UNIT TROUBLESHOOTING - CONTINUED
TEST OR INSPECTION
8. SERVICE BRAKES DO NOT HOLD SUFFICIENTLY ON FRONT AND REAR DOLLIES -
Step 2. Check service brake air system up to the emergency relay valve.
Loosen emergency air line (3) slightly at the emergency relay valve ((4) on
front dolly and/or (5) on rear dolly). If air escapes, tighten line (3) and go
on to (b). If no air escapes, replace restricted emergency air line (6).
Loosen service air line (7) slightly at the emergency relay valve. Apply
brakes on towing vehicle. If air escapes from line (7), tighten and go to
step 3. If no air escapes, replace restricted service air brake line (7).
Step 3. Check emergency relay valve.
Loosen air line (8) to brake chamber (9) slightly at the emergency relay valve (4)
or (5) for each brake (one at a time). Apply brakes on towing vehicle. If air
escapes, replace restricted brake chamber line (8). If no air escapes, replace
the emergency relay valve (page 4-131).
Step 4. Check adjustment of brakes.
Adjust brakes as necessary (page 4-119)