Detroit Radiant Products Company HL3 Series - Manual (Page 15)

15
NOTICE Bypassing any switch is intended for testing purposes only. Do not leave switch bypassed
during normal operation or the heater’s built-in safety mechanisms will be compromised.
* Refer to LED diagnostic Fault Code Chart; p.13.
HL3 Series 4.0 Troubleshooting Guide
Is the power across
the 24V wire on the
circuit board and
ground 24V?
Is the circuit
board sending
120V to the
fan?
Is the fan
obstructed?
Remove
obstruction.
Is the pressure
switch stuck in the
closed position?
Replace
switch.
Yes
Yes
Is there 120V on the
primary side of the
internal transformer?
The relay board is faulty
and must be replaced.
The circuit board is
faulty and must be
replaced.
Repair wiring between
power in and transformer. The fan is faulty and must be replaced.
The internal
transformer is
faulty and must
be replaced.
Is the power across
the t-stat wire on the
circuit board and
ground 24V?
Yes
No No
Yes Yes
No
No
Yes
Is the power across
the middle (low)
terminal of 24V plug
and ground (screw
on the Burner Control
Box) 24 Volts?
Repair thermostat or wiring from
thermostat to heater.
Is there 24V
across the TH and
ground terminals
on the circuit
board?
Correct wiring.
Is the circuit
board sending
120V to the
fan?
Is the fan
obstructed?
Remove
obstruction.
Is the pressure switch stuck
in the closed position?
Replace
pressure
switch
Yes Yes
Yes
Yes Yes
No
No
No
Check for loose wiring or
restrictions in hose connec-
tions to pressure switch.
Are they OK?
Replace wiring or hose connections.
*After 0-30 seconds of
non-operation has passed,
is there a flash code for
APS failure (2 flashes)?
Replace the pressure switch after verifying:
• Baffle(s) are in the radiant tube furthest from
the burner.
• Heater, fan blowers ,squirrel cage, intake and
exhaust are clean and free from dirt and
obstructions.
• The 4” air intake pipe does not exceed 20 ft.
and/or 2 elbows.
• There is not a negative pressure experienced
at the area of air intake (e.g.; high winds, attic
space, tightly sealed building).
Replace circuit board.
No
Yes Yes
No
Key
Without HLRP Isolation Relays:
Start
Question
Process
Question
Corrective
Action
With HLRP Isolation Relays:
Process
Question
Corrective
Action
No
No
No
No