Troubleshooting Guide - Modine Manufacturing MRL Series Installation And Service Manual

5.0

Troubleshooting Guide

5.0 Troubleshooting Guide
Turn up thermostat.
Does the fan
No
blower turn on?
Yes
Find the source of the electrical problem between panel and heater.
Find the source of the
electrical problem
between panel, power
cord, and transformer.
Transformer is faulty
and must be replaced.
Find source of electrical problem between
the internal transformer and thermostat.
Does the green pressure
switch light illuminate?
Yes
Does the igniter
No
warm up and
glow red?
Yes
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Is the power at
Yes
the heater 120 V?
No
Is there 120 V on the
No
primary side of the
internal transformer?
Yes
Is there 24 V on
the secondary
No
side of the internal
transformer?
Is the green light burnt
No
out? If so, replace.
Is the igniter
No
physically
damaged?
Yes
No
Replace igniter.
Check the power across the
No
green and white wires of the
low voltage control cord.
Is the inline
Yes
fuse tripped?
No
Is there
No
24 V to the
thermostat?
Replace circuit board.
No
Check voltage at igniter
sequence (usually 5 to 15
seconds after power to
heater). Is it 120 V?
Yes
Is the resistance through
the igniter 50-400 Ω?
Yes
Consult factory.
30
MRL Series
Is there 24 V power?
Check control
Yes
wiring. Fix and
reset.
The thermostat
Yes or wiring is faulty
and should be
replaced or
repaired.
No
Is the inlet or the outlet
of the unit plugged or
obstructed?
Yes
Remove obstruction.
Yes
No