Manual

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