25
Is Freeze-Stat
open?
Adjust or
Replace
Is end switch on
Motorized
Damper closed?
Adjust or
Replace
actuator
YES
YES
NO
Nothing
Happens
Is Overload
tripped on
starter?
Reset & measure FLA
of motor. Is it higher
than rating?
Adjust
or
change
Pulley
NO
NO
YES
Blower runs
but there is
no heat
Is the air flow LED
on Flame Saftey
illuminated?
Adjust pulley to
achieve proper
airflow.
NO
Is outside air cooler than
intake air thermostat
setting?
Proper
economizer
operation
YES
NO
Is High Temp.
Limit Tripped?
Reset
Is there a
Remote Panel
Installed?
Check wiring
Is Remote set to
"Heat"
Set Remote
Panel to
"Manual" and
"Heat" mode.
Refer to Flame
Safety Guide
YES
YES
YES
YES
NO
NO
NO
Burner lights but
heater stays in
Low Fire
Is there voltage on
Terminal #17
Replace
FSC
Are all valves
powered and open?
Check valve wiring
or open valves
With wires 3 & 4
removed from the
Maxitrol Amplifier, is
there 9.5K to 11K
Ohms between the
wires?
Replace
Discharge Air
Sensor
Remove Terminal #4
from the Maxitrol
Amplifier. Does the
heater go into High Fire?
Replace
Amplifier
With wires 1 & 2
removed from the
Maxitrol Amplifier, is
there 9.5K to 11K Ohms
between the wires?
Replace the
Temperature
Selector
Is there a short or open
circuit in Modulating
Valve? Should be 45-55
Ohms (60-80 on MR212)
Replace
Modulating
Valve
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
No
Burner lights but heater
stays in High Fire
Is there a jumper between
terminals 2 & 3 on the
Maxitrol Amplifier?
Install
Jumper
Is there a short circuit in
the Remote Temperature
Selector or wiring?
Repair short or
replace
Temperature
Selector
Is there an open circuit in
the Discharge Air Sensor
or wiring?
Repair Circuit or
replace the
Discharge Air
Sensor
Is Plunger in the
Modulating Valve jammed?
Inspect and clean. It
should operate freely in
the sleeve.
Foreign object holding
valve open. Remove
bottom plate and inspect
valve and seat. Clean or
replace valve.
No
No
No
No
Yes
Yes
Yes
Troubleshooting Flowcharts
Summary of Contents for Modular Direct Fired Heaters
Page 2: ......
