air conditioning RENAULT SCENIC 2008 J84 / 2.G Engine Compartment Connection Unit Workshop Manual

ENGINE COMPARTMENT CONNECTION UNIT
Fault finding - System operation87G
87G-8V7 MR-372-J84-87G050$110.mif
UPC
Vdiag No.: 48, 4CENGINE COMPARTMENT CONNECTION UNIT
Fault finding - System operation
General operation
The Protection and Switching Unit is involved in the following functions:
–Access - Safety.
–Air conditioning.
–Lighting.
–Wipers.
–Charging circuit.
–Oil pressure detection.
–Electric power distribution.
1 - Electric power distribution
The main function of the Protection and Switching Unit is to switch and distribute the power supply to the vehicle's
systems, actuators or computers.
Part of this function is handled within the unit, but it is not electronically controlled by the computer.
+ 12 V battery feed
The Protection and Switching Unit receives energy from the battery via the Busbar and MM connectors (tracks 6 and
4) and redistributes the + 12 V feed.
+ 12 V after ignition
The UCH sends the Protection and Switching Unit the + 12 V after ignition feed request via the multiplex network.
When the Protection and Switching Unit receives this request, it actuates the after ignition relay unconditionally. The
signal is distributed to the sensors, actuators and computers.
2 - Charge circuit
One of the main functions of the Protection and Switching Unit is managing the charge circuit.
Purpose and components:
The main function of the charging circuit is to produce and distribute the electrical energy required to operate the
various electrical consumers on the vehicle (computers, lights, etc.).
It is also used to start the engine.
The main components are a battery, an alternator and a starter motor.
MR-372-J84-87G050$110.mif

ENGINE COMPARTMENT CONNECTION UNIT
Fault finding - System operation87G
87G-10V7 MR-372-J84-87G050$110.mif
UPC
Vdiag No.: 48, 4C
Only on vehicles with M9R injection:
The injection computer also acts on the alternator regulation voltage. The injection computer sends the maximum
authorised power delivered by the engine, to the UPC computer via the multiplex network. If the power from the engine
is less than the power consumed by the alternator, the UPC computer will reduce the alternator voltage.
For vehicles with any injection type except M9R:
The UPC sends the alternator charge to the injection to regulate the idling speed.
c) Starter
This turns the engine over to make it start, and requires a very powerful electric current, which the battery must be
able to supply.
The computer receives the starter activation request via the multiplex network from:
–injection,
–UCH,
–the automatic gearbox.
(see ET010 Starting conditions met)
The computer controls the starter relay.
In the event of a fault with the starter, refer to section 16A, Starting - Charging, Starter.
3 - Keyless vehicle
Under the keyless vehicle function, the Protection and Switching Unit is involved in the starting sub-function. The
computer:
–receives the supply request from the passenger compartment starter via the multiplex network, as well as the clutch
pedal position,
–controls the starter relay,
–inhibits or cuts out this relay control according to a signal prohibiting starting which is sent by the injection computer
or gearbox via the multiplex network (see 87B, Passenger compartment connection unit).
4 - Air conditioning
For the operation of the air conditioning and the role of the Protection and Switching Unit in the control of this
function (see 62A, Air conditioning).
Cold loop:
The computer receives the compressor switch-on request from the injection via the multiplex network.
The computer controls the compressor clutch engagement relay.
Heating:
The computer manages the alternator charge and sends back the signal over the multiplex network.
The computer also controls the rear screen de-icing.

