Demco CR 108, Operator'S Manual

Page: 47 / 104

47
Malfunction Probable Cause Corrective Action
No brakes A. Source of air supply shut off at towing A. Open air line valves at rear of towing
vehicle. vehicle.
B. Air brake hose between semi-trailer and B. Examine air brake hose to make sure
towing vehicle not properly coupled. that hoses marked SERVICE and
EMERGENCY are properly connected to
the semi-trailer and towing vehicle.
C. Air reservoir drain cock open. C. Check air reservoir drain cocks on both
semi-trailer and towing vehicle.
D. To test for air leaks in the RE-6 valve. D. Replace with a new unit.
1. Apply soap suds to cover plate,
cover plate vent and exhaust port.
E. Air leakage in brake system. E. Examine all air hoses, lines, and
connecting units in the brake system for
air leaks. Replace units that are found
defective.
F. Low air pressure. F. Check air pressure gauge on towing
vehicle. Pressure must not be below 80 PSI.
G. Defective relay-emergency valve. G. Replace defective valve.
H. Brake air chamber inoperative. H. Check for punctured diaphragm.
I. Brakes need adjustment. I. Adjust brakes.
Insufficient A. Improper brake adjustment on worn A. Adjust brakes or replace brake shoe
Brakes. brake linings. assemblies as necessary.
B. Improper slack adjuster adjustment. B. Adjust slack adjuster.
C. Air leakage in brake system. C. Examine for air leaks in brake system.
replace units that are found defective.
D. Low air pressure. D. Check air pressure gauge in towing
vehicle cab. Pressure must not be below
80 PSI.
E. Restriction in air hose or lines. E. Look for dented or kinked airlines.
Examine air hose to make sure it is not
pinched between other units on the same
trailer.
Troubleshooting
Wheels, Hubs, Bearings, And Tires
(Continued)