Fiat Croma heater will turn on but will not blow any air.l

Looks like you have a fault with the heater flap actuators . This explains and shows the set up . The link does not allow copying

194001899 - AIR CONDITIONING CASING AND COMPONENTS
AIR CONDITIONING CASING
The air conditioning casing, in other words the plastic structure fastened to the dashboard supporting crossmember, is the same on both the manual and the automatic version.
The difference between the manual and automatic versions (as far as the air conditioning casing is concerned) lies exclusively in the type of mixture, distribution and recirculation flap movement actuators.
COMPONENTS
The components for the type of system are listed in the table below.
Components
MANUAL climate control
AUTOMATIC climate control
DC actuators
X
X
Stepping actuators
X
Mixed air temperature sensors
X
Heater radiator
X
X
Evaporator
X
X
Expansion valve
X
X
Fan
X
X
Climate control node
X
X
Compressor
X
X
Condenser
X
X
Linear sensor
X
X
Outside air temperature sensor
X
Passenger compartment air temperature sensor
X
Solar sensor
X
Pollen filter
X
X
Drier filter
X
X
Air quality sensor (AQS)
X
Description of the components
The location of the main components is illustrated in the diagram below

1 - outside air intake
2 - recirculation air intake
3 - electric fan
4 - evaporator
5 - heater
6 - FLOOR air outlets
7 - side VENT air outlets
8 - centre VENT air outlets
9 - DEF air outlets
10 - rear VENT air outlet
11 - rear FLOOR air outlets
12 - fan electronic control (automatic climate control)
13 - resistive divider (manual climate control)
The location of the sensors and the actuators is illustrated in the diagram below.

1 - recirculation actuator
2 - right side distribution actuator
3 - left side distribution actuator (on automatic version only)
4 - left side mixing actuator
5 - right side distribution actuator (on automatic version only)
6 - left side Vent treated air sensor (on automatic version only)
7 - left side Floor treated air sensor (on automatic version only)
8 - right side Floor treated air sensor (on automatic version only)
9 - right side Vent treated air sensor (on automatic version only)
ACTUATORS
The movement of the flaps inside the climate control casing, in other words the air mixing, distribution and recirculation flaps, takes place thanks to electro-mechanical actuators controlled by the NCL.
On the manual climate control versions, the actuators contain a motor with a 12 volt power supply that controls the rotary movement of a drive pin, by means of linkage, acting directly on the flaps. On the mixing and distribution actuators a potentiometer determines the effective position of the flap and acts as feedback for the control unit. The recirculation actuator does not require a potentiometer.
The actuator for the manual version is illustrated in the diagram below.

On the automatic climate control version the 12 Volt actuators for the distribution and the mixing are replaced by stepping motors which, by means of linkage or gears, control the rotary movement of a drive pin that acts directly on the flaps. In this case the positioning takes place by counting the number of steps required to reach the position. The recirculation has the same actuator as the manual version.
The stepping motor for the automatic version is illustrated in the diagram below.

Air distribution actuator
The air distribution actuator operates the rotation of the distribution flaps by moving a cam that acts on an idler linkage for each flap.
On the manual climate control version it receives a 12 volt power supply and, by reversing the polarity, it can be made to rotate either clockwise or anti-clockwise. A potentiometer measures the effective position and acts as feedback for the control unit, checking the complete travel between the end of travel positions. It is fitted on the climate control casing on the right hand side.
On the automatic climate control version the actuator is replaced by a stepping motor. As the automatic version is the dual zone type, the mechanism that moves the flaps is on both the left and right sides of the climate control system. The movement of the flaps for the left and right sides is completely independent of one another. The positioning takes place by counting the number of steps required to reach the position.
Air mixing acuator
This actuator activates the rotation of the air mixing flaps by means of linkage. It is fitted on the climate control casing on the pasenger side.
On the manual climate control version it receives a 12 volt power supply and, by reversing the polarity, it can be made to rotate either clockwise or anti-clockwise. A potentiometer measures the effective position and acts as feedback for the control unit, checking the complete travel between the end of travel positions.
It is fitted on the climate control casing on the left side.
On the automatic climate control version the actuator is replaced by a stepping motor. As the automatic version is the dual zone type, the mechanism that moves the flaps is on both the left and right sides of the climate control system. The movement of the flaps for the left and right sides is completely independent of one another. The positioning takes place by counting the number of steps required to reach the position.

