) at step 4.

Measure the voltage at the speed regulator pin B pin 1. If you measure anything here above approx. 0.5V the wire or ground connection is broken.
 

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I assume that you have had a look at the wiring diagram.

http://www.alfaowner.com/Forum/alfa...y-156-sportwagon-pleeeeease.html#post15219465

To debug you need a voltmeter and measure voltages in the curcuit

Measure the voltage at the motor N85 (Pin A). If you measure 12V here the wiring from battery is ok. If you don't measure any voltage the wiring towards the battery is broken.

Measure the voltage at the motor N85 (Pin B). If you measure 12 V here the motor don't get any ground connection through the speed regulator M72. If you measure 0V the motor is broken. To test the circuit you can try to ground this pin with a wire. If the circuit is ok the fan should run a full speed when you ground (make sure it is Pin B you ground and not pin A else you will blow the 40A fuse)

Measure the voltage at the speed regulator (Pin A). If you measure 12 V here the motor don't get any ground connection through the speed regulator M72. If you measure 0V and measured 12 V at Pin B on the motor the wire is broken. If the speed regulator is working you should measure a variable voltage that will vary with the speed step you set on the dial. Lower (closer to 0V) at step 4.

Measure the voltage at the speed regulator pin B pin 1. If you measure anything here above approx. 0.5V the wire or ground connection is broken.
Thanks a lot for answering Henrik_45 :wink_org:

Yes, I've been reading a lot on this issue. I have downloaded the eLearning tool, revised the diagrams, the explanation of how it works and have researched a lot
about this issue. Yesterday I even found a post by a polish user who explains how to fix the speed variator, and maybe I will do that, but first I want to be shure
that my speed variator is damaged:

Naprwa opornicy (rezystora) nawiewu klimatyzacji Alfa Romeo 156 TS

Because of this I am fond of knowing more about the electronics of the car and being able to fix this problem myself. Even so I have some doubts about the checks you explain:

1) To do these checks, do I have to turn the fan dial on any particular speed?
2) When you say measure the voltage at some Pin, I have to put the positive voltmeter probe at that Pin and where do I have to put the negative voltmeter probe? To some other Pin, to the car chassis that is grounded or where?
3) To do these checks, all the parts (fan N85 and variator M72) have to be mounted or unmounted? And related to that, I take the measures on the connector of the cable
or where?
4) Among all the checks you explain, the one that can prove if the speed variator is working or not is that one "If the speed regulator is working you should measure a variable voltage that will vary with the speed step you set on the dial. Lower (closer to 0V) at step 4. ", am I right?

The explanation of eLearning about the M72 contains that:
The distribution actuator N80 is controlled by the control unit M70 from pin 16 of connector A, receiving a supply for controlling the potentiometer from pin 2 of connector A and sending a feedback signal to pin 9 of connector B.

The electronic governor M72 operates the fan at different speeds: it receives an input signal from the control unit (from pin 3 of connector B) and transforms it into a variable voltage signal that controls the fan. This voltage control is also stabilized, i.e. it is independent of the battery voltage variations. The governor supply is controlled by the ignition (INT/A) from fuse B10 up to 2/99 or fuse F6 of the additional fuse box B98B from 2/99, is connected to earth and also sends the temperature control signal to pin 4 of connector A of M70 .


As seen in the diagram, the speed variator (M72) has Pins A, B, and Pins 3, 2 and 1 (G, A, C are for cable color).
5) Pin A comes from N85, where does Pin B goes? To earth I suppose, right?
6) Pin 3 receives an input signal from the control unit. I think it is a variable voltage depending on the selected speed. But what are Pins 2 and 1 for? I can not find it anywhere.

7) And finally, is there any way to know if the speed variator is ok or not, having extracted it from the car, using a voltmeter and an electricity generator?

Excuse for the lack of electronic knowledge and thanks for the help! :vs_smile: It is really appreciated
 

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Answer to your questions.

1. It is only the voltage on Pin A of M72 that will vary depending on the dial setting. The other voltages should be stable.
2. When you measure voltages put the negative terminal of the voltmeter to chassis of the car and use the positive terminal of the voltmeter to measyre the voltage in the different connections.
3. M72 and N85 needs to be mounted and connected. To measure the voltage see if you somehow can get connection to the connector springs in the connectors.
4. Yes the voltage at the side of N85 that is grounded through M72 should be variable and closes to 0V when the dial is set to 4.
5. Pin B of speed variator M72 goes to ground (Chassis)
6. Pin 1 is 12V that is present when ignition is turned on.
7. Only if it is short circuit not if the MOSFETs in the speedvariator is broken as open circuit

If you have the right diagnostic interface you should also be able to test the fan speeds with MultiEcuScan.
To have the right function will of course require that the speed variator is functional.
 

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Answer to your questions.

1. It is only the voltage on Pin A of M72 that will vary depending on the dial setting. The other voltages should be stable.
2. When you measure voltages put the negative terminal of the voltmeter to chassis of the car and use the positive terminal of the voltmeter to measyre the voltage in the different connections.
3. M72 and N85 needs to be mounted and connected. To measure the voltage see if you somehow can get connection to the connector springs in the connectors.
4. Yes the voltage at the side of N85 that is grounded through M72 should be variable and closes to 0V when the dial is set to 4.
5. Pin B of speed variator M72 goes to ground (Chassis)
6. Pin 1 is 12V that is present when ignition is turned on.
7. Only if it is short circuit not if the MOSFETs in the speedvariator is broken as open circuit

If you have the right diagnostic interface you should also be able to test the fan speeds with MultiEcuScan.
To have the right function will of course require that the speed variator is functional.
Thank you a lot for your help, I will check the car this afternoon.

