1993 Volvo 850 Programma A/C Climate Control (dual side)

RONALDCARNE

MEMBER
1993 VOLVO 850

Air Conditioning problem
1993 Volvo 850 Two Wheel Drive Automatic 156000 miles

I discovered a solder problem in the A/C controller and thus repaired same. After reinstallation, the lights still flash and the heat/AC still does not work. Do I need to do some sort of "reset" of the system to get it working? I did read your print out for self diagnostics but it did not explain if "resetting" is necessary. If my unit is still bad, I can get a used part reasonably but I want to be sure of the answer to this first. Thank you for your prompt reply.
Ron

1 Reply

DAVE H

MECHANIC
13,384 POSTS

Hello .. thanks for the donation .. much appreciated

It seems possible thet the DTC (trouble code) which was set when the fault originally occurred is still present in the ECC modules memory and needs to be cleared out of the ECC modules memory before the system will work again !! Unfortunately the only way to clear these codes is via Volvo diagnostic unit ?

Hope this helps ..let me know

SELF-DIAGNOSTICS
The Electronic Climate Control (ECC) control module can detect faults in the system and store Diagnostic Trouble Codes (DTC). If a fault is present, system informs driver by flashing the LEDs by the AC and REC switches for 20 seconds.
A fault warning is given when a fault is discovered or present, each time ignition is turned on, or engine started. DTCs will remain stored until cleared by an input code.
NOTE:Test Unit (981 3190) and Adapter (981 3194) are required for DTC diagnosis. The Volvo Diagnostic Key (998 8670) may be used to perform self-diagnostics. Follow tool manufacturer's instructions.

There are 3 different test modes/settings which can be selected for reading off DTCs. TEST MODE 1 may be used for reading off DTCs detected by control unit (up to 47 codes can be stored). TEST MODE 2 checks signals from speedometer and solar sensor.
TEST MODE 4 is used to check electrical circuits in A/C system, reset information on damper motor limit positions and change data transmission speed from ECC control module to on-board diagnostic unit.
NOTE:Ignition must be turned off before switching from one test mode to another.

ENTERING SELF-DIAGNOSTICS
Connect selector cable from diagnostic unit "A" to terminal No. 1 of diagnostic unit "B", located behind right headlight. See Fig. 2 .
Turn ignition on. LED on diagnostic unit "A" should start flashing. Each DTC (3-digits) consists of a series of flashes with a short break between each series. DTCs are displayed in ascending order.
Fig. 2: Identifying Diagnostic Units
Courtesy of VOLVO CARS OF NORTH AMERICA.