6
LEAKAGE TEST
1. Park the vehicle on a level surface and block or chock
the wheels. Release the parking brakes and build the
air system to full pressure.
2. Turn the engine OFF and make 4 or 5 brake applications
and note that the service brakes apply and release
promptly.
3. Build system pressure to governor cut-out and turn the
engine OFF.
Twist-Lock
Connector
(Bayonet
Connector)
Optional Adapter
Figure 7 - Exterior Views and Electrical Connections
1 2
3
1
2
3
1 2
3
1
2
3
1 2
3
1
2
3
1 2
3
1
2
3
1 2
3
1
2
3
43
41
2
42
3
1
Packard
Terminal
Name
Function
41
Source
42
Hold
43
Exhaust
Bayonet
Terminal
Name
Function
1
Exhaust
2
Source
3
Hold
Bendix
®
M-40HF
™
Modulator
Bendix
®
M-40QR
™
Modulator
Twist-Lock Connector
(Bayonet Connector)
Packard Electric
Connector
(280 Series)
4. After determining the pressure loss with the brakes
released (2 psi/minute allowed), make and hold a
full service brake application. Allow the pressure to
stabilize for one minute.
5. Begin timing pressure loss for two minutes while
watching the dash gauges for a pressure drop. The
leakage rate for the service reservoirs should not ex-
ceed four (4) psi within two minutes for a single vehicle,
six (6) psi within two minutes for a tractor/trailer, and
eight (8) psi within two minutes for a tractor with two
trailers.
6. If either circuit exceeds the leakage values above, apply
a soap solution to the exhaust port of the modulators
and any other components in the respective circuit,
then apply the service brakes.
7. The leakage at the exhaust port of most Bendix
components, including the M-40
™
modulators, should not
exceed a one-inch bubble in three seconds. If leakage
at the modulator is determined to exceed the maximum
limits, replace the modulator.
ELECTRICAL TESTS
1. Before testing the solenoid assembly of a suspect
modulator, its location on the vehicle should be
confirmed using the troubleshooting procedure for the
specific antilock controller in use. (
See the Service Data
Sheet available on the document library on bendix.com
.)
2. Proceed to the modulator in question and inspect its
wiring connector. Disconnect the connector and test the
resistance between the pins
on the modulator
.
Refer
to Figure 7.
A. HOLD to SOURCE
(41-42)
:
12V systems: Read 4.8 to 5.6 Ohms.
24V systems: Read 13.9 to 16.3 Ohms.
B. EXHAUST to SOURCE
(41-43)
:
12V systems: Read 4.8 to 5.6 Ohms.
24V systems: Read 13.9 to 16.3 Ohms.
C. Individually test the resistance of each pin to
vehicle ground and note there is NO continuity.
If the resistance readings are as shown, the wire
harness leading to the modulator may require repair or
replacement. Before attempting repair or replacement
of the wire harness, refer to the test procedures
specified for the antilock controller in use for possible
further testing that may be required to substantiate the
wire harness problem. If the resistance values are
not
as stated
, replace the modulator.