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

01-33

VAG1551 scan
tool display Possible cause
Corrective action
01270 4121
A/C Clutch N251)

Open circuit /SP












Continued on next
page - Short circuit or open circuit in wiring between A/C
compressor speed sensor -G111-2/3) and -E87-

- Open circuit in wiring between A/C Clutch Relay J44 and
N25
- Open circuit in voltage supply or in wiring/connections
between A/C clutch relay J44 and -E87-
- J44 malfunction
- N25 malfunction
- Malfunction in refrigerant circuit (A/C Compressor Speed
Sensor G111 not producing signals or compressor siezed2/3) - Diagnose and repair short or open
circuit in wiring using wiring diagram
- -G111- electrical test page 01
-
115

- Diagnose and repair open circuit
using
wiring diagram
- Diagnose and repair open circuit
using wiring diagram

- Replace -J44-
- Repair or replace -N25- page 87
-
85

- Replace -G111- page 87
-63
- Replace compressor page 87
-38
1)During m.y. 1996, Nippondenso type A/C compressors were installed as a running change. These compressors are not
equipped with A/C speed sensor G111. DTC at A/C Clutch -N25- are only detected only on compressors equipped with A/C
Compressor speed sensor G111.
2)Sender G111 produces 4 pulses for each compressor revolution.
3)A/C Clutch is switched on for a few seconds after engine starts.
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01-34

DTC 01270 continued
VAG1551 scan
tool display Possible cause
Corrective action
01270 4121
A/C Clutch N251)

Speed difference
too great /SP3)












Continued on
next page. - Ribbed belt loose, slipping



- A/C control head -E87- not coded correctly
- Loose terminal or contact resistance in circuit between
-N25- and A/C clutch relay -J44- or in wiring/connections
between -G111-2)4) and -E87-
- N25 slipping
- Incorrect crankshaft vibration damper (diameter)
- Malfunction in refrigerant circuit (compressor not
operating freely). - Check belt tension Repair Manual,
Engine Mechanical, Repair Group 13
Compare speeds of engine and compressor
using function 08 (Read measuring value
block) page 01
-63

- Code A/C control head -E87- according to
compressor type installed4) "Zexel" or
"Nippondenso" page 01
-57

- Diagnose and repair circuit using wiring
diagram and perform electrical tests
page 01
-115

- -G111-, -J44- electrical test page 01
-
115

- Repair or replace -N25- page 87
-85
- Check for proper vibration damper part
number
- Check compressor for free operation and
replace if necessary page 87
-38

1/2) Continued from page 01
-33

3) If speed difference is 30 % to 60 %, A/C Clutch is switched on again by -E87- for not more than 9 times during a driving
period (ignition off). If speed difference is greater than 60 %, A/C Clutch remains off until engine is started again.
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4) A/C compressor speed sensor G111 is not installed on Nippondenso compressors. If A/C control head -E87- is not coded
correctly according to compressor type, A/C Clutch -N25- will only engage briefly and shut off due to no speed signal input.
Pa
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01-35

DTC 01270 continued
VAG1551 scan tool
display Possible cause
Corrective action
01270 4121
A/C Clutch N251)

Mechanical
malfunction /SP2) - Belt and coupling pulley of -N25- are stuck together
- Short circuit to positive in wiring/connections between -
N25- and for A/C Clutch relay -J44-
- -J44- malfunction
- Short circuit to ground in wiring/connections between -E87-
and -J44- - Repair or replace -N25-
page 87
-85


- Diagnose and repair short
circuit using
wiring diagram

- Replace -J44-
- Diagnose and repair short
circuit using
wiring diagram.
01271 4122
Temperature Regulator
Flap Motor V68

Blocks or de-energized
/SP - Short circuit, open circuit or incorrect terminal assignment
(wires interchanged) of connectors between -V68- and -E87-
- Temperature flap sticking
- -V68- malfunction- Diagnose and repair short
circuit, open
circuit or confirm terminal
assignment using wiring
diagram
- Check for free operation of
temperature flap
- Test -V68- using function 03
(Output DTM)
page 01
-42

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01-38
Diagnostic Trouble Code (DTC) table, changes specific to vehicles 1997

Notes:
The following DTCs are no longer recognized beginning m.y. 1997:

00529 Speed info missing (sensor -G111- deleted).
00799 A/C engine coolant temperature (ECT) sensor -G110- (sensor deleted).
00801 A/C refrigerant high pressure switch -F118- (switch deleted).
01270 A/C clutch -N25- (Sensor -G111- deleted).
The following DTCs are new for 1997, or are current DTCs with additional references to 1997 changes. DTCs and component
references include various malfuction causes in the display below the DTC, etc.
VAG1551 scan tool display
Possible cause
Corrective action
00604
Back Pressure Flap Motor
Position Sensor -G113- in Air
Flow Flap Motor -V71-1)

Short circuit to ground /SP
Open circuit/short circuit to
positive /SP - Short circuit, open circuit in wiring or incorrect
terminal assignment (wires interchanged) of
connectors between -G113- and -E87-
- Air flow flap not operating freely
- -G113- in -V71- inoperative- Diagnose and repair short circuit,
open circuit in wiring or confirm
terminal assignment using wiring
diagram

- Check for free operation of air flow
flap3)
- Replace -V71-
Pa
ge 51 of 91 A/C s
ystem, On Board Dia
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)
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01-42

Output Diagnostic Test Mode (DTM)
(function 03)


Function
Output DTM allows functional checking of A/C
control head actuated components (DTM
components). Actuators receive output signals
generated by the control head via VAG1551
Scan Tool (ST) in sequence. Function is
confirmed in accordance with specified
responses.
The following components are tested in
sequence using Output DTM:

1 - A/C Clutch -N25-

2 - Fresh Air Blower -V2-

3 - Coolant Fan -V7-

4 - Fresh Air/Recirculating Flap Two-Way Valve
-N63-1)

5 - Temperature Regulator Flap Motor -V68-

6 - Central Air Flap Motor -V70-
Pa
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ystem, On Board Dia
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01-43
Notes:

During Output DTM on vehicles with Control Head (E87) Part Number 8D0 820 043 D, A/C Compressor Clutch (N25) DTC
"01270, mechanical malfunction SP" may be stored even though no malfunction is present. Corrective action: When
output DTM is complete, check DTC memory. If above DTC is present, erase DTC memory.
When starting Output DTM, temperature and air distribution flap flap motors move to pre-determined positions in
preparation for individual tests: Temperature Regulator Flap Motor V68: moves to "heat" position. Central Air Flap Motor -
V70- moves to "floor & defroster outlet" position. Footwell Defroster Flap Motor V85 moves to "defrost" position.
Output DTM can be repeated several times, if necessary.
During Output DTM, vehicle must not be moved and engine speed must be less than 3000 rpm.
During Output DTM, A/C system control is switched off and all segments in both A/C control head displays are actuated.
Interior temperature sensor fan -V42- is activated via an A/C control head:
with one display after activation of the coolant fan.
with two displays after activation of air flow flap motor.
Outside air temperature display -G106- is activated via an A/C control head
with one display after activation of air flow flap motor.
with two displays after activation of idle regulation.
Pa
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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.
Pa
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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).
Pa
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ystem, On Board Dia
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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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ystem, On Board Dia
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