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Recirculation actuator
The actuator manages the rotation of the flap in two extreme positions: dynamic (outside) air and recirculation, without intermediate positions.
It is fitted in the area of the dynamic air intake
It receives a 12 volt power supply and, by reversing the polarity, it can be made to rotate either clockwise or anti-clockwise.
CLIMATE CONTROL SENSORS
Mixed air temperature sensors
There are four temperature sensors on the automatic climate control casing that provide the climate control system control unit with a signal relating to the temperature of the air coming out of the vents. Two sensors are located by the FLOOR outlets and two others by the dashboard side vent outlets.
The sensors are the NTC type and feature a resistance of 10000 Ohm +/- 3% at a temperature of 25 °C
The temperature sensor is illustrated in the diagram below.

Solar sensor
The solar sensor is located on the top part of the dashboard at the base of the windscreen.
Its task is to transform the light signals (lux or kcal/m²h) into a corresponding linear electrical signal to supply a value proportional to the thermal energy introduced into the passenger compartment through the windscreen through the effect of the sun''s rays.
This sensor is only fitted on the automatic climate control version.
The sensor is a special type of diode (photodiode) which can alter its conduction depending on the quantity of light coming into contact with it.
If the climate control system control unit (NCL) is managing the system in AUTO mode, it uses this signal and alters the air temperature and distribution parameters to maintain the temperature requested by the user.

A - Solar sensor
B - Diagram showing operation of solar sensor
1 - Left solar sensor
2 - Temperature sensor (N.C.)
3 - Right solar sensor
4 - Earth
Pollution sensor (aqs)
The AQS sensor is an electronic device that is designed to send an opening/closing signal signal to the distributor unit recirculation flap when the outside air pollution index exceeds pre-set harmful levels to prevent polluted air from being introduced into the passenger compartment.
It is installed in the distributor unit outside air intake.
It is possible, through the use of a special sensitive element, to detect the presence, in the air surrounding the vehicle, of oxidizing pollutant particles (e.g. CO) or reducing agents (NOx).
The sensitivity of the system is improved by the potential danger of the pollutant gases according to the M.A.K. index (Maximal Concentration of Harmful Substances at Work Over 8 Hours).
The sensitive element is heated and regulated at a constant temperature of 300°C to supply the same performance in an ambient temperature range of between -40 and +85°C. It is not affected by the speed or the temperature of the air passing through it.
The AQS sensor is illustrated in the diagram below.

Pin out (3-way connector)
PIN
FUNCTION
1
Power supply +15 (INT)
2
Reference earth from NCL
3
PWM signal for NCL

The sensor produces a PWM signal within around 40 secs from when it is first supplied.
PWM signal
Description of the signal
0%
Short circuit to earth of the signal line
20%
Non polluted air circulation
20%
Level 1 pollution
50%
Level 2 pollution
60%
Level 3 pollution
80%
Sensor error
100%
Short circuit to +12V signal line
If the AQS sensor has not been used for a long period its response time varies as described in the table later on.
Time not in use
Response time
< 24 h
max 1 sec
24 h < t < 76 h
max 30 sec
76 h < t < 480 h
max 180 sec
> 480 h
max 300 sec
In order to check the operation of the sensor:
- turn the ignition switch ON;
- wait 36 secs for the sensor to warm up;
- within 120 secs, inject pollutant gas into the sensor using a spray canister (part. N° 71715571);
- check that the result of the test is positive using the diagnostic equipment (Examiner).
Outside air temperature sensor
It is an NTC sensor fitted on the bottom of the left door mirror (right on right hand drive versions).
It is only fitted on versions with automatic climate control.
It supplies a signal proportional to the temperature of the outside air.
It is connected to the driver''s door control unit (NPG) which transmits the outside temperature signal via the CAN. The value transmitted via the CAN is always expressed in degrees °C.
The outside temperature should be measured with an accuracy of at least 0.5°C and with a tolerance of +/- 5%, including the tolerance of the sensor and the acquisition hardware.
The NCL uses this signal for the automatic control strategies.
If the data is missing or is not valid, the NCL uses the last valid figures and, after a period that can be adjusted, assumes a default value (which too can be adjusted in the EEPROM).
Depending on the outside temperature, the NQS warns the user of possible "ice danger" by means of a symbol and specific message.
e.