10
Danfoss T-420 Crimp machine operator´s manual December 2022
Troubleshooting procedures
T-421U and T-421U-110 Electric pump
PROBLEM
CAUSE
SOLUTION
Pump/motor does not start
Blown fuse; Improper electrical hookup
(cut cord, loose wire, switch malfunc-
tions)
Step #1
Motor starts but blows fuses
High Amps; Pusher doesn’t advance;
Pump binding or scored; Cold oil
Step #1
Replace pump
Motor runs - Pusher does not advance
Shuttle stuck open; Pump coupling
sheared; Pump unload valve stuck open
Step #4
Replace pump
Motor runs - Pusher advances but
doesn’t develop final crimp pressure,
blows fuse
Pump unload valve stuck shut
Replace pump
Motor runs - Pusher advances but
doesn’t develop final crimp pressure
Relief valve leaking;
Shuttle valve leaking;
Relief valve set low
Step #3
Step #4
Step #5
Pusher won’t retract
Shuttle valve stuck closed
Step #4
Erratic Pusher movement
Low oil level
Worn Seal
Step #2
Replace pump
Noisy Pump: On start up only
(continuous)
Low room temp - oil too thick
Air leaking - low oil level
Use lighter weight oil
Step #2
Oil temperature hot
Having unit operate at crimping
PSI too long
Low oil level;
Pump worn (longer cycle time)
Leaking RV, shuttle valve
Operate for 3 seconds at crimp pressure
Step #2
Replace Pump
Step #3, #4
Troubleshooting T-421U and T-421U-110 Electric Pumps
(For steps please refer to page 9)
Summary of Contents for T-420
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