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Heat Sealer and Tunnel Troubleshooting Checklist

Issues with a heat shrink machine can be frustrating when products need to ship out. Sometimes the fix is closer than it looks. Issues can often be solved by troubleshooting with minimal tools or time. Follow this checklist to find problems with a shrink machine that is not working.

To begin, you should unplug the machine and open the interior to view fuses and electrical components. If turning the power on for testing, be sure to unplug before any interior work is attempted.

Click Here for a Printable Troubleshooting Checklist

Incoming Power

_______ The incoming power meets machine requirements (use a multimeter)

_______ The main power is coming on

_______ The sealer works, heater works, and tunnel conveyor all work

If all of these items are checked, move on to the next section. If incoming power is lower or higher than required, the wrong amperage can cause a machine not to function correctly. If the sealer, heater, or tunnel conveyor are not working, move to the next section. 


_______ Check all fuses for continuity (use a multimeter)

_______ Be sure fuse ends are making contact with fuse holder ends

Glass and ceramic fuses can look to be in working order when out. The best way to check is with a multimeter by checking continuity. Be sure all fuses are seated into the fuse holder.

Shrink machine fuses

Internal Wiring

_______ Inspect all internal wiring for burns or signs of sparking

_______ Tighten wires on contactors and relays

_______ Tighten wires connecting to sealing wires & tunnel blower motor(s)

Loose wires can cause unforeseen problems. If incoming power and fuses have been checked, inspect all wires for shorts and possible loose connections. Be sure any wires coming into contactors, relays, and sealing areas are tight. Be sure to tighten wires with the machine unplugged.


Inspect Relays and Contactors

_______ Are relays and contactors activating during operation

_______ Check continuity from each side of the contactor (use a multimeter)

_______ Check continuity from each side of the relay (use a multimeter)

Contactors and relays activate different parts of shrink sealers and tunnels. A contactor will engage when the heater in a shrink tunnel turns on. Relays and contactors also engage when a sealing wire is activated. Be sure all are working properly and engaging when needed.

Shrink machine contactors


This checklist will not be able to find all shrink wrap machine problems but will help find several that can be quickly solved. Be sure to have all power unplugged from the machine when touching internal parts and wires.

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