Volvo: Volvo 850 turbo a/c, volvo 850 turbo wagon, test modes

Question
I have a 1994 Volvo 850 turbo wagon.A/C does not blow. Blower motor was tested and is ok. Resistor tested and ok. Lights flash on a/c control panel. My husband is a mechanic and is stumped. Any suggestions? Thanks.

Answer
Mike,
The flashing lights mean a fault is present in the climate system. Try to read the codes. Since you are sure of the blower itself and the resistor, I would say the control head for the climate system is at fault.




1994 Volvo 850 L5-2.3L Turbo VIN 57 B5234FT
Vehicle Level  Heating and Air Conditioning  Testing and Inspection  Initial Inspection and Diagnostic Overview  Description of On-Board Diagnostics  Initializing Test Modes


Initializing Test Modes
Notes
Manual Initialization :
The diagnostic unit is located on the right-hand side of the engine compartment. It can be used to run different test modes, involving entering control codes or reading off stored fault and acknowledgement codes.
All information on DTCs is held in the control module memory (EEPROM), even with the battery power off.
Once you have read off all DTCs, you can delete them. See: Deleting DTCS

Connection And Initialization :

Connect the selector cable to output 1 on diagnostic unit B.
Ignition on.
Go to "Reading Off Codes" and then continue with test mode 1, 2 or 4. See: Component Tests and General Diagnostics\Test Modes

Reading Off Codes :

The LED on the diagnostic unit flashes out the code. Each codes consists of a series of flashes with a short break between each series. Count the flashes in each series and write them down.

Code Structure :

Each code consists of three digits. Example: code 2 3 1. Reading off the code looks like this:
The number 2 is shown as two flashes, followed by a pause and then three flashes (3), another pause and one flash (1).
This code is then written as 2-3-1.
The control module memory can hold all different DTCs simultaneously. If faults have shown up a number of times when driving, but then returned to normal (intermittent faults), the DTCs will remain stored until deleted by an input code.
Only one code is displayed at a time. If a number of codes are stored, they are shown in ascending numerical order.
The codes used are:
DTCs, test mode 1.
Acknowledgement codes, test mode 2.
Control codes, test mode 4.
Transmission codes, test mode 4.