Build up pressure in air system using the air
compressor to cycle several times.
Check and compare the temperature at the inlet
accomplished by holding your hand on each of
the port areas.
The inlet port be very warm and The
inlet port may be very warm and a burn
The inlet port should be warmer than the outlet
port; the outlet port should be at or slightly above
ambient temperature. Since the vehicle is
stationary, the unit will become warmer than
normally experienced during over the road
operation. If both inlet and outlet temperatures
are high or at the same temperature (about 660
C or 1500 F) the deflector will need servicing.
Hold a clean shop towel under the unloader
(exhaust) port and make the air compressor go
through several "unload" cycles. Catch water
from the unloader port. If water is oily, the
compressor should be checked. If water is
"brownish" or if brown particles are expelled, the
deflector requires servicing.
After the heat exchanger has "exhausted" and
while the air compressor is in "stand-by" mode,
hold your hand under the unloader port. If air
flows out the port, the check valve at the top
(outlet port) of the heat exchanger is stuck open
and requires service, or the compressor inlet is
connected to the outlet side of the turbocharger.
If air leaks past the exhaust port while the
compressor is building up pressure, the unloader
valve is stuck open and requires attention.
While the air compressor is building up pressure,
it is normal for the check valve to produce a
rattling sound through rapid opening and closing.
When the air compressor is rebuilt or replaced or
if the heat exchanger is moved from one vehicle
to another it is recommended that the heat
exchanger unit be completely disassembled and
If the unloader valve should stick in the open position
while the vehicle is on the road, the air system
can be restored by threading a pipe plug into the exhaust
port. By doing this, the air system pressure can be
restored but moisture, etc. cannot be exhausted from the
air dryer. The unit should be serviced as soon as
possible by repairing the unloader valve.
DISASSEMBLY AND REASSEMBLY
Before any work is accomplished, it is important for
your safety and the cleanliness of your system to adhere
to the following:
The area surrounding the unit, and the unit itself,
should be thoroughly cleaned to remove dirt, oil
and other road grime.
Set parking brake.
Relieve ALL AIR from vehicles air system.
Relieve pressure in line from "UNL" port of
compressor governor to unloader port in the
center of the large nut on the bottom of the unit.
Each part of the heat exchanger can be serviced
by means of using the various service and
replacement kits available.
Servicing Unloader Valve
There are several indications which may mean that
the unloader valve of your heat exchanger unit needs
The compressor goes into "stand-by" mode but
compressor is attempting to build up pressure in
the air system.
The unit does not "unload" when compressor
goes into stand-by mode.
conditions. Check the TROUBLE SHOOTING GUIDE to
make sure that the probable cause is a malfunctioning
unloader valve on the CR BRAKEMASTER unit. If, the
probable cause is the unloader valve, it could mean that
a piece of debris is clogging this valve, and it only needs
to be cleaned, or that the valve assembly itself has been
worn and needs to be replaced. In either case, the
following steps should be taken. Refer to Fig. 24 for
numbers in parenthesis.
Disconnect electrical wire to heater.
Disconnect inlet air line from bottom cap.
CTS-4079 - CHAPTER XIV - Page 13