ENGINE COMPARTMENT CONNECTION UNIT
Fault finding - System operation87G
87G-12V7 MR-372-J84-87G050$110.mif
UPC
Vdiag No.: 48, 4C
9 - Injection
The Protection and Switching Unit is involved in injection operation, relating to supplying the computer and its
sensors.
Supply malfunctions may lead to engine management customer complaints (rough idle, etc.).
10 - Fuse fault finding
The Protection and Switching Unit can detect the condition of its fuses and indicate faults using:
DF014 LEFT-HAND SIDE LIGHT CIRCUIT.
DF015 RIGHT-HAND SIDE LIGHT CIRCUIT.
DF016 LEFT-HAND DIPPED HEADLIGHT CIRCUIT.
DF017 RIGHT-HAND DIPPED HEADLIGHT CIRCUIT.
DF018 LEFT-HAND MAIN BEAM HEADLIGHT CIRCUIT.
DF019 RIGHT-HAND MAIN BEAM HEADLIGHT CIRCUIT.
DF020 FRONT FOG LIGHT CIRCUIT.
DF021 REVERSING LIGHT(S) CIRCUIT.
DF022 REAR SCREEN DE-ICER CIRCUIT.
DF023 FRONT WINDSCREEN WIPER CIRCUIT.
DF024 GAS COMPUTER SUPPLY.
DF025 AIRBAG/ELECTRIC POWER-ASSISTED STEERING SUPPLY.
DF026 AUTOMATIC TRANSMISSION SUPPLY.
DF029 STEERING COLUMN LOC/ENGINE MANAGEMENT SUPPLY.
DF030 AIR CONDITIONING COMPRESSOR SUPPLY CIRCUIT.
DF031 HEADLIGHT WASHERS SUPPLY CIRCUIT.
DF032 + 12 V RELAY SUPPLY CIRCUIT.
DF036 STEERING COLUMN LOCK SUPPLY CIRCUIT.
To carry out fault finding on the fuses, run command AC016 Test electrical supply circuits.
If a fuse is faulty, the associated fault becomes STORED.
Once the fuse has been replaced or the repair completed, run command AC016 Test electrical supply circuits
again to clear the fault.
Protection and Switching Unit Version
There are 4 Protection and Switching Unit versions:
–N1: vehicle with a 340 W fan assembly.
–N2: vehicle with a 460 W fan assembly.
–N3: vehicle with a 550 W fan assembly (external relay).
–N4: vehicle with 340 W, 460 W or 550 W fan assemblies + automatic transmission and/or LPG and/or with
headlight washers.

ENGINE COMPARTMENT CONNECTION UNIT
Fault finding - Conformity check87G
87G-58V7 MR-372-J84-87G050$440.mif
UPC
Vdiag No.: 48, 4C
FUNCTION: AIR CONDITIONING
SUB-FUNCTION: HEATING
NOTESOnly carry out this conformity check after a complete check with the diagnostic tool
(fault reading and configuration checks).
Application conditions: engine stopped, + after ignition feed on.
FunctionParameter or Status
Check or ActionDisplay and Notes Fault finding
Alternator chargePR010:Alternator charge0 < X < 99.6%
With the engine running,
activate the heated rear
screen and check that the
value increases.In the event of a fault, consult
the interpretation of
parameter PR010.
Rear screen de-
icerAC011:Rear screen de-
icerThis command supplies
the rear screen and door
mirror heating resistors, if
fitted to the vehicle.
They should be warm. In the event of a fault, apply the
procedure for dealing with
command AC011.

ENGINE COMPARTMENT CONNECTION UNIT
Fault finding - Conformity check87G
87G-59V7 MR-372-J84-87G050$440.mif
UPC
Vdiag No.: 48, 4C
FUNCTION: AIR CONDITIONING
SUB-FUNCTION: COLD LOOP
NOTESOnly carry out this conformity check after a complete check with the diagnostic tool
(fault reading and configuration checks).
Application conditions: engine stopped, + after ignition feed on.
FunctionParameter or Status
Check or ActionDisplay and Notes Fault finding
Compressor
controlAC008:Compressor
controlYou should be able to hear
the compressor clutch
(stops the motor running).In the event of a fault, apply the
procedure for dealing with
command AC008.
Fan assemblyAC009:Low-speed fan
assemblyThis command is used to
activate the fan assembly
at low speed.In the event of a fault, apply the
procedure for dealing with
command AC009.
AC010:High-speed fan
assemblyThis command is used to
activate the engine cooling
fan at high speed.In the event of a fault, apply the
procedure for dealing with
command AC010.
Low-speed
engine fan
assembly relay
controlET014:Low-speed
engine fan
assembly relay
controlINACTIVE
ACTIVEIn the event of a fault, consult
the interpretation for status
ET014.
High-speed
engine fan
assembly relay
controlET013:High-speed
engine fan
assembly relay
controlINACTIVE
ACTIVEIn the event of a fault, consult
the interpretation for status
ET013.

