23
TROUBLE SHOOTING
If a hoist ever exhibits any sign of erratic operation, or load control difficulties (i.e. load creeping or chattering),
appropriate trouble shooting tests should be performed immediately. Continued operation in this manner may
result in property damage, serious personal injury or death.
A
The hoist will not lower
the load, or will not
lower the load smoothly.
1. The problem could be a plugged pilot
orifice in the brake valve. The pilot ori-
fice is a small pipe plug with a hole
drilled through, located under the pilot
port fitting in the brake valve "BR"
port. If it becomes plugged, it will pre-
vent the pilot pressure from the mani-
fold from opening the brake valve. If it
becomes loose, it will allow an unreg-
ulated amount of oil in to operate the
brake valve which can cause erratic
brake valve operation.
2. The static friction brake may not be
releasing as a result of a defective
brake cylinder seal.
NOTE: If the brake cylinder seal is
defective, you will typically find oil
leaking from the hoist vent plug.
3. The static friction brake will not
release as a result of damaged brake
discs.
4. The auxiliary (ABS) brake may not be
releasing due to a defective brake
cylinder seal.
Remove the pilot hose and fitting from
the brake valve, then use a 5/32 in. hex
wrench to remove the pilot orifice. The
diameter of the orifice is approximately
.020 in. (0.5 mm). Clean the orifice and
reinstall tightly, or install a new orifice
plug into the brake valve port.
Check the brake cylinder seal as follows:
A. Disconnect the swivel tee from the
brake release port. Connect a h a n d
pump with an accurate 0-2000 PSI (0-
13,800 kPa) pressure gauge and shut-
off valve to the -4 JIC fitting in the brake
release port.
B. Apply 1000 PSI (6,900 kPa) to the
brake. Close shut-off valve and let stand
for five (5) minutes.
C. If there is any loss of pressure in five
(5) minutes, the brake cylinder should be
disassembled for inspection of the seal-
ing surfaces and replacement of the
seals. Refer to "Motor Support - Brake
Cylinder Service".
Disassemble the brake to inspect the
brake discs. Check the stack-up height
as described in "Motor Support - Brake
Cylinder Service".
Check the ABS brake cylinder seal as
follows:
A. Remove the brake pilot pressure hose
from the fitting on the ABS brake hous-
ing.
B. Attach a hand pump with an accurate
0-2000 PSI (0-13,800 kPa) pressure
gauge to the ABS release port fitting.
TROUBLE
PROBABLE CAUSE
REMEDY