Checking auxiliary air heater element Z35 — VW

Checking
auxiliary air heater element
Z35
Note
Auxiliary air heater element
Z35
peripherals (load signal for alternator terminal DF,
low heat output relay
J359
,
high heat output relay
J360
,
intake manifold temperature sender
G72
,
coolant temperature sender
G62
) can be read via the engine control unit self-diagnosis.
Checking
Special tools and workshop equipment required
Hand multimeter
V.A.G 1526D
Multimeter
V.A.G 1715
Auxiliary measuring set
V.A.G 1594C
Digital potentiometer
V.A.G 1630
Vehicle diagnosis tester
Current flow diagrams, electrical fault finding and fitting locations
Test conditions
Intake temperature less than 19° C
Coolant temperature less than 80° C
Passenger compartment temperature about 20° C
Battery voltage greater than 11 V
Alternator load not greater than 50 % (terminal DF)
Engine speed greater than 450 rpm
Blower speed 4 for
fresh air blower
V2
Turn rotary knob for interior temperature to end position for maximum temperature.
Test procedure
If the specifications for intake and coolant temperature are not attained, create the following test conditions.
The intake manifold temperature sender is located together with the intake manifold pressure sender in a separate housing on intake manifold.
Connect
digital potentiometer
V.A.G 1630
to connector of intake manifold temperature sender between contacts 1 and 2.
Specification: see diagram.
Area
A
shows the resistance values for the temperature range 0…50 °C and area
B
, the values for the temperature range 50…100 °C.
Examples:
10 ℃ correspond to a resistance of 3500…4000 Ω
80 ℃ correspond to a resistance of 275…375 Ω
Pull connector off
coolant temperature sender
G62
.
Connect
digital potentiometer
V.A.G 1630
to connector of
coolant temperature sender
G62
between contacts
1
and
2
.
Specification: see diagram.
Area
A
shows the resistance values for the temperature range 0…50 °C and area
B
, the values for the temperature range 50…100 °C.
Examples:
40 °C correspond to a resistance of 1000…1500 Ω
80 ℃ correspond to a resistance of 275…375 Ω
Connect
multimeter
V.A.G 1715
to supply wire for
auxiliary air heater element
Z35
using pick-up clamp.
Set
multimeter
V.A.G 1715
to ampere test.
Ten seconds after the engine has been started, the
auxiliary air heater element
Z35
is enabled for heating by the
diesel direct injection system control unit
J248
. The 3 heater elements are switched on and off by the engine control unit in stages via relays.
Start engine and allow it to idle.
If air conditioning is fitted, switch it off.
The starting current for
auxiliary air heater element
Z35
is approx. 38.9 A and more at the set test conditions. After a heating phase of about 10 minutes for the
auxiliary air heater element
Z35
, the current consumption drops to about 31.6 A. Should the figure drop by a further 10 A or more, check voltage supply cables according to the current flow diagram
Current flow diagrams, Electrical fault finding and Fitting locations
.
If no fault is found in the wiring
Renew
auxiliary air heater element
Z35
Chapter
.
Clear event memory.