Detroit Radiant Products Company DES3 Series - Manual (Page 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.
15
DES3 Series 4.0 Troubleshooting Guide
Key
Start
Question
Process
Question
Corrective
Action
Correct wiring or
replace relay.
The blower is faulty and
must be replaced.
Is there 120VAC
coming to the fan?
Yes
Is the inlet or outlet of the
unit obstructed? i.e. ice,
birds nest, dirt, etc.
Check for loose wiring or
restrictions in hose connections
to the pressure switch. Are they
ok?
Remove obstruction.
No
Yes
No
Repair wiring or hose
connections.
No
The heater is equipped with a safety differential pressure
switch. The switch is a normally open switch and is
located in the air chamber. Temporarily place a jumper
across the terminal of the switch. Does the igniter spark?
Yes
Yes
While the switch is
temporarily bypassed,
check for 120VAC from
the switch to the circuit
board. Does 120VAC
enter the circuit board?
No
Replace circuit
board.
Faulty
wiring.
Repair or
replace
wiring.
Yes
No
*
*
Replace the pressure switch after verifying the
following:
• Baffle(s) is in the tube farthest from the burner.
• Heater, blower, squirrel cage, intake and exhaust are
clean and free from dirt and obstructions.
• The 4 in. air intake pipe does not exceed 20 ft.
and/or two elbows.
• There is not a negative pressure experienced
at the area of air intake (i.e. attic space, high
winds, very tight buildings, etc.).
If any of the above were occurring, please address the
problem.