INFORMATION AND REPAIR

Diagnostic trouble codes (DTCs)

If the control module detects a fault, it stores a diagnostic trouble code (DTC) and the orange LEDs in the REC and the air conditioning (A/C) buttons flash for approximately 20 seconds. The control module can store up to 38 diagnostic trouble codes (DTCs). If the total diagnostic trouble codes (DTCs) exceeds 10 the five first diagnostic trouble codes (DTCs) will always be saved, while the last five become the latest diagnostic trouble code (DTCs) to be stored.
If for some reason a fault disappears after the diagnostic trouble code (DTC) has been permanently stored in the control module, information about the fault is stored in the control module.
Every diagnostic trouble code (DTC) has a counter which records the number of cycles which have been fault-free since the diagnostic trouble code (DTC) was stored (intermittent fault). A cycle is defined from when the ignition was turned on, was then on for at least 10 seconds and then turned off. Every time the cycle runs without the control module registering the fault again, increases the counter by 1. Using the counter, it is possible to determine if the control module interprets diagnostic trouble code (DTC) as permanent or intermittent. When the counter is at 0 the transmission control module (TCM) treats the fault as a permanent fault. If the counter value is greater than 0 the control module interprets this as meaning the fault is intermittent.

Diagnostic functions

The Volvo on-board diagnostic (OBD) system functions are activated by pressing the REC button on the unit. The following functions are available:
— 1 reading off diagnostic trouble codes (DTCs) (initiated by pressing button twice)
— 2 self-adjustment of the damper motors (initiated by pressing button three times)
— 3 erasing diagnostic trouble codes (DTCs) (initiated by pressing button four times)
Refer to the picture for information on how to initiate the sequences and how to interpret the flashes from the indicator LED.
Note! The REC button has to be in the ON position (pressed in) and then pressed again (OFF position) to be counted as part of the sequence.
To activate diagnostics:
— The ignition must be ON
— The battery voltage must be normal.

Self-adjustment of blend door motors

The blend door motors are self-adjusting after any of them has been removed or replaced, or other work is carried out on the motor or linkage.

To activate self-adjustment, proceed as follows:

Ignition ON, position I or II
press in the REC button three times within three seconds.

NOTE! The button must be pressed within three seconds of the ignition being turned on!

NOTE! The control module automatically does a self-adjustment when it is connected to the car or when it registers that the power has been disconnected (e.g. battery disconnected) for more than 30 seconds.

How does the blend door motor function?

The motor sends a voltage signal back to the controller between 0.5V to 4.8V.

Based on the user's desired temperature, the motor turns to a desired position based on the voltage signal back from the motor.

If the motor turns more than the voltage limits, the calibration errors out and the motor is stuck in position until a calibration is successful.

Why does my blend door motor not calibrate?

I would say there are two main reasons the motor does not calibrate.

The motor has an internal fault such as a failed component
The black plastic shaft which the square drive slots into has cracked. When this square hole cracks, the shaft slips inside the square hole and prevents the motor from finding the two limit points.

How to fix the cracked black plastic input shaft

I bought "Brass Round Tube 300mm Length 11mm OD 0.5mm Wall Thickness" I cut this into a 3mm wide piece and hammered it on the end of the rod to clamp it shut.

This prevents the square drive of the motor slipping inside the hole and lets the motor calibrate.