AHE test of electrical system metering pump, temperature circuit breaker, control module open circuit

AD83.70-W-6000-22A

AHE test of electrical system metering pump, temperature circuit breaker, control module open circuit





Scope of test

Measuring instrument/

Test connection

Operation/Requirement

Specified value

 Possible cause/Remedy

1.0



Metering pump,

Temperature-controlled cutout,

Control unit –//–

Internal resistance

a 

M16



 b

 Check fuse F6/A5, replace if necessary.

fuse trips again 

AD83.70-W-6000-42A

Ignition: OFF

Heater unit: OFF

(Run-on phase must have ended).

Disconnect plug connection on metering pump (M16).

Carry out measurement directly on both connections (on front right vehicle longitudinal frame, follow fuel line if necessary).

3050 Ω

Value > 30 kΩ:

 Replace metering pump (M16) (–//–)

Value in order:

 Inspect plug on metering pump (M16) (corrosion) if necessary.

 1.1

1.1

Metering pump,

Temperature-controlled cutout,

Control unit –//–

Resistance of complete electric circuit of metering pump (M16)

C1 

Z14



 C2

Ignition: OFF

Heater unit: OFF

Re-connect plug connection on metering pump (M16).

Disconnect plug connection C on control unit (Z14).

Carry out measurement at both connections from plug sleeve housing C.

3050 Ω

Value > 30 kΩ:

 Cable harness (–//–) to metering pump (M16)

 1.2

Value in order:

 Open-circuit in temperature-controlled cutout, in control unit or possibly on one plug connection / cable harness to temperature-controlled cutout, if necessary

 1.3

1.2

Metering pump,

Temperature-controlled cutout,

Control unit –//–

Cable harness to metering pump (M16)

2/1 

FF38



 2/2

Ignition: OFF

Heater unit: OFF

Disconnect plug connection FF38 under electrical compartment.

Carry out measurement at both connections from plug sleeve housing FF38.

3050 Ω

Value > 30 kΩ:

 Check short cable harness on fuel metering pump (M16) and both cables from FF9 to FF38 (under electrical compartment).

If no fault can be determined:

Inspect plug connections on cable harness from electrical compartment (FF38) to metering pump (on front right vehicle longitudinal frame), replace cable set if necessary.

Value in order:

 Inspect plug connections on cable harness from electrical compartment (FF38) to FF9 and to control unit (Z14), install new cable harness if necessary.

1.3

Metering pump,

Temperature-controlled cutout,

Control unit –//–

Circuit

Temperature-controlled cutout

A4 

Z14



 A5

Ignition: OFF

Heater unit: OFF

Re-connect plug on metering pump (M16).

Disconnect plug connection A on control unit.

Carry out measurement at plug sleeve housing A.

Value > 30 kΩ:

 1.6

Value < 5 Ω:

 1.4

 Possible loose contact:

Re-connect all plug connections, switch on ignition, erase fault memory and switch on heater unit.

Then tap / shake plugs while observing HHT display. Fault cause is located at point where fault code  re-appears.

 1.5

1.4

Metering pump,

Temperature-controlled cutout,

Control unit –//–

Internal resistance

Control unit

C1 

Z14



 A5

Ignition: OFF

Heater unit: OFF

Disconnect plug connection A and C on control unit (Z14).

Carry out measurement at plug A and C.

Value > 30 kΩ:

 Replace control unit (Z14).

1.5

Metering pump,

Temperature-controlled cutout,

Control unit –//–

Resistance





Z14



Z14



 C1

 C2

Ignition: OFF

Heater unit: OFF

Disconnect plug C on control unit (Z14).

Ignition: ON

Carry out measurements at plug C to ground.

< 20 V

 Cables

1.6

Metering pump,

Temperature-controlled cutout,

Control unit –//–

Internal resistance

Temperature controlled cutout

a 

X7



 b

Ignition: OFF

heater unit (take care not to disconnect coolant circulation), if necessary refer to 

AD83.70-W-2000-16A

 Danger!

Risk of injury and of scalding with high coolant temperature!

AS83.70-Z-0002-01A

AS20.00-Z-0001-01A

Disconnect plug connection on heater unit.

Carry out measurement directly on plug X7 AD83.70-W-2000-18A.

Value > 30 kΩ:

 Inspect plug X7 for corrosion.

 Replace temperature-controlled cutout complete with cable and plug X7 if necessary.

 Allow heater unit to cool down if necessary and collect draining coolant.

Value < 5 Ω:

 Inspect plug on heater unit for corrosion, if no fault can be determined:

 1.7

1.7

Metering pump,

Temperature-controlled cutout,

Control unit –//–

Supply cable

14/5 

G



 14/7

Ignition: OFF

Heater unit: OFF

Re-connect plug connection on heater unit.

Carry out measurement at plug housing behind air recirculation box.

Value > 30 kΩ:

 Inspect 14-pin plug on blower for corrosion.

 Replace cable harness to heater unit complete with molded connection plate if necessary.

Value < 5 Ω:

 Plug connection / cable –//–

 Inspect cable harness from air recirculation box to control unit (Z14) if necessary:

 1.8

1.8

Metering pump,

Temperature-controlled cutout,

Control unit –//–

Supply cable

14/5

FF8



14/7

Ignition: OFF

Heater unit: OFF

Re-connect 14-pin plug connection on blower.

Carry out measurement at plug sleeve housing FF8 under electrical compartment.

Value > 30 kΩ:

 Plug connection / cable (–//–) from air recirculation box to electrical compartment.

Value < 5 Ω:

 Plug connection / cable –//–

 Inspect cable harness from control unit to electrical compartment (FF8), fit new cable if necessary (use 1 mm2, blue).