Amana GUIA Series Service Instructions Manual page 139

SERVICING
ally reduces the "ON" time of the ignitor. The effect is that
the ignitor operates at a cooler temperature. The learning
routine will eventually reduce the ignitor "ON" time to a point
at which the ignitor is too cold to ignite the gas. The control
will then increase the "ON" time and initiate an ignition re-
try. The furnace will light. The control will remain at this
point for 256 thermostat cycles, after which it will re-enter
the learning routine. IMPORTANT: The "ONLY" way to de-
termine if the ignitor "ON" time is changing is to view the
ignitor voltage wave form with an oscilliscope.
6. If proof of flame was established voltage will be pro-
vided to the air circulation blower following the heat on
delay period.
a. Check for 120 volts from the CIR terminal ( WH wire
on GUIA, GCIA, GUIC, GCIC, GUID, GUCA, GCCA
and GUSA models, or WH-33 wire on GUIS and GCIS
models) to the heat terminal ( Heat terminal on GUIA,
GCIA, GUIC, GCIC, GUID, GUCA, GCCA and GUSA
models, or Heat-High and Heat-Low terminals on
GUIS, GCIS and GUSA models) on the ignition con-
trol. No voltage - replace ignition control.
b. On the 80% GUIV and 90% GUVA two-stage vari-
able speed furnaces, 120 Volts will be present at the
motor at all times ( WH-33 and BK-6 wires on GUIV
and WH-45 and BK-37 wires on GUVA), even with-
out a call for cooling or heating. These motors re-
ceive their operational signals (24 Volts) through the
16-pin wiring harness (connected between the mo-
tor and interface board on GUIV-CA/DX models and
GUVA-AX models or connected between the motor
and ignition control on GUVA-BX models). NOTE:
For complete troubleshooting information on units
using the ECM/ICM blower motors, refer to the ser-
vicing section - Checking Air Circulator Blowers (S-
9A ECM/ICM) in this service manual.
NOTE: Accessory Electronic Air Cleaners and Humidifiers
powered through the ignition control accessory terminals,
under some circumstances can create interference with the
ignition control causing intermittent lockouts. If the source
of the lockouts cannot be otherwise determined, it is rec-
ommended that these accessories be disconnected from
the ignition control and powered through alternate means.
S-13A CHECKING WR50A52 INTEGRATED IGNI-
TION CONTROL (RADIANT SENSE)
NOTE: Failure to earth ground the furnace, reversing the
neutral and hot wire connection to the line (polarity), or a
high resistance connection in the neutral line may cause
the control to lockout due to failure to sense flame.
CAUTION
To avoid the risk of electrical shock, wiring to the unit
must be properly polarized and grounded. Disconnect
power before performing the following service.
The ground wire must run from the furnace all the way back
to the electrical panel. Proper grounding can be confirmed
by disconnecting the electrical power and measuring resis-
tance between the neutral (white) connection and the burner
closest to the flame sensor. Resistance should be less than
10 ohms.
The ignition control module is a combination electronic and
electromechanical device and is not field repairable. Com-
plete unit must be replaced.
The WR50A52 ignition control, controls all furnace opera-
tions including blower operation in air conditioning. Blower
time delays are controlled by the ignition control and are
nonadjustable, see the specification section for blower de-
lay information.
WARNING
LINE VOLTAGE NOW PRESENT.
These tests must be completed within a given time frame
due to the operation of the ignition control. See "Sequence
of Operation" section for timing chart.
1. Check for 120 volts from Line 1 (BK6 wire) to line 2
neutral (WH-33 wire) at the ignition control. No voltage
- check the door switch connections and wire harness
for continuity.
2. Check for 24 volts from W to C at the thermostat con-
nections on the ignition control. No voltage - check trans-
former, room thermostat, and wiring.
3. Check for 120 volts to the induced draft blower by mea-
suring voltage between IND (VT-55) and neutral. No
voltage - check for pressure switch stuck closed. If pres-
sure switch in N.O. position replace ignition control.
4. If voltage is present in Steps 1 through 3 and the in-
duced draft blower is operating, check for 120 volts to
the ignitor during the 17 second preheat cycle. If the
flame switch has not transferred, the control will con-
tinue to power the ignitor until the flame switch trans-
fers, or for 90 seconds. Voltage will be present for one
second after the gas valve has opened. Measure volt-
age between terminals IGN (RD-22) and neutral. No
voltage - check pressure switch.
5. Seventeen seconds after a call for heat begin checking
for 24 volts to the gas valve. Measure voltage from ter-
minal 5 (YL-8 wire) to terminal 3 (RD-5) on the gas valve.
No voltage - check flame switch and ignitor position.
6. If proof of flame was established 120 volts will be pro-
vided to the air circulation blower 45 seconds after the
gas valve opens. Check for 120 volts from the CIR ter-
minal (WH) wire to the heat terminal on the ignition con-
trol. No voltage - replace ignition control.
NOTE: If cycling the ignition control during testing, the flame
switch must be allow to cool and switch back to the N.C.
position before the next ignition attempt.
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