AUDI A4 1998 B5 / 1.G AC System On Board Diagnostic Repair Manual

01-44

Starting output Diagnostic Test Mode (DTM)

- Start engine, switch on compressor (press
"Auto" button), adjust air flow to center
instrument panel outlets only.

- Connect Scan Tool VAG1551 or 1552 in
operating mode -1-, enter address word 08 "A/C
Heating Electronics" and move forward in
program until "select function XX" appears in the
display.

- Switch on printer by pressing the PRINT button
(indicator lamp in button comes on).

- Check DTC memory page 01
-18
.

- Note any stored DTCs for reference and move
forward in program until "select function XX"
appears in the display. Rapid data transfer
HELP
Select function XX

Indicated on display (function selection)
- Press buttons -0- and -3-.
Rapid data transfer
Q
03 - Output Dia
gnostic Test Mode

Indicated on display
- Press -Q- button to confirm input.
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Output Dia
gnostic Test Mode
A/C Clutch - N25

Indicated on display
-
Advance through all DTM component checks using button.- Refer to output DTM table page 01
-46
to confirm function of DTM
components and test results.
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01-45

Notes:

If a DTM component fails to respond as
specified, perform all corrective actions, checks
and tests recommended in output DTM table
page 01
-46
.

A/C system component locations: engine
compartment page 87
-96
(note specific
model year information).

A/C system component locations: passenger
compartment page 87
-106
(note specific
model year information).

Output DTM can be ended by pressing the -C-
button.
After ending output DTM, check DTC memory
page 01
-18
.

If the readout "function unknown or cannot be
carried out at the moment" appears in the
display at the start of output DTM, e.g. when
engine not running, press button and once
again select "function 03 Output Diagnosis Test
Mode (DTM)" (DTM component "A/C Clutch
N25" is no longer actuated for this test).
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If the readout "function unknown or cannot be
carried out at the moment" appears in the
display page 01
-63
, Read measuring value
block (display group 1).
Function is unknown or cannot be carried out at the moment!

Indicated on display
- If this readout appears in the display, output Diagnostic Test Mode
(DTM) is ended.
- VAG1551 Scan Tool (ST) can be returned to the function mode by
pressing the button.
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01-46
Output Diagnostic Test Mode (DTM) table

VAG1551 scan tool display
Specified function
Corrective action
A/C Clutch N25








Notes: - N25 clicks every 2-seconds
- Output of A/C control head -E87- is switched from 0 V to
12 V every 2-seconds2) - Test voltage supply for -
N25- (via A/C Clutch
Relay J44) using wiring
diagram
- Repair or replace -N25-
page 87
-90

- Test circuit and
connectors between A/C
control head -E87-, J44
and -N25- using wiring
diagram
- Replace -E87-

"A/C compressor on" output to
Engine Control Module (ECM)
and -E87- terminal -C12- is
also actuated at the same
time1)
Output of -E87- switched from 0 V to 12 V every 2
seconds can be confirmed by switching compressor on
and off using the "ECON" button while reading the
measured value block of engine control module
Repair Manual, Fuel Injection and Ignition System,
Repair Group 01)

1)Test this "A/C compressor on" signal only if complaints exist. ECM uses signal to compensate for engine load when
compressor engages Repair Manual, "Fuel Injection & Ignition," Repair Group 24 . ECM is capable of switching off the A/C compressor from this signal. Confirm via function 08, Read measuring value block,
page Page 01
-63
, display group 01 and Fuel Injection and Ignition System Repair Manual, Repair group 01: Read
measured value block of ECM with engine running and at same time switch compressor on and off.
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2)A/C Clutch -N25- cannot be actuated during Output DTM when certain compressor cut-off conditions exist, page 01
-63
,
Read measuring value block.
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01-47

VAG1551 scan tool
display Specified function
Corrective action
Fresh Air Blower V2





Caution:
Coolant Fan coming on !
Warning:
The next forwarding of program with the
button will cause Coolant Fan V7 to come
on. Keep clear of Coolant Fan! - V2 runs for 2 seconds with 0V, 3V, 6V, 9V,
12V, 15V, 0V applied.
- Check that fresh air blower operates freely
- Test ground connection to Control Module
for Fresh Air Blower J126 using wiring
diagram
- J126 electrical test page 01
-115
- Replace -E87-
Coolant Fan V7
- V7 (1st stage) switched on and off every 5
seconds - Test wiring/connections between -E87- and
J26 for open circuit or short circuit to positive
using wiring diagram
- Coolant Fan Control (FC) Relay J261)
electrical test page 01
-115

- Replace -E87-
Fresh Air/Recirculating
Flap Two-Way Valve N63
2) - N63 switches from fresh air to recirculating
air every 5 seconds - Check vacuum supply to -N63-
page 87
-187

- Test voltage supply to N63 and circuit to -
E87- for open circuit or short circuit to ground
using wiring diagram
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- Check vacuum unit for -N63-
- Replace N63
1)Coolant fan 2nd stage is controlled by Second Speed Coolant Fan Control (FC) Relay J101:
When Coolant Fan Control (FC) Thermal Switch F54 closes and when A/C Refrigerant High Pressure Switch F23 closes
2)-N63- deleted for m.y. 1997
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01-48

VAG1551 scan tool display
Specified function
Corrective action
Temperature Regulator Flap
Motor V68




Note:

Wait until temperature flap
is in "heat" position before
pressing button
- V68 moves from stop to stop (fresh air
blower running, temperature of air at outlets
changes) - Test wiring/connections between V68
and -E87- for open circuit or wrong
connection using wiring diagram
- Check for free operation of temperature
flap
- V68 electrical test page 01
-115
- Replace -E87-
Central Air Flap Motor V70


Notes:

Wait until central flap is at
"air distribution to footwell/
defroster flap" position
before pressing button Close all instrument panel
air outlets. - -V70- moves from stop to stop (fresh air
blower running, air flow switches from
footwell/defrost to instrument panel air
outlets) - Test wiring/connections between -V70-
and -E87- for open circuit or wrong
connection using wiring diagram
- Check for free operation of central flap
- -V70- electrical test page 01
-115
- Replace -E87-
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01-49

VAG1551 scan tool display
Specified function
Corrective action
Footwell/Defroster Flap Motor V85




Note:

Wait until footwell/defroster flap is
at "defrost" stop before pressing
button.
- V85 moves from stop to stop
(fresh air blower running, air flow
switches from footwell to defrost) - Test wiring/connections between V85 and -
E87- for open circuit or wrong connection
using wiring diagram
- Check for free operation of
footwell/defroster flap
- V85 electrical test page 01
-115
- Replace -E87-
Air Flow Flap Motor V71 1)
- V71 moves from stop to stop
(fresh air blower running, air flow
changes) - Test wiring/connections between V71 and -
E87- for open circuit or wrong connection
using wiring diagram
- Check for free operation of air flow flap
- V71 electrical test page 01
-115
- Replace -E87-
1) For m.y. 1997, -V71- operates the air flow flap as well as the fresh/recirculated air flap.
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