MAINTENANCE
INFORMATION
DATE :
SUBJECT :

July 2018

MI18-37
SECTION : 22 HVAC

LANG KK73.1 ELECTROMAGNETIC CLUTCH
REMOVAL & INSTALLATION - BITZER A/C
COMPRESSOR

APPLICATION
Model

Prevost coaches, from year model 2014, with the Bitzer air conditioning compressor

DESCRIPTION
In this Maintenance Information, you will find instructions and important details necessary to
perform the removal or installation of the Lang KK73.1 electromagnetic clutch, which equips the
Bitzer (model 4NFCY) air conditioning compressor.
Note: If not equipped with a Lang KK73.1 electromagnetic clutch, your Bitzer a/c compressor is equipped
with a Linnig LA16 clutch. If this is the case, you will find the installation instructions on the document
Linnig LA16 Electromagnetic Clutch_142.254 available on the Prevost Technical Publications site, under
SUPPLIER PUBLICATIONS.

Writer:

EL

MI18-37
Page 2 / 14

CONTENT

PROCEDURE

3

LANG KK73 CLUTCH IDENTIFICATION

3

CLUTCH SECTION VIEW

4

REMOVING THE ROTOR

5

REMOVING THE BELTS
M12 MOUNTING SCREW REMOVAL
EXTRACTOR TOOL
PULLING OFF THE ROTOR
REMOVING THE COIL

5
5
5
6
6

MOUNTING THE CLUTCH ON THE COMPRESSOR

7

PREPARATION
INSTALLING THE COIL
PROPER WOODRUFF KEY POSITION
SLIPING THE ROTOR
FASTENING THE ROTOR

7
7
8
8
9

REINSTALLING THE BELTS

10

TROUBLESHOOTING, POSSIBLE DEFECTS, ELIMINATION

11

SUPPLEMENT

13

HOW TO INSTALL A NEW “CLIP-ON” UNLOADER COIL

13

Writer:

EL

MI18-37
Page 3 / 14

PROCEDURE
DANGER
Park vehicle safely, apply parking brake, stop the engine. Prior to working on the vehicle, set the
ignition switch to the OFF position and trip the main circuit breakers equipped with a trip button. On
Commuter type vehicles, set the battery master switch (master cut-out) to the OFF position.

LANG KK73 CLUTCH IDENTIFICATION

Figure 1: "LANG" & "WWW.EALANG.COM" ENGRAVED ON THE HUB

Writer:

EL

MI18-37
Page 4 / 14

CLUTCH SECTION VIEW
1233a 45678-

coil
rotor
M12 mounting screw
straining washer
bearing
M8 screw (4x)
flange
shaft end
woodruff key

COLOR CODE
rotor assembly
compressor body
Working gap must be: 0.024 in to 0.035 in
0.60 mm to 0.90 mm
Figure 2: CLUTCH SECTION VIEW

Writer:

EL

MI18-37
Page 5 / 14

REMOVING THE ROTOR

REMOVING THE BELTS

to

1) Remove the two drive belts.

M12 MOUNTING SCREW REMOVAL

2) While holding the hexagonal part of the
rotor with a wrench, loosen and remove
the M12 mounting screw (3, Figure 2).

EXTRACTOR TOOL

3) Screw extractor tool #680888 in the
straining washer (3a, Figure 2).
Do not use a standard M16 screws unless
the tip of it has been rounded off, failing to
do so may damage the shaft end bore or
threads where the M12 screw is fastened

Writer:

EL

EXTRACTOR TOOL # 680888

MI18-37
Page 6 / 14

PULLING OFF THE ROTOR
4) Pull off the rotor with the extractor tool.
Due to the back pressure, the rotor
detaches from the shaft end (7, Figure 2)
of the compressor.
DO NOT USE AN IMPACT WRENCH

PULL OFF THE ROTOR

TAKE OFF THE ROTOR

REMOVING THE COIL

5) Loosen the coil M8 fastening screws (5,
Figure 2) and pull the coil off the.

Writer:

EL

MI18-37
Page 7 / 14

MOUNTING THE CLUTCH ON THE COMPRESSOR

PREPARATION

1) The flange and the shaft end must be free
from dirt.

2) Apply
high
temperature
approved
assembly grease on the shaft end for easy
dismounting of the clutch.
Use of Molykote G-rapid-plus or Molykote
P 40 is recommended

INSTALLING THE COIL

3) Reinstall the coil. Slip the coil on the
compressor flange. The cable connector
must be positioned on the right side as
shown on the image.

PROPER CABLE CONNECTOR POSITION

4) Fasten the four M8 screws by hand to the
compressor and then apply final torque.
Coil mounting screws: 22 lbf-ft (30 N-m).
Use blue Loctite 243.
Caution: Pay attention to the precise seat of
the coil. A non-observance may cause the
destruction of the clutch components during
operation.

Writer:

EL

MI18-37
Page 8 / 14

PROPER WOODRUFF KEY POSITION

5) To avoid damaging the rotor bore, make
sure that the woodruff key is positioned as
shown on the image at right, otherwise, it
could move when the rotor is inserted on
the shaft end.

SLIPPING THE ROTOR

6) Carefully mount the rotor on the shaft end
by hand.
Never use a hammer for pressing the rotor on.
To avoid damaging the bore of the rotor, feel
the engagement of the key in the keyway and
slip the rotor on the shaft end of the
compressor till reaching the stop.

