B & D Murkin
UK main importers for
Le Tonkinois varnish
Flexidisc sander
Le Tonkinois Varnish
Eberspacher wiring modern air heaters.
Airtronic D2  D4  D5, D1LCC D3LCC, D1LC D3LC D5LC
Eberspacher D1LCC & D3LCC
  





Eberspacher Airtronic D2  D4  D5 loom
I don't know how many versions of the loom there are, one version has no fuses in the loom, some looms will be home made.
Using one of the brown wires instead of the brown/white (pin 6) can cause problems. Details are in the Weird faults section in Faults page.
If the colours / connector are obviously wrong check if the heater is a non standard version, see Buying advice pages.
Connectors at the controller end of the loom are often cut off and different connectors could be used so use the cable colours as the main identification. Check with the pin numbers at the Eberspacher heater end of the cable if unsure.
Some power wiring joints are hidden inside the loom sheath.




D2 / D4 loom connector B1
This plugs into the Airtronic connector S1





D1LCC loom connector inside heater to ECU
White wires are for glow pin





Other end of our D1LCC loom, ex BT.
Large black connector temperature rheostat.
Smaller black connector diagnostic testing.
Twin wire connector battery supply
Two single connectors fuel pump
Triple wire connector BT 1 hour timer







Eberspacher D1LCC loom.
They were usually fitted with a rheostat temperature controller.
They had an old round type fuseholder with 20 Amp ceramic fuses. These are often corroded and unreliable so replace with a good quality blade type fuseholder. Eberspacher recommend increasing the blade fuse rating to 30 Amps as they have different characteristics to ceramic fuses.
Some power wiring joints are hidden inside the loom.
Many second hand D1LCC heaters are ex BT. These were fitted with a timer that allowed a maximum of 1 hours heating, the timer reset after a further hour. The timer could be removed and bypassed by joining the purple and yellow wires together.
Ex BT looms do not have the grey external temperature sensor wire.
One loom, possibly ex BT also had no brown/white wire. The controller used the brown wire instead. I installed a new brown/white wire.
D1LCC heaters sold now will probably be at least third hand so the wiring looms need checking as they may have been butchered.





Rheostat controller fitted into connector.




Rheostat connector.
On non BT loom yellow wire goes direct to pin 6
(in place of the purple wire)




Wiring connections cause many people problems when changing or maintaining their systems.
If you are not confident of your ability to install things safely or cannot understand my simplified guides leave it to the professionals!
Some mistakes can damage the ECU and be very expensive.
Always remove the fuse or disconnect the battery before doing work on the wiring.
The installation manuals cover many of the details and I used to recommend downloading and studying the manual before starting.
Eberspacher have stopped offering downloads for non current models, use the current manuals as a guide if manual is not available
Warning:- If you have bought an Eberspacher and it has a truck manufacturers name on the label it may be non standard so these wiring details do not apply, see our Buying advice page.



Users sometimes pick up odd lengths of cable with no indication of size.
As an example here are three mains cables to show relative size.
Cable sizes are the wire cross sectional area, not the diameter.
The 2.5mm2 cable is included for comparison as it is used for household ring main circuits so many people will know its size.
4mm2 cable was not available for these photos.
As a rough guide the 10mm2 wire which has 7 strands measures 4mm across the wire bundle and the 6mm2 cable 3mm across.
If the cable has more thinner strands the wire bundle might be smaller.


rt     red
bl     blue
ws   white
sw   black
gn   green
gr    grey
ge   yellow
vi     violet
br    brown
li     purple


Eberspacher Wiring Colour Codes.

  





Eberspacher manuals use these codes to indicate wiring colours.




Identifier
code
Pin
Wire colour

a1
1
Red
+12 volts power

2
-


3
-

a2
4
Yellow
Switch on input from controller,  (+12v = On)

5
Green/red
Pulsed output to pump
a8
6
Brown/white *
Reference earth to controller (0 volts)
a7
7
Grey/red
Set target temperature input, from controller
a6
8
Blue/white
Diagnostics signals, (serial data)

9
-


10
Brown
0 volts power (aka  Earth or negative supply)

11
-

a3
12
Grey
External temperature sensor input - optional

13
Blue
ADR (Hazardous goods) - usually not used

14
Blue/black
ADR (Hazardous goods) - usually not used

15
Pink
Car alarm - usually not used

16
Black/green
Output for external fan - usually not used
D2  D4  D5 Airtronic cable connector S1

  





Eberspacher Airtronic cable connector S1






Pump wiring
There are 2 wires for the pump,  green/red and green,  green/red and brown or green and green depending on model.
The pump is not polarity dependent, connect wires to the terminals either way round.
The pump may be mounted under the chassis, ensure adequate mechanical protection to the cables and connections.


Wiring Looms
Heaters have a variety of Looms even for the same heater but the wiring colours are usually standard on looms for these models.
Change all 12 volt references to 24 volt for 24 volt versions.

Battery supply.
The looms have 2 battery wires,  +12v  and earth.
These should be easy to identify, they will be the thickest wires in the loom, red +12 volts, brown earth (or negative).
Often they are too short and have to be lengthened.
Include a fuse in the +12 volt feed, 20 amp for D2 D4, 30 amp for all other air heater models including D5.
If you do not use an existing fuse fit a high quality blade type fuseholder. Cheaper low quality fuseholders are not designed for high current equipment and may burn out or cause unreliable connections.
Do not skimp on power cable size as doing so can cause unreliable operation due to low voltage problems.
Thinner cable is cheaper but you will regret using it later! (Full details on Low voltage page).
For a D2 / D4 Eberspacher recommend 4mm2 wires for up to 2.5m individual wire length; ie 2.5m positive wire and 2.5m return wire.
Increase the cable size to 6mm2 up to 4m, and 10mm2 or more for longer runs. That should give a cable loss of 0.25v or less.
The length calculation should include cables from the battery terminal to the connection point.
All other air models take about 20 amps during starting so recommended cable sizes are doubled.
The controller and other wiring carries less current so can be run in almost any normal cable thickness.


