Steffes DLF40B - Manual (Page 31)

Troubleshooting Information
(cont'd)
30
B. PROBLEM: FURNACE WILL NOT DELIVER HEAT
With room thermostat call for heat, check
LED's on charge control circuit board panel
(30). "POWER ON" & "HEAT CALL" lights
must both be ON.
Jumper room thermostat
connections "R" and "W"
terminal block positions
on the charge control circuit
board (30).
Lights Off
Check for core blower
motor (38) operation.
Lights On
Repair room thermostat
or field wiring. Check for 24 VAC between
room thermostat connection
"C" terminal block position and
the two 3­amp low voltage
fuses on the charge control
circuit board (30).
Check core blower relay
operation (34). (Top relay in
furnace electrical panel.)
Check wire connections below
charge control circuit
board (30) and/or change the
charge control circuit
board (30).
Check unit wiring
and/or replace
defective control
transformer (28).
Check heat exchanger and
core blower limit switches
(27 & 53) & core blower
speed switch (69).
Check core blower
relay coil voltage
for 24 VAC.
Core Blower Runs
Core Blower
Does Not Run
Core Blower
Does Not Run
Ok
Inoperable
Replace defective
switch(es).
Check core blower
motor (38) & unit wiring.
Replace core
blower relay (34).
Replace charge
control circuit
board (30).
Ok
No Voltage Ok
Defective
Remove supply air plenum cover. Check heat exchanger
temperature should be 135ºF minimum with core blower running.
Ok
No Voltage
Core Blower
Runs
Low or no core
charge or core
blower wheel
(36) problem.
No Heat
Check for contact closure on supply air blower switch (52).
Check supply air blower limit (54), core blower motor (38), & voltage
between blue & blue/red wires on supply air blower motor (58) supply cable.
(NOTE: In heating mode the supply air blower motor (58) runs on the
normally closed relay contact. Relay is not pulled in for heating.)
Replace supply air
blower switch (52).
Will Not Close
Ok
Ok