Mercedes-Benz Sprinter / Dodge Sprinter. Manual — part 502

OPERATION

The compressor clutch components provide the

means to engage and disengage the compressor from
the engine serpentine accessory drive belt. When the
clutch coil is energized, it magnetically draws the
clutch into contact with the pulley and drives the
compressor shaft. When the coil is not energized, the
pulley freewheels on the clutch hub bearing, which is
part of the pulley.

The compressor clutch engagement is controlled by

several components:

• A/C switch on the A/C-heater control panel
• Evaporator temperature sensor
• A/C pressure transducer
• Air temperature sensor
• CAN bus messages
The compressor clutch is de-energized under any of

the following conditions:

• Blocked compressor (thermal fuse in the pulley)
• Low pressure in the system
• Low evaporator temperature
• Hard acceleration (WOT)
• High coolant temperatures

STANDARD PROCEDURE

A / C COMPRESSOR CLUTCH AIR GAP

If a new clutch plate and/or clutch pulley are being

used, the air gap between the clutch plate and clutch
pulley must be checked using the following proce-
dure:

(1) Using feeler gauges, measure the air gap

between the clutch plate and the clutch pulley fric-
tion surfaces.

(2) If the air gap is not between specifications

(Refer to 24 - HEATING & AIR CONDITIONING -
SPECIFICATIONS), add or subtract shims until the
desired air gap is obtained.

NOTE: The shims may compress after tightening
the compressor shaft bolt. Check the air gap in four
or more places on the clutch plate to verify that the
air gap is still correct. Spin the clutch pulley before
making the final air gap check.

A / C COMPRESSOR CLUTCH BREAK - IN

After a new compressor clutch has been installed,

cycle the compressor clutch approximately twenty
times (five seconds on, then five seconds off). During
this procedure, set the heater-A/C control in the
Recirculation Mode, the A/C button in the on posi-
tion, the blower motor switch in the highest speed
position, and the engine speed at 1500 to 2000 rpm.
This procedure (burnishing) will seat the opposing
friction surfaces and provide a higher compressor
clutch torque capability.

REMOVAL

The refrigerant system can remain fully-charged

during compressor clutch, pulley, or coil replacement.
The compressor clutch can be serviced in the vehicle.

(1) Disconnect and isolate the battery negative

cable.

(2) Remove the serpentine drive belt (Refer to 7 -

COOLING/ACCESSORY

DRIVE/DRIVE

BELTS

-

REMOVAL).

(3) Disconnect the engine wire harness connector

for the compressor clutch coil from the clutch coil
wire harness connector on the top of the compressor.

(4) Remove the retainer securing the compressor

clutch coil lead on the top of the compressor.

(5) Remove the bolt that secures the compressor

clutch to the compressor shaft (Fig. 2). If necessary, a
band-type oil filter wrench or strap wrench can be
placed around the clutch plate to aid in bolt
removal.

Fig. 1 A/C Compressor Clutch

1 - BOLT
2 - CLUTCH PLATE
3 - PULLEY AND BEARING
4 - FIELD COIL
5 - SNAP RING
6 - SNAP RING
7 - SHIM (2)

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(6) Tap the clutch plate lightly with a plastic mal-

let to release it from the splines on the compressor
shaft. Remove the clutch plate and shim(s) from the
compressor shaft (Fig. 3). Be certain not to lose
the shim or shims.

CAUTION: Do not pry between the clutch plate and
the pulley to remove it from the compressor shaft.
Prying may damage the clutch plate.

(7) Using snap ring pliers (Special Tool C-4574 or

equivalent), remove the external snap ring that
secures the compressor clutch pulley to the front of
the compressor, then slide the pulley off of the com-
pressor (Fig. 4).

(8) Remove the screw that secures the clutch coil

wire harness connector bracket and ground clip to
the top of the compressor housing.

