Opel Frontera UBS. Service manual — part 1172
6E–54
ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
D06RW085
Circuit Description
When air conditioning and blower fan are selected, and if
the system has a sufficient refrigerant charge, a 12-volt
signal is supplied to the A/C request input of the
powertrain control module (PCM). The A/C request
signal may be temporarily canceled during system
operation by the electronic thermostat in the evaporator
case. The electronic thermostat may intermittently
remove the control circuit ground for the A/C thermostat
relay to prevent the evaporator from forming ice. When
the A/C request signal is received by the PCM, the PCM
supplies a ground from the compressor clutch relay if the
engine operating conditions are within acceptable
ranges. With the A/C compressor relay energized,
voltage is supplied to the compressor clutch coil.
The PCM will enable the compressor clutch to engage
whenever A/C has been selected with the engine running,
unless any of the following conditions are present:
D
The throttle is greater than 90%.
D
The ignition voltage is below 10.5 volts.
D
The engine speed is greater than 4500 RPM for 5
seconds or 5400 RPM.
D
The engine coolant temperature (ECT) is greater than
125
°
C (257
°
F).
D
The intake air temperature (IAT) is less than 5
°
C
(41
°
F).
D
The power steering pressure switch signals a cramped
position.
Diagnostic Aids
To diagnose an the intermittent fault, check for the
following conditions:
D
Poor connection at the PCM–Inspect connections for
backed-out terminals, improper mating, broken locks,
improperly formed or damaged terminals, and poor
terminal-to-wire connection.
6E–55
ENGINE DRIVEABILITY AND EMISSIONS
D
Damaged harness–Inspect the wiring harness for
damage. If the harness appears to OK, observe the
A/C clutch while moving connectors and wiring
harnesses related to the A/C. A sudden clutch
malfunction will indicate the source of the intermittent
fault.
A/C Clutch Diagnosis
This chart should be used for diagnosing the electrical
portion of the A/C compressor clutch circuit. A Tech 2 will
be used in diagnosing the system. The Tech 2 has the
ability to read the A/C request input to the PCM. The Tech
2 can display when the PCM has commanded the A/C
clutch “ON.” The Tech 2 should have the ability to
override the A/C request signal and energize the A/C
compressor relay.
Test Description
IMPORTANT:
Do not engage the A/C compressor
clutch with the engine running if an A/C mode is not
selected at the A/C control switch.
The numbers below refer to the step numbers on the
Diagnostic Chart:
3. This a test determine is the problem is with the
refrigerant system. If the switch is open, A/C
pressure gauges will be used to determine if the
pressure switch is faulty or if the system is partially
discharged or empty.
4. Although the normal complaint will be the A/C clutch
failing to engage, it is possible for a short circuit to
cause the clutch to run when A/C has not been
selected. This step is a test for that condition.
7. There is an extremely low probability that both relays
will fail at the same time, so the substitution process
is one way to check the A/C Thermostat relay. Use
a known good relay to do a substitution check.
9. The blower system furnishes a ground for the A/C
control circuit, and it also shares a power source
through the Heater and A/C Relay. The blower
must be “ON” in order to test the A/C system.
A/C Clutch Control Circuit Diagnosis
Step
Action
Value(s)
Yes
No
1
Was the “On-Board Diagnostic (OBD) System Check”
performed?
—
Go to
Step 2
Go to
OBD
System
Check
2
Are any other DTCs stored?
—
Go to the
other DTC
chart(s) first
Go to
Step 3
3
1. Disconnect the electrical connector at the pressure
switch located on the receiver/drier.
2. Use an ohmmeter to check continuity across the
pressure switch.
Is the pressure switch open?
—
Go to Air
Conditioning
to diagnose
the cause of
the open
pressure
switch
Go to
Step 4
4
IMPORTANT: Before continuing with the diagnosis, the
following conditions must be met:
D
The intake air temperature must be greater than
15
°
C. (60
°
F).
D
The engine coolant temperature must be less
than 119
°
C (246
°
F).
1. A/C “OFF.”
2. Start the engine and idle for 1 minute.
3. Observe the A/C compressor.
Is the A/C compressor clutch engaged even though
A/C has not been requested?
—
Go to
Step 45
Go to
Step 5
5
1. Idle the engine.
2. A/C “ON”.
3. Blower “ON”.
4. Observe the A/C compressor.
Is the A/C compressor magnetic clutch engaged?
