AC won't cool?

AUTUMNJADE10

MEMBER
2002 SAAB 9-3
4 CYL
FWD
AUTOMATIC
98,000 MILES

HI;
I have had the air checked several times.I have freon in. The compresser is fine, no leaks, and the electrical is ok. Fuses are also good.
They have narrowed it down to the computers. I would like to know if you think it could be a sensor that may be causing the problem, or are there 2 computers in the dash that either one could be the problem. No cold air at all, just blows hot.
Also, if it is the DICE computer, or the control head, I believe that is what one said, do you have an idea of how much this would cost. Or the other computer. Any info you can give me before I take it in again, would be appreciated.

1 Reply

DAVE H

MECHANIC
13,383 POSTS

Hello.. thanks for the donation .. much appreciated

have you checked for fault codes on the A/C system ? I would be checking the sensors and blend door motor before replacing the control module

It is our experience that the majority of control modules returned to us for repair or replacement under warranty are in perfect working order. In these cases, fitting a new control module has obviously not cured the fault. Therefore, go through all the following points carefully before changing the control module:
Check the latest edition of TIS2000 to see whether the problem can be solved with a control module software update (for control modules that can be reprogrammed).

The cabin temperature sensor is positioned in the dashboard under the ACC unit. The unit has a built-in suction fan that draws cabin air past an NTC resistor.
The cabin temperature sensor in the most important value for the ACC unit and is compared to the cabin temperature in order to decide if the mixed-air temperature should be increased or decreased.
The cabin temperature is adjusted with respect to the outside temperature so that the temperature experienced matches the set temperature. As the difference between selected temperature and adjusted temperature increases, the ventilation fan speed will also increase.
When the ignition is turned off, the suction fan will continue to operate for approximately 10 minutes. This decreases the risk of incorrect temperature value when restarting after a short stop.
IMPORTANT:The cabin temperature gives an incorrect value if the cigarette lighter/cover is not fitted. This is due to warm air being drawn from the rear of the dashboard through the socket for the cigarette lighter and into the cabin temperature sensor. The cabin temperature sensor must not be positioned in any other location in the dashboard.

Diagnosis
In case of an open circuit or short circuit, diagnostic trouble code B1350 is generated, and 02 is shown instead of temperature at calibration.
The outside temperature is used as replacement value when the ignition is turned on and then the calculated head level temperature for the front seat passenger and driver is used.
Mixed-air temperature sensor
Fig. 115: Mixed-Air Temperature Sensor - Communication Diagram
Courtesy of SAAB-SCANIA OF AMERICA, INC.
Fig. 116: Mixed-Air Temperature Sensor - Circuit Diagram
Courtesy of SAAB-SCANIA OF AMERICA, INC.
The mixed-air temperature sensor is of the NTC type and has a pointed sensory body inserted into one of the climate control unit floor outlets.
The location in the floor outlet depends on the fact that the air is completely mixed at this point and that the air requirement of the sensor is fulfilled, regardless of air distributor position, due to a controlled leak.
When the ACC control module has decided which mixed-air temperature that is required, the measured value from the mixed air sensor is used to adjust the position of the air-mixing damper.
If the selected temperature is "HI" or "LO ", the mixed-air sensor value is not used.
Diagnosis
In case of an open circuit or short circuit, diagnostic trouble code B1347 is generated, and 04 is shown instead of temperature at calibration.
A value based on the relative opening of the air-mixing damper multiplied by the coolant temperature is used as a replacement value.
Solar sensor
Fig. 117: Solar Sensor - Communication Diagram
Courtesy of SAAB-SCANIA OF AMERICA, INC.
Fig. 118: Solar Sensor - Circuit Diagram
Courtesy of SAAB-SCANIA OF AMERICA, INC.
The solar sensor is located on top of the dashboard. It mainly measures the infrared radiation (heat radiation).
In case of increased solar radiation and outside temperatures above +15 °C, the ACC control module increases the ventilation fan speed since additional cooling is required. The fan speed changes immediately when the solar radiation changes.
The fact that the solar sensor mainly measures infrared radiation (heat radiation) means that it cannot be tested using a fluorescent light, sun light or incandescent light must be used.
Adjusting
The ACC unit can be adjusted using the diagnostics tool to consider a greater or smaller amount of the solar sensor value for the cabin temperature calculation.
Diagnosis
In case of an open circuit or short circuit, diagnostic trouble code B1340 is generated, and 03 is shown instead of temperature at calibration.
The latest valid value is used as a replacement value. When the ignition is turned on, 0 W/m 2 is used.
Ventilation fan