Detroit Radiant Products Company LD3 Series - Manual (Page 51)

51
LD3 Series 5.0 Maintenance • Troubleshooting Guide
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. Continued on page 53
Is the circuit board
sending 120 VAC
to the draft inducer
motor?
Check fuse on circuit board and
internal controls transformer.
Yes
Is there 24
VAC across
the ‘R’ and ‘C’
terminals?
Is there 24
VAC across
the ‘W’ and ‘C’
terminals?
Yes
After approximately 10
seconds of operation,
is there a flash code for
Pressure Switch Failure?
No
Replace pressure switch
after verifying:
• Heater, blower, and
venting are clean and
free of obstructions.
• The allowable vent
length is not exceeded.
• There is not a negative
pressure experienced
at the area of intake
(e.g., high winds, attic
space, tightly sealed
building).
No
Repair thermostat or
thermostat wiring.
Yes
Remove obstruction.
Is the draft inducer
impeller obstructed
or locked up?
Yes
Is the pressure
switch stuck in the
closed position?
No
The draft inducer motor is
faulty and must be replaced.
Replace
circuit board.
Monitor the voltage on the gas valve
terminals during trial for ignition. Is
there 24 VAC present during the
ignition sequence?
Yes
Pressure switch is
faulty.
Replace circuit board.
No
NOTICE
Yes
No
Check for loose wiring
or restrictions in hose
connections to pressure
switch. Are the OK?
No
Replace wiring or
hose connections.
Gas valve is faulty. Replace. Yes
Check for flash codes on the circuit board.
Replace the ignition module.
No
Yes *After 10-12 seconds of non-operation
has passed, is there a flash code for
APS failure (2 or 3 flashes)?
Replace circuit board. No
Yes
No