(9) Using snap ring pliers (Special Tool C-4574 or

equivalent), remove the external snap ring that
secures the compressor clutch coil to the front of the
compressor, then slide the clutch coil off of the com-
pressor (Fig. 5).

Fig. 2 Compressor Shaft Bolt and Clutch Plate

1 - COMPRESSOR CLUTCH PLATE
2 - COMPRESSOR SHAFT BOLT

Fig. 3 Clutch Plate And Shim(s)

1 - COMPRESSOR SHAFT
2 - CLUTCH PLATE
3 - CLUTCH PLATE SHIM

Fig. 4 Pulley Snap Ring

1 - SNAP RING

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INSPECTION

Compressor clutch components should always be

inspected closely before they are reinstalled. The
clutch plate and clutch pulley are mated at the fac-
tory using a burnishing operation. No attempt should
be made to separately replace the compressor clutch
pulley or clutch plate. The clutch coil may be serviced
separately.

(1) Examine the friction surfaces of the clutch pul-

ley and the clutch plate for wear. The clutch pulley
and clutch plate should be replaced if there is exces-
sive wear or scoring.

(2) Examine the friction surfaces of the clutch pul-

ley and the clutch plate for oil contamination. If the
friction surfaces are oily, the clutch pulley and clutch
plate should be replaced. Also inspect the shaft and
nose area of the compressor for oil. Remove the felt
packing from around the compressor shaft in the
compressor front cover. If the felt is saturated with
oil, the compressor front shaft seal is leaking and the
compressor will also have to be replaced.

(3) Check the clutch pulley bearing for roughness

or excessive leakage of grease. Replace the clutch
pulley and clutch plate if the bearing is faulty.

INSTALLATION

(1) Align the dowel pin on the back of the clutch

field coil with the hole in the compressor front cover,
and position the clutch coil onto the compressor. Be
certain that the cluch coil wire harness leads are
properly oriented and routed so that they are not

pinched between the compressor front cover and the
clutch coil.

NOTE: A new snap ring must be used to secure the
clutch coil to the compressor. The bevel side of the
snap ring must face outward.

(2) Using snap ring pliers (Special Tool C-4574 or

equivalent), install the external snap ring that
secures the clutch coil to the front cover of the com-
pressor. The bevel side of the snap ring must be fac-
ing outward and both snap ring eyelets must be
oriented to the right or left of the clutch coil dowel
pin on the compressor. Be certain that the snap ring
is fully and properly seated in the groove.

CAUTION: If the snap ring is not fully seated in the
groove it will vibrate out, resulting in a clutch fail-
ure and severe damage to the compressor front
cover.

(3) Install and tighten the screw that secures the

clutch coil wire harness connector bracket and
ground clip to the top of the compressor housing.

(4) Install the pulley onto the front of the compres-

sor. If necessary, place a block of wood on the friction
surface and tap gently with a hammer (Fig. 6).

CAUTION: Do not mar the friction surfaces of the
pulley.

(5) Using snap ring pliers (Special Tool C-4574 or

equivalent), install the external snap ring (bevel side
facing outward) that secures the clutch pulley to the

Fig. 5 Clutch Coil Snap Ring

1 - SNAP RING PLIERS
2 - CLUTCH COIL
3 - SNAP RING
4 - COMPRESSOR

Fig. 6 Pulley Assembly Install

1 - PULLEY ASSEMBLY
2 - WOOD BLOCK

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front cover of the compressor. Be certain that the
snap ring is properly fully and properly seated in the
groove.

(6) If the original clutch plate and clutch pulley

are to be reused, reinstall the original shim(s) on the
compressor shaft against the shoulder. If a new
clutch plate and/or clutch pulley are being used,
install a trial stack of shims 1.0 mm (0.040 in.) thick
on the compressor shaft against the shoulder.

(7) Install the clutch plate onto the compressor

shaft.

