6.13 Testing Heaters
To conrm a heater is functioning properly, do the following:
1. Make sure the system is grounded correctly. Refer to Section 6.12 for more information
2. With the heater at or near room temperature, use an ohmmeter to measure the resistance
through the heater. Refer to the electrical schematic for the required ohms measurement.
The normal tolerance for all heaters is ±15%.
IMPORTANT!
A common problem with heaters is moisture absorption due to the hygroscopic nature of the
insulation. A heater with a low case to center conductor insulation reading (<10K Ω) should be
baked out and retested to determine if moisture was the cause. Contact Husky for more
information.
3.
Using an ohmmeter, measure the resistance through each lead to ground. A measurement
from either lead to ground that is below 100K Ω indicates a short to ground. A measurement
from 100K Ω to 1M Ω is often associated with a wet heater.
A measurement greater than 1M Ω is good.
NOTE:
A short reading can be the result of either a pinched wire or a broken heater element. Inspect the
wires rst to make sure there are no pinched or damaged lead wires. A heater wire can be spliced,
however, this should only be done by a certied electrician. The splice should include dual layer
heat shrink tubing with an adhesive inner layer to avoid potential water shorts. The heat shrink
should be rated for 150 °C (203 °F) minimum.
NOTE:
Refer to the electrical schematics for resistance information.
6.14 Removing and Installing the Cavity Plate
Removing the cavity plate provides access to wiring, nozzle tips, nozzle heaters and gates. The
cavity plate can be removed when the mold and hot runner assembly is in the machine or on a
work bench.
Hot Runner Installation Manual v 2.2 — March 2021 Maintenance
Testing Heaters 97
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