Detroit Radiant Products Company HL3 Series - Manual (Page 14)

14
Does the heater have HLRP isolation
relays? (identified with orange
crescent around the terminal plug).
HL3 Series 4.0 Troubleshooting Guide
4.0 Troubleshooting Guide
Turn up thermostat.
Does the fan
blower turn on?
Is the power at the
heater 120V?
Find the source of the electrical problem between panel and heater.
No
Find the source of the
electrical problem
between panel and
external transformer.
Is there 120V on the
primary side of the
external transformer?
Is there 24 Volts from the
thermostat?
External transformer
is faulty and must be
replaced.
The thermostat or wiring
is faulty and should be
replaced or repaired.
Find source of electrical problem between
the external transformer and thermostat.
Is there 24V on the
secondary side of the
external transformer?
Is there 24V
to the
thermostat?
Yes
Yes
No Yes No
No Yes
Yes
No
Is the power
across the left
terminal of the
24V plug and
ground 24 Volts?
Is there 120V on
the primary side
of the internal
transformer?
Is there 24V
on the second-
ary side of the
transformer?
Replace transformer.
Repair the wiring
between the
transformer and
the 24V
terminal plug.
Repair the wiring between
power in and transformer.
Yes
No
Yes No
No
Yes
Yes
Does the igniter
warm up and
glow red?
Is the igniter
physically
damaged?
Replace igniter.
Check voltage at igniter
sequence (usually 5 to 15
seconds after power to
heater). Is it 120V?
Is the resistance through
the igniter 50-400 Ω?
Is the inlet or the outlet
of the unit plugged or
obstructed?
Remove obstruction.
No
Yes Yes
No No No
Yes
Yes
No
Continued on page 16
No
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Does the switch
light energize?
Yes
No
Is the green light burnt out?
If so, replace.
No
No
Is the inlet or the outlet
of the unit plugged or
obstructed?
No
No
Yes