User Guide

Observed Problem: Possible Cause: Remedy:
A.
No gas ow.
1. Modulating
valve improperly
installed.
1. Install with arrow
on valve pointing in
direction of gas ow.
B.
Continuous low
re (electronics
problem).
1. Short circuit or
no voltage to the
amplier.
1. Prove the power
source by checking
for 24V AC at
amplier.
2. Open circuit
in TS194(Q)
Discharge Air
Sensor circuit or
wiring.
2. Check TS194(Q)
for open circuit.
See Temperature
Sensor Function of
Preliminary Circuit
Analysis (pg. 28).
Connect test
resistor as
described in step
2 of Preliminary
Circuit Analysis
(pg. 27) and follow
procedure outlined.
Replace TS194(Q)
if necessary.
3. Faulty MP2. 3. Perform Remedy
for Possible Cause
1 and 2 above.
If modulating
voltages are still not
obtained, MP2 may
be assumed faulty.
Replace.
C.
Continuous low
re (electronics
OK).
1. Short circuit or
open circuit in
Modulator Coil.
1. Measure resistance
across modulator
terminals with
connecting wires
detached.
Replace modulator
head if not approx
45-55 ohms for
M611 Valve, 50-65
ohms for M511
Valve and 60-80
ohms for MR212
and M411 Valves.
Field Service Checklist
19
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