ENGINE COMPARTMENT CONNECTION UNIT
Fault finding - Interpretation of commands87G
87G - 82V7 MR-372-J84-87G050$770.mif
UPC
Vdiag No.: 48, 4C
AC008
COMPRESSOR CONTROL
NOTESSpecial notes:
Activating the command with the engine running is prohibited.
Check the condition and connection of fuse 22 (10A) on the Protection and Switching
Unit.
Use Wiring Diagrams Technical Note for Mégane II or Scénic II.
Check the condition and connection of the air conditioning compressor component code 171 (tabs bent, broken
or oxidised).
If the connector is faulty and there is a repair procedure (see Technical Note 6015A, Electrical wiring repair,
Wiring: Precautions for repair), repair the connector, otherwise replace the connector.
Check for earth connection code MAS on the air conditioning compressor component code 171.
If the connection is faulty and there is a repair procedure (see Technical Note 6015A, Electrical wiring repair,
Wiring: Precautions for repair), repair the wiring, otherwise replace it.
Check for + 12 V on connection code 38R on the compressor when the command is running.
If the connection is faulty and there is a repair procedure (see Technical Note 6015A, Electrical wiring repair,
Wiring: Precautions for repair), repair the wiring, otherwise replace it.
Check the insulation, continuity and the absence of interference resistance on the following connection:
–38R, between components 1337 and 171.
If the connection is faulty and there is a repair procedure (see Technical Note 6015A, Electrical wiring repair,
Wiring: Precautions for repair), repair the wiring, otherwise replace it.
If the fault is still present, contact Techline.
AFTER REPAIRRepeat the conformity check from the start.

ENGINE COMPARTMENT CONNECTION UNIT
Fault finding - Interpretation of commands87G
87G - 87V7 MR-372-J84-87G050$770.mif
UPC
Vdiag No.: 48, 4C
AC014
ALTERNATOR REGULATION
NOTESConditions for the application of the command:
–engine running at idling speed and warm engine,
–air conditioning off,
–check that the passenger compartment blower unit is not operating.
–check that the cooling fan assemblies are not operating,
–if fault DF007 UPC-alternator connection is declared present, deal with this fault
first,
–check the conformity of PR010 Alternator charge (see Interpretation of
parameters).
Effect of command:
–for 30 seconds, the Protection and Switching Unit sets the alternator a regulation
voltage of 15 V ± 0.5,
–then for another 30 seconds, the Protection and Switching Unit imposes a
regulation voltage of 13 V ± 0.5 on the alternator.
Switch off all the electrical consumers (fans, main beam headlights, etc.).
Measure the voltage across the alternator terminals, between the B+ terminal and the alternator chassis earth.
Run AC014 Alternator regulation.
Wait 20 seconds,
For 10 seconds the alternator voltage should be 15 V ± 0.5.
Wait 20 seconds,
For 10 seconds the alternator voltage should be 13 V ± 0.5.
Switch on the heated rear screen and the main beam headlights.
Run AC014 again.
Wait 20 seconds,
For 10 seconds the alternator voltage should be 15 V ± 0.5.
Wait 20 seconds,
For 10 seconds the alternator voltage should be 13 V ± 0.5.
If the values obtained are not correct, replace the alternator (see MR 364 or MR 370 Mechanical, 16A, Starting-
Charging, Alternator: Removal - Refitting).
AFTER REPAIRRepeat the conformity check from the start.