Dover HEIL LIBERTY TP1L-SM-0520, Service Manual, Page: 34 / 136

Issued May 2020
General Information Copyright 2020, Heil Environmental
Printed in the U.S.A.
General Information
28
PROXIMITY SWITCH TROUBLESHOOTING
When one or more of a unit’s functions do not operate properly and there are proximity switches in the circuits of the unit
for these functions, refer to the following table as a guide to find the problem(s).
NOTICE
Heil proximity switches have a Light Emitting Diode (LED) on the switch to indicate that the switch is sensing metal. The
light changes color when the switch senses metal. Green indicates the switch is ON. Yellow indicates the switch senses
metal. Some proximity switches only have the yellow light.
Proximity Switch Troubleshooting Table
Probable Cause Remedy
Loose or corroded electrical connections. Replace the electrical connections.
Damaged Switch
A. Cracked Ferrite core causing the fine internal
wire to break.
B. Cracked Ferrite core – but wire is not broken –
the sensitivity of switch will increase which
causes sensing distance to increase or switch
work intermittently as the temperature changes.
DO NOT strike switch to make it work.
DO NOT damage the switch when you adjust it.
DO NOT adjust switch too close to the metal it is sensing.
Voltage spikes from truck chassis electrical system
will break down the internal electronics of the
proximity switch. 1. Make sure the power source from the chassis
manufacturer is clean.
2. The body electrical system is protected from voltage
spikes.
Improper Sensing Range Adjust proximity switches to sense metal as follows:
If the controller input light stays on when a switch is
unplugged (the signal wire is ca12V DC) Check the proximity switch electrical circuits for the source of
the problem.
If proximity switch LED light is NOT ON. 1. Check the fuse relay block (Half/Packs with IFM
controllers). The fuse/relay box is located in the cab. Or
Check the in-line fuses (Side Loaders with IFM controllers).
The in-line fuses are located in the cab.
2. Unplug proximity switch.
3. Check the power wire (terminal C) for +12 VDC with a
multi-meter.
4. Check ground signal with multi-meter for continuity to
chassis ground.
5. Check the signal wire for continuity to appropriate
controller input terminal. See Service Manual.
6. If all three (3) wires are good, replace the proximity switch.