relay 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.
Pa
ge 43 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
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yp
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pair&id=AUDI.B5.HA01.01.1

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.
Pa
ge 44 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
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play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1

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

Pa
ge 46 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
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play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1

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.
Pa
ge 65 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
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yp
e=re
pair&id=AUDI.B5.HA01.01.1

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
Pa
ge 67 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
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e=re
pair&id=AUDI.B5.HA01.01.1

- 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
Pa
ge 68 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1