—
Refer to
Diagnostic
Aids
Go to
Step 6
6E–56
ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
(Cont'd)
Step
No
Yes
Value(s)
Action
6
1. Engine idling.
2. A/C “ON”.
3. Blower “ON”.
4. Observe the “A/C Request” display on the Tech 2.
Does the tool “A/C Request” display indicate “Yes?”
—
Go to
Step 34
Go to
Step 7
7
Temporarily substitute the A/C compressor relay in
place of the A/C thermostat relay, then repeat Step 5.
Did the “A/C Request” display indicate “Yes?”
—
Go to
Step 8
Go to
Step 9
8
Replace the original A/C thermostat relay.
Is the action complete?
—
Verify repair
—
9
Dose the blower operate?
—
Go to
Step 10
Go to
Step 11
10
Repair the blower.
Is the action complete?
—
Verify repair
—
11
Check for a faulty 10a A/C fuse in the underdash fuse
panel.
Was the 10A fuse OK?
—
Go to
Step 13
Go to
Step 12
12
Check for short circuit and make repairs if necessary.
Replace the 10A A/C fuse.
Is the action complete?
—
Verify repair
—
13
1. Ignition “ON.”
2. Use a DVM to check voltage at the positive A/C
switch wire (BRN).
Was voltage equal to the specified value?
+B
Go to
Step 15
Go to
Step 14
14
Repair the open wire (BRN) between the A/C switch
and the A/C fuse.
Is the action complete?
—
Verify repair
—
15
1. Remove the glove box to gain access to the A/C
thermostat.
2. Disconnect the thermostat connector.
3. Attach a fused jumper between ground and the
PNK/GRN wire at the thermostat.
4. A/C “ON.”
5. Blower “ON.”
Dose A/C request indicate “YES” on the Tech 2?
—
Go to
Step 16
Go to
Step 23
16
1. Ignition “ON.”
2. Use a DVM to check voltage at the electronic A/C
thermostat.
Was voltage equal to the specified value?
+B
Go to
Step 20
Go to
Step 17
17
Check for an open (LT GRN) between the thermostat
and the A/C switch.
Was the wire open?
—
Go to
Step 18
Go to
Step 19
18
Repair the open wire (LT GRN) between the thermostat
and the A/C switch.
Is the action complete?
—
Verify repair
—
6E–57
ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
(Cont'd)
Step
No
Yes
Value(s)
Action
19
Replace the A/C switch.
Is the action complete?
—
Verify repair
—
20
Use an ohmmeter to check continuity between the
electronic A/C thermostat and the blower switch.
Was there an open circuit?
—
Go to
Step 21
Go to
Step 22
21
Repair the open wire (GRN/YEL) between the
thermostat and the blower switch.
Is the action complete?
—
Verify repair
—
22
Replace the electronic A/C thermostat.
Is the an action complete?
—
Verify repair
—
23
Check for an open circuit between A/C thermostat relay
and PCM A/C request terminal (E-15).
Was there an open circuit?
—
Go to
Step 24
Go to
Step 25
24
Repair the open circuit between the PCM and A/C
thermostat relay.
Is the action complete?
—
Verify repair
—
25
Check for an open circuit between the A/C switch (LT
GRN) and the A/C thermostat relay (LT GRN).
Was there an open circuit?
—
Go to
Step 26
Go to
Step 27
26
Repair the open circuit between the A/C switch and the
A/C thermostat relay.
Is the action complete?
—
Verify repair
—
27
1. Ignition “ON.”
2. Use a DVM to check voltage at the A/C pressure
switch (BRN).
Was voltage equal to the specified value?
+B
Go to
Step 29
Go to
Step 28
28
Repair the open circuit between the 10A A/C fuse and
the pressure switch.
Is the action complete?
—
Verify repair
—
29
Use an ohmmeter to check continuity between the
pressure switch (GRN/WHT) and the A/C thermostat
relay (GRN/WHT).
Was the circuit open?
—
Go to
Step 30
Go to
Step 31
30
Repair the open circuit between the pressure switch
and the A/C thermostat relay.
Is the action complete?
—
Verify repair
—
31
Check for damaged pin or terminal at E-15 of the PCM.
Was a damaged pin or terminal found?
—
Go to
Step 32
Go to
Step 33
32
Repair the damaged pin or terminal.
Is the action complete?
—
Verify repair
—
33
Replace the PCM.
IMPORTANT: The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?
—
Verify repair
—
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