10
Midco
International
Inc.
8470 23
Trouble Chart
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.
A. Confi rm 120 V between strip terminals:
1.
L1
&
L2
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.
A. Confi rm that Main Manual Shut-Off Valve is open.
B. Check for 120 V 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 24 V* between strip terminals
6
to
10
. No voltage, transformer is defective.
D. Check for 24 V* between strip terminals
5
and
10
. No voltage, motor interlock switch is
defective.
E. Check for 24 V* between Electronic Control
24 (PWR)
terminal and strip terminal
10
. 24 V -
yellow wire from strip terminal
10
is defective.
F. Check for 24 V* 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 24 V* between Electronic Control Valve terminal and strip terminal 10. No
voltage, Electronic Control or Fuse is defective.
2. Check for 24 V* 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 at least 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.
I Motor Will Not
Run
II Motor Runs
Continuously,
but No Flame-
Housing Cool
