Troubleshooting Guide - LJ Wing WDF Operation Manual

Modulating Discharge Temperature (MDT or VDT EXPERT) Controls
Symptom
A. No Gas Flow 1. Modulating valve
with DO-2
on UC-01
energized.
B. Continuous Low 1. Short circuit or no
Fire (Electronics
Problem).
2. Jumper not connected
3. Faulty amplifi er (RE-26).
4. No output voltage on
C. Continuous Low
1. Short circuit or open
Fire (Electronics
OK).
2. Plunger missing,
D. Incorrect 1. Incorrect by-pass
Minimum Fire
Erratic or
Pulsating Flame. 2. Excessive negative
E. Continuous High 1. Open circuit in Outside
Fire (Electronics
Problem).
F. Continuous High 1. Foreign object holding
Fire (Electronics
OK). 2. Plunger jammed.
(Refer to Digital Control System User Manual for additional troubleshooting suggestions)

TROUBLESHOOTING GUIDE

Possible Cause
improperly installed.
voltage to the amplifi er
(RE-26).
across amplifi er (RE-26)
terminals 3 & 4.
UC-01.
circuit in Modulator Coil.
jammed or improperly
installed.
metering valve
adjustment.
burner pressure.
Air Temperature Sensor
(TS-01) or Discharge
Air Temperature Sensor
(TS-03) circuit or wiring.
valve open.
Portions reproduced with permission from Maxitrol
Field Test
1. Arrow on side of valve should
point in direction of gas fl ow.
1. Check for 24V AC at
amplifi er (RE-26) terminals
7 & 8.
2. Inspect.
3. Check item B1. Check
for 2-10 VDC input signal
from (UC-01) at terminals
1 & 2. Check for 0-20 VDC
output signal to gas valve at
terminals 5 & 6.
4. Check DC Voltage on AO-1.
1. Measure resistance across
modulator terminals with
connecting wires detached.
2. Inspect. Plunger should be
installed to operate freely in
solenoid sleeve.
1. See valve adjustments in
Section X.
2. Close main gas supply and
measure manifold pressure
with blower operating.
Reading should be less than
1.5" w.c. negative pressure.
1. Check Outside Air
Temperature Sensor
(TS-01) or Discharge Air
Temperature Sensor (TS-03)
for open internal circuit. See
Thermistor curve.
1. Remove bottom plate and
inspect valve and seat.
2. Inspect. Plunger should
be smooth and clean and
operate freely in solenoid
sleeve.
– 16 –
® Company
Remedy
1. Install properly.
1. Prove the power source.
2. Correct the wiring.
3. If item B1 checks out and
modulating voltages are
still not obtained, amplifi er
(RE-26) may be assumed
faulty. Replace.
4. Contact Factory.
1. Replace modulator head
if not approximately 45-55
ohms for M611 Valve and
60-80 ohms for MR212
Valve.
2. Clean or replace plunger if
necessary.
1. Adjust to proper minimum
fi re.
2. If reading is greater than 1.5"
negative pressure, check
for clogged fi lters or other
inlet air restrictions. Consult
factory for other solutions.
1. Replace Outside Air
Temperature Sensor (TS-01)
or Discharge Air Temperature
Sensor (TS-03
1. Clean seat. Clean valve or
replace if necessary.
2. Clean, or if necessary,
replace plunger.