Frequently Asked Questions
Before troubleshooting Hot Melt Unit refer to the safety procedures in your OEM manual for that machine.
These are suggestions to maintain your equipment. Keystone Industries is not liable for any worn or damaged parts from disassembly or any injuries resulting from work performed on a hot melt unit or system. Please refer to OEM manual for safety information and specific maintenance instructions.
 WARNING: Allow only qualified personnel to perform troubleshooting.
Observe and follow all safety instructions.
Mechanical
Piston pump not pumping:
A. Check to see if unit is up to operating temperature
B. Check for system fault light
C. Check air supply going to pump
D. Check solenoid valve
E. Check shifter valve assembly
Piston pump strokes erratically:
A. Check to see if adhesive level is low
B. Check and see if adhesive is melted
C. Check pump seat(s) for
any foreign material lodged in them.
D. Check for broken o-ring on crossover tube
E. Check pressure relief valve
Gear pump not pumping:
1. Motor not running
A. Check for any fault indicators
B. Check to see if the pump ready light is on
C. Check for blown fuse
D. Check power
E. Check motor capacitor
F. Check motor control
2. Motor running but no adhesive is pumping out
A. Check to see if adhesive level is low
B. Check and see if adhesive is melted
C. Check for clogged nozzle on head
D. Check tank filters
E. Check inline head filters
F. Check coupler between the pump and motor
G. Check for broken o-ring on crossover tube
H. Check pressure regulator
I. Check pressure relief valve
J. Check temperature settings on system components
Poor adhesive flow
A. Check to see if the pump ready light is on
B. Check to see if the pump is working
C. Check air pressure
D. Check speed setting on gear pumps
E. Check temperature settings
F. Check tank filter
G. Check inline head filters
H. Check for restricted nozzles
Electrical
Tank not heating or under heating:
A. Check for system fault light
B. Check for blown fuse
C. Check the resistance on the tank heater
D. Check the resistance on the tank rtd
E. Check the triac
F. Check the overtemp thermostat
G. Check for broken or burned off wire going
to the tank heater
H. Check control boards
Hose not heating or is under heating:
A. Check for system fault light
B. Check for blown fuse
C. Check the resistance on the hose heater
D. Check the resistance on the hose rtd
E. Check for unplugged electrical connectors
F. Check wire connectors for broken or backed out pins
G. Check control boards
Head not heating or is under heating:
A. Check for system fault light
B. Check for blown fuse
C. Check the resistance on the head heater
D. Check the resistance on the head rtd
E. Check for unplugged electrical connectors
F. Check wire connectors for broken or backed out pins
G. Check control boards
Tank over heating:
A. Check for system fault light
B. Check the resistance on the tank rtd
C. Check triac
D. Check control boards
Hose over heating
A. Check for system fault light
B. Check the resistance on the hose rtd
C. Check control boards
Head over heating
A. Check the system fault light
B. Check the resistance on the head rtd
C. Check control boards
| 