1) I think it will be difficult or impossible to take measures with the voltmeter if the n85 and M72 are mounted, but I will try anyway. Could you tell me how?
I will also apply spray for electrical connectors on these connectors and Pins.

So, I know that for connector A of M72, Pin A comes from Pin B of N85, and that Pin B goes to ground.
2) And that for connector B of M72, as you say Pin 1 is 12V that is present when ignition is turned on. It is curious, why is it necessary
for the M72 to know whether the ignition is turned on?
3) For the rest of Pins of connector B of M72, Pin 3 receives an input signal from the control unit (from pin 3 of connector B) and transforms it into a variable voltage signal that controls the fan (stated in eLearn guide), right?
4) And what are for Pin 2?
5) And Pin 4?
Because the connector has 3 wires, but there are 4 Pins in total in connector B.

6) I've taken some pictures from this part of the car, and I see a red connector not connected to anywhere. Do you know what it is for?

Thank you a lot :thumbu p:
 

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If you pull out the black connector (M72) with the large orange and black wire and short circuit the wires then the heater fan should run at full speed if the wiring and fan motor is ok. (Be aware the current is quite high)
If the test above is passed the problem is probably caused by the speed regulator.

If the B connector on M72 has 4 pins, the fourth pin is not used to anything.
To my knowledge pin 2 is a feedback signal to the Climate Control ECU.

The functionality of the speed regulator is the following:
Depending on the signal (pin 3) from the Climate Control ECU, the speed regulator will have a variable resistance between pin A and Pin B and by this means the current through heater fan motor is variable.
To describe the functionality of the regulator in detail will require you have some electronic knowledge as it is done with a pulse width modulation circuit.
 

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If you pull out the black connector (M72) with the large orange and black wire and short circuit the wires then the heater fan should run at full speed if the wiring and fan motor is ok. (Be aware the current is quite high)
If the test above is passed the problem is probably caused by the speed regulator.

If the B connector on M72 has 4 pins, the fourth pin is not used to anything.
To my knowledge pin 2 is a feedback signal to the Climate Control ECU.

The functionality of the speed regulator is the following:
Depending on the signal (pin 3) from the Climate Control ECU, the speed regulator will have a variable resistance between pin A and Pin B and by this means the current through heater fan motor is variable.
To describe the functionality of the regulator in detail will require you have some electronic knowledge as it is done with a pulse width modulation circuit.
Thank you for your great the help.

1)As you say, I pulled out the M72 and short circuited the orange and black wires and then the fan did run at full speed :beer:
It run even without key in the car. So it is completely tested that the fan is working and that those wires are in good state.
Although I must admit that strangely, the air seems to come all out from under the glove compartment and does not seem to
come out by the corresponding airvent and they were opened. What can it be? Video: https://streamable.com/43sk0

Well, it can only be the M72 and/or the connector B with 3 wires that are causing the problem of the fan not working.

On the connector B I did some measures with the voltmeters and I get that:
-Pin 1(goes to orange wire) I got 12 V, even if the engine is not started
-Pin 2(goes to blue wire) I got 0V (it makes sense if as you say pin 2 is a feedback signal to the Climate Control ECU)
-Pin 3(goes to yellow wire) it is variable depending on the selected fan speed, the measures were:
Pos 0: 0V
Pos Auto: 11,22 Volts
Pos 1: 4,88 Volts
Pos 2: 5,11 Volts
Pos 3: 6,44 Volts
Pos 4: 11,22 Volts

It seems the connector B is working good, isn't right? So I will open the M72 and check for any failure with the
help of a friend who is electrician. We will test the fan and the speed regulator making the connections as they
are in the car and using some electric generators, one for the fan and one for the speed regulator.

2)Do you know how many amps needs the fan? And how many amps needs the connector on Pin1 and Pin 3?
I know the Volts to apply but not how many Amps. And if you can tell me more detailed description of
how it works it will be of great help

3)On the other hand, do you know what the red connector in the picture is for?

4)I do not know if it has anything to do with it or not, but as soon as I put the key in the MAR position, I start to hear a frequent sound of CLA CLA CLA very annoying. It seems that the origin is in the area of the hood through which the outside air must enter. Do you know what might be due? I show it in these videos: https://streamable.com/uhq59 https://streamable.com/xaunq

5)Does the fan look good on the photos?

Thanks for all
 

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With the tests and measurements you have done I would say it is the speed regulator that is broken.

The bearing seems a little rusty but if the fan runs freely I don't think it is a problem.

I don't know what the noise you are hearing might be.
Can you hear if it is comming from the engine bay or or from the heater system?
It could be the climate control that is trying to self calibrate.
 

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With the tests and measurements you have done I would say it is the speed regulator that is broken.

The bearing seems a little rusty but if the fan runs freely I don't think it is a problem.

I don't know what the noise you are hearing might be.
Can you hear if it is comming from the engine bay or or from the heater system?
It could be the climate control that is trying to self calibrate.
Thanks again Henrik :thumbu p:,

Later on this week I will make the final tests on the speed regulator and then repair it if it is possible or order the replacement car part.

1) About this red connector that isn't connected to any part, I don't know what it is and that worries me. Do you or someone
point me what it is for? Please. Maybe it has to be connected to some place... I don't know. I reattach the picture

2) For this CLA CLA sounds, it sounds when I put the car and the electronics are started (lights, radio... etc.)
I think it can be an air flap that has a problem, it may be blocked or having some problem. It is heard from inside the vehicle.
From the outside, it is a bit more loud, and it comes from under the plastic that is in the bottom of the windscreen, in its center
close to the central wiper, as I show in the video of the previous post.

I've been reading about similar cases in forums and they recommend to disconnect the battery for some minutes in order to
reinitialise the air flaps of the climate system. I will try this.

Thank you a lot,
Sergio
 

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