Weil-McLain 4 Series Manual page 29

Universal control systems — Control supplement
Troubleshooting
CHART 2: NO SPARK — System does not work — With vent damper
Secure connections.
Check for loose wire connections
or bad relay on transformer.
Check for open thermostat or circ. relay (where used) or check for
loose wire connections, defective spill switch or rollout thermal fuse
element, or open LWCO or high limit contacts.
If LWCO, spill switch or rollout thermal fuse element
contacts are open, determine cause and correct
condition. Failure to do so will cause severe personal injury, death,
or substantial property damage.
Is 24VAC present across terminals PV
and MV/PV?
No
Check continuity of each wire in wiring
harness to damper. Does continuity exist
for each wire?
No
Remove damper harness from boiler
Replace damper
wiring harness. TEMPORARILY install
wiring harness.
jumper between terminal 2 and
terminal 5 on damper plug in boiler
wiring harness. See Figure 14. Does
boiler fire?
Replace ignition control.
1 2
4 5
FIGURE 14
Part Number 550-110-646/0607
continued
Is damper harness securely plugged in at both
ends?
No
Check for out of round stack section.
Does motor rotate open?
Replace actuator.
Open thermostat contacts for 30
seconds. Damper will rotate to closed
position. Close thermostat contacts.
Damper will rotate to open position.
Yes
Yes
No Yes
Replace actuator.
3 Replace pilot assembly.
6
Yes
Is 24VAC present across terminals C and Y on
transformer?
No
Is 24VAC present across terminal C and yellow wire
between damper connector and rollout thermal fuse
element?
No
No Yes
Is spark present now?
Yes No
Re-test.
Securely connect and
turn ON supply voltage.
Re-test.
Replace pilot assembly.
Is spark gap 0.125" and
located in pilot gas stream?
No Yes
Replace ignition
control.
Yes
Yes
Is damper rotated open?
No Yes
Is 24VAC present at Terminals
PV and MV/PV?
No Yes
Turn OFF supply voltage.
Check spark wire. Is it securely
connected to ignition control?
No Yes
Is condition of spark
wire good (not brittle,
burned, or cracked)?
No Yes
Is spark electrode ceramic
cracked?
No Yes
Replace pilot assembly.
Turn ON supply voltage
and operate system
several complete cycles.