UNIT TROUBLESHOOTING - CONTINUED
TEST OR INSPECTION
6. HAND PARKING BRAKE DRAGS - CONTINUED
Step 2. Check parking brake air supply (in emergency air reservoir) and air hoses between
parking brake lever and spring brakes on rear wheels.
If air hoses or parking brake air supply components are defective, replace
hoses and/or components (page 4-126).
If air hoses and parking brake air supply components are not damaged or
leaking, go to step 3.
Step 3. Check that spring brake is completely released (page 4-93).
If spring brake is not completely released, manually release spring brake
as per data plate on rear platform. If spring brake cannot be released
manually, replace spring brake unit.
If spring brake is completely released, refer to page 4-79 for additional
brake system information.
7. BRAKES WILL NOT RELEASE - BOTH DOLLIES
Step 1. Ensure that dolly set has not become separated from towing vehicle and that air
brake supply line to the front dolly air reservoir (4) and the rear dolly air reservoir (5)
is not disconnected or ruptured.
Make proper air brake line connection to tow vehicle as applicable.
Repair/replace disconnected/ruptured air brake hoses/connection (page 4-
Step 2. Attempt to release brakes with auxiliary brake control valve on front dolly (1), or on
rear dolly (2).
Step 3. Check that parking brake ON/OFF lever (3) on rear dolly is not at ON position.
Step 4. Check for bad emergency relay valve (6) on front dolly and (7) on rear dolly.
Loosen service brake air line (8) on emergency relay valves (6) and (7). If air
escapes and brakes release, replace emergency relay valve. If brakes dont
release, repair restriction in service brake line (8) to brake chamber tee (9).