Controller connections
The remainder of the wires that need to be identified are for connections to the controller.
This is where most of the confusion arises as there are many different controllers and connector types.
I have tried several different ideas to simplify the wiring for users with limited technical knowledge with only partial success.
This time I am going back to the method of identifying these wires Eberspacher used in their earlier manuals.
For each heater model the wires needed are identified with a number , a1 to a9.
Each controller will also use the same identifier system. See Controller page.
This will allow any heater model to be connected to any compatible controller by joining wires with the same number.
The controller wiring carries low currents so can be run in almost any normal cable thickness.
Each heater generally has 4 wires for the controller plus wires for an optional remote sensor and diagnostics
You can ignore wires that are not used, just make sure they are insulated.
Airtronic D2  D4  D5

  





Identifier
code
Pin
Wire colour


1
Red thick
+12 volts power input from battery, comes via 20 Amp fuse at the end of the loom

1
Red
+12v input via 5 Amp fuse from ignition switch or battery, only fitted on some looms.
a1
1
Red thin
+12 volts output to controller

2
-


3
-

a2
4
Yellow
Switch on input from controller,  (heater on +12 volts, heater off 0 volts)

5
Green/red
Pulsed output to fuel metering pump
a8
6
Brown/white
Reference earth to controller (0 volts)
a7
7
Grey/red
Set target temperature input, from controller
a6
8
Blue/white
Diagnostics signals, (serial data)    Used by test equipment and some controllers

9
-


10
Brown thick
Negative power input from battery (also known as earth, ground, or 0 volts).

10
Brown
Negative power to fuel metering pump

10
Brown thin
Negative power (usually not used with most controllers)

11
-

a3
12
Grey
External temperature sensor input - optional, usually not used, 801 controller has a built in sensor

13
Blue
ADR (Hazardous goods) - usually not used

14
Blue/black
ADR (Hazardous goods) - usually not used

15
Pink
Car alarm - usually not used

16
Black/green
Vehicle fan control - usually not used
Identifier
code
ECU
Pin
Wire colour


1

?

2
White/red
?

3
Green/red
Pulsed output to fuel metering pump
a6**
4
Blue/white
Diagnostics signals, (serial data)    Used by test equipment and some controllers

5
Red thick
+12 volts power input from battery, (fused at 20 Amps round ceramic, or 30 amp flat blade fuses)
a1
5
Red thin
+12 volts output to controller

6
-

a7
7
Grey/red
Set target temperature input, from controller
a3
8
Grey
External temperature sensor input - optional, usually not used, 801 controller has a built in sensor

9
White
Glowpin

10
-


11
Brown thick
Negative power input from battery (also known as earth, ground, or 0 volts)

11
Brown med
Negative power to fuel metering pump

11
Brown thin
Negative power (usually not used with most controllers)

11
Brown thick
Glowpin

12
-

a8
13
Brown/white
Reference earth to controller (0 volts)
a2
14
Yellow
Switch on input from controller,  (heater on +12 volts, heater off 0 volts)
Eberspacher D1LC   D3LC  D5LC
  





D1LC  D3LC and D5LC heaters wiring colours are the same as the D1LCC D3LCC.
These older models had external electronics, the ECU pin numbers quoted above do not apply.
**The diagnostics blue/white wire works with modern controllers or test equipment
but will also provide an output suitable for flashing codes via a light on these models.

Identifier
code
Loom Wire colour

a1
Thin Red
+12 volts power to controller
a2
Yellow
Switch on signal from controller,  (+12v = On)
a7
Grey/red
Set target temperature from controller
a8
Brown/white
Reference earth to controller (0 volts)
a6
Blue / white
Diagnostics signals, (serial data), only used by some controllers and test equipment
a3
Grey
External temperature sensor input - optional

Thin Brown
0 volts power (aka  Earth or negative supply)
Usually only used as negative for indicator lights
Three additional wires may be used.

One of our D2 / D4 looms.
Left connector plugs into the Airtronic connector S1.
Upper right connector is for the controller.
White connector carries power and remote sensor.
Central connector is for fuel pump.


* The wire from the Airtronic to Pin 6 on the connector S1 may be coloured brown but functions as the brown/white.





Connector terminal removers.

  





It is virtually impossible to remove terminals from connectors without the correct extractor tool.
If you need to remove a terminal and know a friendly mechanic he might be able to do it for you.
Modern water heaters have several cables in one connector so parts like the motor cannot be removed.
I tried 2 types of reasonably priced extractors but they were not suitable.
At best I could remove about 1 terminal out of 10, don't waste money on them.
If anyone has working extractors and could donate them it we would be very grateful.
It would also make the task of photographing parts a lot easier.
We do not charge for the advice on these pages and do not use paid advertising.
As pensioners we are reluctant to buy items just for the benefit of the website.
Laser make very good terminal removal sets like the 19 piece 4027 and the 12 piece 4323.
The lowest prices for these sets that I have seen are in the 50 to 60 range.
They are aimed at professional vehicle mechanics. The extractors are not sold individually.








This is described in the Mouser catalogue as a
Junior Power Timer housing AMP 929504-6
Others are called Junior timer connectors.