M-Series Technical Manual
99
Cambridge Air Solutions
TROUBLESHOOTING GUIDE
Problem
Possible Cause
Corrective Action
III. BLOWER RUNS;
NO HEAT; FLAME
SAFEGUARD RELAY
LOCKS OUT
(Continued)
7. Regulator
a) Clogged vent orifice
b) No supply pressure
c) Improper manifold pressure
d) Defective regulator
a) Clean or replace orifice.
b) Check all gas cocks and piping.
c) Adjust regulator.
d) Replace regulator.
8. Burner
a) Defective burner
a) Replace burner.
IV. BLOWER RUNS;
BURNER FIRES;
FLAME SAFEGUARD
RELAY LOCKS OUT
1. Low Flame Current
a) Dirt build-up on insulator
b) Minimum fire set too low
c) Defective burner
a) Clean dirt deposit from insulator.
surface and install protective boot.
b) Adjust minimum fire on modulating valve.
c) Replace burner.
2. Multi-Functional PC Board
a) Low fire start set too low
a) Adjust modulating valve voltage between
9 and 13 Volts DC.
3. No Flame Current
a) Ground connection open
b) Wire termination oxidized
a1) Reference transformer to ground.
a2)
Secure FSR grounded.
a3) Tighten loose ground screws.
b) Clean terminal and reinsert.
4. Fluctuating Flame Current
a) Unit overfiring
b) Minimum fire set too low
c) Intermittent ground connection
d) Defective burner
a) Check manifold pressure.
b) Adjust minimum fire on modulating valve.
c) Tighten all ground points.
d) e) Replace burner.
5. Flame Safeguard Relay
a) Defective FSR
a) Replace FSR.
6. High Limit
a) High limit contact intermittent
a) Replace high limit.
V. BLOWER RUNS;
UNIT HEATS;
SHORT CYCLES
WITHOUT
RESETTING
1. Air Flow Switch
a) Blower running backwards
b) Belts slipping
c) Blocked intake or discharge
d) Air delivery below minimum
requirements
e) Clogged airflow tubing or pick-up ports
f) Defective switch
a) Reverse motor direction.
b) Tighten and/or replace belts.
c) Find and remove obstruction.
d) Increase fan RPM for air delivery
requirements.
e) Clean or replace airflow tubing or pick-up
ports.
f) Replace switch.
2. Flame Safeguard Relay
a) Defective FSR
a) Replace FSR.
3. Operating Thermostat
a) Differential temperature setting too tight
a) Increase differential temperature setting.
4. Damper Motor End Switch
a) End switch making intermittent contact
a) Replace end switch assembly.
