DAF CF65, CF75, CF85 Series . Manual - part 34

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1-5

Hydronic 10 (ACH-EW) fault codes

HYDRONIC 10 (ACH-EW)

DAVIE XD diagnostics manual 

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1.3 EXPLANATORY NOTES TO FAULT CODES FOR HYDRONIC 10 (ACH-EW) 

WITH ELECTRONIC UNIT D979

The below explanatory notes to fault codes apply 

to the Hydronic 10 (ACH-EW) with the electronic 

unit D979. The electronic unit can be identified by 

the connector which is directly fitted in the unit.

Applicable to:

CF85 and XF95 (chassis number 

 0E621373) 

production date 

2003-37

K101651

Fault code

Fault code description with possible cause

Symptom

0-0

Internal communication fault in ECU (D979) due 
to:
-

defective ECU

-

Cab heater does not start or fails during 
operation

0-1

Internal communication fault in ECU (D979) due 
to:
-

defective ECU

-

Cab heater does not start or fails during 
operation

1-0

Fault when starting ACH-EW, no flame is 
detected within the start time. Flame sensor value 
remains below 80ºC, voltage on pins 15 and 16 of 
the 18-pin connector at the bottom of the ECU 
<2.23 V due to:
-

no or insufficient supply of fuel

-

insufficient supply of inlet air

-

clogged exhaust

-

fouled or damaged burner

-

voltage too high or too low during glowing

-

Cab heater does not start. After 2 failed 
starts the cab heater switches off and 
generates a fault.

1-4

Too many starts without flame detection due to:
-

no or insufficient supply of fuel

-

insufficient supply of inlet air

-

clogged exhaust

-

fouled or damaged burner

-

voltage too high or too low during glowing

-

Cab heater shuts down after 10 failed starts 
(20 start attempts) and the ECU will block

HYDRONIC 10 (ACH-EW)

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Hydronic 10 (ACH-EW) fault codes

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DAVIE XD diagnostics manual

2-0

Flame extinguishes repeatedly during operation 
due to:
-

no or insufficient supply of fuel

-

insufficient supply of inlet air

-

undervoltage or overvoltage

-

excessively high flame sensor temperature

-

excessively high overheating sensor 
temperature

-

defective combustion device

-

fouled or damaged burner

-

clogged or fouled exhaust

-

Cab heater fails or emits smoke and 
supplies insufficient heat

3-1

Voltage (>30 V for at least 20 seconds) on pins 
C2 and C3 of the ECU (D979) is too high due to:
-

excessive alternator/battery voltage

-

Cab heater fails during operation

3-2

Voltage (<20 V for at least 20 seconds) on pins 
C2 and C3 of the ECU (D979) is too low due to:
-

insufficient supply voltage, for example 
during starting

-

Cab heater fails during operation

4-0

Flame signalling when switching on. Flame 
sensor value above 80ºC, despite 4 minutes' 
cold-air ventilation; voltage on pins 15 and 16 of 
the 18-pin connector at the bottom of the ECU 
>2.23 V due to:
-

defective flame sensor

-

Cab heater does not start

5-1

Flame sensor short circuit on pins 15 and 16 of 
the 18-pin connector at the bottom of the ECU

-

Cab heater does not start or fails during 
operation

5-2

Open connection of flame sensor on pins 15 and 
16 of the 18-pin connector at the bottom of the 
ECU

-

Cab heater does not start or fails during 
operation

6-1

Short circuit in coolant temperature sensor on 
pins 14 and 18 of the 18-pin connector at the 
bottom of the ECU

-

Cab heater does not start or fails during 
operation

6-2

Open connection of coolant temperature sensor 
on pins 14 and 18 of the 18-pin connector at the 
bottom of the ECU

-

Cab heater does not start or fails during 
operation

7-1

Short circuit in fuel metering pump (B122) on pins 
C4 and C3 of the ECU

-

Cab heater does not start or fails during 
operation

7-2

Open connection in fuel metering pump (B122) 
on pins C4 and C3 of the ECU

-

Cab heater does not start or fails during 
operation

8-3

Combustion device speed deviation due to:
-

defective combustion device

-

defective electronic unit (D979)

-

Cab heater fails with a delay of 60 seconds 
during operation

9-1

Glow filament short circuit on pins 2 and 7 of the 
18-pin connector at the bottom of the ECU

-

Cab heater does not start

9-2

Open connection of glow filament on pins 2 and 7 
of the 18-pin connector at the bottom of the ECU

-

Cab heater does not start

10-0

Too fast a rise in coolant temperature due to:
-

poor flow of coolant

-

coolant shortage

-

use of intarder 

-

Cab heater fails during operation

Fault code

Fault code description with possible cause

Symptom

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Hydronic 10 (ACH-EW) fault codes

HYDRONIC 10 (ACH-EW)

DAVIE XD diagnostics manual 

6

10-4

ACH-EW safety function switched on as a result 
of:
-

too many overheatings

-

Cab heater fails. The ECU blocks after 3 
failed starts.

11-1

Short circuit in coolant circulation pump on pins 3 
and 6 of the 18-pin connector at the bottom of the 
ECU

-

Cab heater does not start or fails during 
operation

11-2

Open connection of coolant circulation pump on 
pins 3 and 6 of the 18-pin connector at the bottom 
of the ECU

-

Cab heater does not start or fails during 
operation

13-1

Overheating sensor short circuit on pins 11 and 
17 of the 18-pin connector at the bottom of the 
ECU

-

Cab heater does not start or fails during 
operation

13-2

Open connection of overheating sensor on pins 
11 and 17 of the 18-pin connector at the bottom 
of the ECU

-

Cab heater does not start or fails during 
operation

13-3

Difference between value of overheating sensor 
and value of coolant temperature sensor too large 
due to: 
-

poor flow of coolant

-

coolant shortage

-

use of intarder 

-

Cab heater does not start or fails during 
operation

15-1

Short circuit in wiring "signal ACH-EW on" to pin 
A1 on ECU ALS-S (D911)

-

No interior detection alarm system (ALS-S)

Fault code

Fault code description with possible cause

Symptom

HYDRONIC 10 (ACH-EW)

1-8

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Hydronic 10 (ACH-EW) fault codes

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DAVIE XD diagnostics manual