(8) Install and tighten the compressor shaft bolt. If

necessary, a band-type oil filter wrench or a strap
wrench can be placed around the clutch plate to aid
in bolt tightening. Tighten the bolt to 17.5 N·m (155
in. lbs.).

NOTE: The shims may compress after tightening
the shaft bolt. Check the air gap in four or more
places to verify the air gap is still correct. Spin the
pulley before performing a final check of the air
gap.

(9) If a new clutch plate and/or clutch pulley are

being installed, the air gap between the clutch plate
and clutch pulley must be checked (Refer to 24 -
HEATING & AIR CONDITIONING/CONTROLS/A/C
COMPRESSOR CLUTCH - STANDARD PROCE-
DURE).

(10) Install the retainer that secures the compres-

sor clutch coil lead to the top of the compressor.

(11) Reconnect the engine wire harness connector

to the clutch coil lead on the top of the compressor.

(12) Reinstall the serpentine accessory drive belt

(Refer to 7 - COOLING/ACCESSORY DRIVE/DRIVE
BELTS - INSTALLATION).

(13) Reconnect the battery negative cable.
(14) If a new clutch plate and/or clutch pulley are

being installed, the new clutch components must be
burnished (Refer to 24 - HEATING & AIR CONDI-
TIONING/CONTROLS/A/C COMPRESSOR CLUTCH
- STANDARD PROCEDURE).

A / C COMPRESSOR CLUTCH
COIL

DIAGNOSIS AND TESTING

A / C COMPRESSOR CLUTCH COIL

The air conditioning compressor clutch coil electri-

cal circuit is controlled by the ATC control module
which is integral to the heater-A/C control. Begin
testing of a suspected compressor clutch coil problem
by performing the ATC Function Test using the
DRBIII

t scan tool.

PRELIMINARY CHECKS

(1) If no diagnostic trouble codes (DTCs) are found

in the A/C-heater control or the powertrain control
module (PCM), go to Step 2. If any DTCs are found,
repair as required.

(2) If the A/C compressor clutch still will not

engage, verify the refrigerant charge level (Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING
- DIAGNOSIS AND TESTING - REFRIGERANT
SYSTEM LEAKS). If the refrigerant charge level is
OK, go to TESTS. If the refrigerant charge level is
not OK, adjust the refrigerant charge as required.

TESTS

(1) Verify the battery state of charge (Refer to 8 -

ELECTRICAL/BATTERY

SYSTEM/BATTERY

-

DIAGNOSIS AND TESTING).

(2) Connect an ammeter (0 to 10 ampere scale

selected) in series with the clutch coil feed terminal.
Connect a voltmeter (0 to 20 volt scale selected) to
measure voltage across the battery and the clutch
coil.

(3) With the A/C-heater control in the A/C mode

and the blower motor at low speed, start the engine
and allow it to run at a normal idle speed.

(4) The A/C compressor clutch should engage

immediately, and the clutch coil supply voltage
should be within two volts of the battery voltage. If
the coil supply voltage is OK, go to Step 5. If the coil
supply voltage is not within two volts of battery volt-
age, test the clutch coil feed circuit for excessive volt-
age drop and repair as necessary.

(5) For the acceptable A/C clutch coil current draw

specifications refer to 24 - HEATING & AIR CONDI-
TIONING - SPECIFICATIONS. Specifications apply
for a work area temperature of 21° C (70° F). If volt-
age is more than 12.5 volts, add electrical loads by
turning on electrical accessories until voltage reads
below 12.5 volts.

(a) If the A/C clutch coil current reading is zero,

the coil is open and must be replaced.

(b) If the A/C clutch coil current reading is above

specifications, the coil is shorted and must be
replaced.

A / C HEATER CONTROL

DESCRIPTION

This ATC system uses a combination of electrical

and mechanical controls. These controls provide the
vehicle operator with a number of setting options to
help control the climate and comfort within the vehi-
cle.

The A/C-heater control is located on the instrument

panel inboard of the steering column and below the

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