Detroit Radiant Products Company MP Series - Manual (Page 23)

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 .
23
MP Series 4.0 Troubleshooting Guide
Key
Start
Question
Process
Question
Corrective
Action
Is there 90-120VAC
across the fan wire
leads?
Check modulating
controller flash codes .
Is the fan obstructed
or locked in place by a
foreign object?
No
Yes
Replace fan .
No
Yes Remove obstruction .
Re-connect igniter to
harness and check
voltage at igniter during
ignition sequence . Is it
approx . 120VAC?
Yes
Check connector pins
and wires . Repair or
replace .
Is the inlet or outlet of the
heater obstructed, or is
the vent exceeding the
recommended vent lengths?
Remove obstruction .
Is the wiring of the
pressure switch
loose, damaged or
disconnected?
No
Yes
Correct faulty wiring or
replace damaged wires .
Yes No
Is the pneumatic tubing to the
pressure switch connected and free
of kinks, damage or obstruction?
The heater is equipped with a safety
pressure switch . This is a normally
open, pneumatically operated
switch and is located in the service
compartment . TEMPORARILY place
jumper wires across the terminals of
the switch . Does the igniter warm up
and glow red?
No
Yes
Reconnect tubing,
free kinks, and remove
obstructions .
Yes Replace pressure switch .
No
Check modulating
controller flash codes .
Replace ignition module .
Correct improper
wiring .
Replace
ignition
module .
No