Midco International Inc.
11
8471 15
MADE
in the
USA
Trouble Chart
Make sure the thermostat and operating controls are calling for heat. Defective wiring or loose
connections can simulate the component defects outlined below. Check associated wiring before
replacing a component.
ELECTRICAL AND FLAME CHECKS MUST BE MADE IN THE ORDER LISTED
.
I.
MOTOR WILL NOT RUN
A. Confi rm 120V between strip terminals:
1.
L2
&
L1
no voltage - Fused disconnect off or Fuse open.
2.
L2
&
3
no voltage - Optional on/off and/or safety controls open.
3.
L2
&
4
no voltage - Burner Switch or Timer open and/or Remote Switch or Timer open.
4.
L2
& Thermal Switch terminal 1 (black wire).
a. None - Thermal Switch is defective.
b. Yes - Motor is defective.
II.
MOTOR RUNS CONTINUOUSLY, BUT NO FLAME- HOUSING COOL
A. Confi rm that Main Manual Shut-Off Valve is open.
B. Check for 120V between strip terminals
4
and
L2
.
1. Yes - turn Burner Switch or Timer off for a minimum, of 30 seconds to
RESET
Electronic
Control.
2. No voltage, Thermal Switch is defective.
C. Check for 24V* between strip terminals
6
to
10
. No voltage, transformer is defective.
D. Check for 24V* between strip terminals
5
and
10
. No voltage, motor interlock switch is defective.
E. Check for 24V* between Electronic Control
24 (PWR)
terminal and strip terminal
10
. 24V yellow
wire from strip terminal 10 is defective.
F. Check for 24V* between Electronic Control
24 (GND)
terminal and strip terminal
10
. No voltage,
red wire from terminal strip 5 is defective.
G. Turn burner control off for a minimum of 30 seconds to
RESET
Electronic Control for each of the
following steps.
CAUTION: Tests are valid only during the 6 second trial for ignition
.
1. Check for 24V* between Electronic Control Valve terminal and strip terminal
10
. No volt age,
Electronic Control or Fuse is defective.
2. Check for 24V* between strip terminals
7
and
10
. No voltage, blue wire from strip terminal
7
is defective.
3. Check for ignition spark (spark length approximately 1/8″):
a. Between Electronic Control HI VOLTAGE terminal and earth ground. No spark, Electronic
Control or Fuse is defective.
b. Between electrode wire and Spark Electrode. No Spark, Electrode wire is defective.
c. Check for spark between Spark Electrode and ground barrier. See Figure 5. If ignitor tip is
not visible with burner mounted, but spark can be heard, continue with Step G4. If spark cannot
be heard, refer to Section VIII IGNITOR AND REGULATOR ASSEMBLY for spark test.
4. Connect manometer to Ignitor Gas Pressures Test Tap and, during 6 second trial for ignition
period, check gas pressure.
a. No pressure, confi rm that pressure of at least 4″ W.C. is available at inlet of automatic gas
valve (connect manometer to valve upstream tap) and repeat Step G4. If still no ignitor gas
pressure, valve is defective.
b. Ignitor gas pressure 3″ to 4″ W.C., continue with Step G5.
c. .Adjust the ignitor regulator to 3.5″ W.C. while gas is fl owing.
5. Open charging door, make sure any
Door Open
interlock is bypassed, and repeat trial for
ignition.
a. With fl ame on, close charging door and check combustion chamber pressure, burner peep
hole can be used for access to obtain approximate reading. Make sure sensing tube extends
into the combustion chamber for at 6″. Pressure should be between 0″ and minus 0.5″ W.C. If
pressure is on the high negative side of the range, increase the ignitor gas pressure to 4″ or
5″ W.C.
b. No fl ame, clean and test ignitor assembly per Section VIII IGNITOR AND REGULATOR
ASSEMBLY
Trouble Shooting