Writer:

EL

MI18-37
Page 9 / 14

FASTENING THE ROTOR

7) Fasten the rotor to the shaft end by using
the M12 screw and holding-up with a
wrench on the hexagonal part of the rotor.
Rotor mounting screw: 60 lbf-ft (81 Nm)
Use blue Loctite 243.
Turn rotor by hand and pay attention to the
free run and the generation of noises. In case
of rubbing, grinding or similar noises, dismount
the rotor and check installation.

8) Once properly tighten, apply a torque seal
mark.

During cleaning or other work on the
compressor, the clutch must be covered to
prevent the penetration of greasy liquids,
grease or dirt particles in the working gap (see
figure 2) of the clutch. No high pressure
cleaning.
Working gap must be: 0.024 in - 0.035 in
0.60 mm - 0.90 mm

Writer:

EL

MI18-37
Page 10 / 14

REINSTALLING THE BELTS
1. Reinstall the drive belts.
A belt strand tension gage is needed
On vehicles not equipped with an auxiliary
alternator (i.e. 2 identical belts), belt
tension should be within this range:
90-100 lbs new belts (mean of 2 belt
values)
75-85 lbs used belts (mean of 2 belt
values)
On vehicles equipped with an auxiliary
alternator (i.e. 2 different belts), belt
tension should be within this range:
A belt strand tension gage is needed
150-160 lbs new belts (mean of 2 belt
values)
120-130 lbs used belts (mean of 2 belt
values)
Apply loctite on bolt (B) and hand tighten.
Adjust belt tension using bolt (A). Use the
jam nut to prevent rotation of bolt (A).
When proper tension is achieved, tighten
bolt (B) to 43 lbf-ft. (58 N-m).

Writer:

EL

MI18-37
Page 11 / 14

TROUBLESHOOTING, POSSIBLE DEFECTS, ELIMINATION
PROBLEM

CAUSE

SOLUTION

Clutch does not close any more,
no current stream

Intermittent contact in the plug

Check plug

Contact corroded

Clean contact

Connection cable defect

Repair cable, replace coil

Insufficient voltage supply

Check supply voltage

Impurities in the working gap
(foreign matters)

Disassemble clutch, remove
foreign matters and assemble it
again

Insufficient voltage supply

Check power supply

Friction surface polluted by small
quantities
of
greasy/oily
substances

Disassemble clutch, clean friction
surfaces with alcohol and
assemble it again.

Heat penetration in the clutch by
slipping V-belts thus grease
penetration in the bearing or
overheating of the clutch

Disassemble
clutch.
Clean
friction surfaces or replace
already damaged components.
After reassembly of the clutch,
tension V-belts correctly

Incorrect distance between coil
and rotor (coil not in line with the
rotor), thus the switchable torque
is reduced

Disassemble clutch, check cone
for cleanness. Check the seat of
the feather key, check the seat of
the coil.

Clutch worn, working gap too big
(app. 1,2 mm), friction partner
blue

Replace clutch or component

Clutch
does
not
open
immediately when switched off,
this will cause a premature wear
of the clutch), shrieking noise

Voltage supply not completely
interrupted

Check
circuit
element
for
switching the coil ON/OFF and
replace it if necessary

Clutch does not open any more,
voltage supply is in order

Clutch worn and friction partners
welded to each other on the
friction surface

Replace clutch

Permanent grinding noise

Coil not correctly centered or not
firmly screwed down

Check coil, screw it down, or
replace it if damaged. Check
clutch
for
consequential
damages,
eventually
disassemble
clutch,
check
bearing and friction surfaces,
replace eventually damaged
components.

Compressor bearings defect,
causes friction between coil and
rotor.

Replace bearings. Check coil
function. Replace it if damaged.
If clutch slips, replace whole
clutch due to friction damage.

Clutch does not close in spite of
current stream

Clutch slips when switched on
(causes the destruction of the
clutch by premature wear),

Writer:

EL

MI18-37
Page 12 / 14

Friction surface polluted
greasy or oily substances

Untrue run of the pulley, loud
running noise.

Writer:

EL

by

Disassemble the clutch, replace
bearing, if necessary, clean
friction surfaces with alcohol and
assemble them again.

Blockade of the compressor.
Clutch slips, both components
blue due to friction heating.

Clutch destroyed, replace it.

Bearing damaged due to wear or
incorrect seat of the feather key.

Check whether feather key and
groove are flushing. If not,
change
clutch
as
the
components will be permanently
damaged, or disassemble the
clutch and replace bearing.

MI18-37
Page 13 / 14

SUPPLEMENT
HOW TO INSTALL A NEW “CLIP-ON” UNLOADER COIL
1. Loosen the screw securing the connector
to the coil and then unplug the connector
(A). Keep the screw and the connector
rubber gasket for later use.
2. Unscrew the aluminum cap and discard.
3. Remove the plastic capture nut and
discard.
4. Remove the coil and discard
5. Keep the O-ring on the stem.

6. Install the new clip-on coil on the stem.
7. Slide the coil over the stem assembly with
the O-ring at the base of the stem.

Writer:

EL

MI18-37
Page 14 / 14

PARTS / WASTE DISPOSAL
Discard according to applicable environmental regulations (Municipal/State[Prov.]/ Federal)

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Writer:

EL