Service manual

SERVICING
43
1. You must have the correct replacement module. The
controls are factory programmed for specific operating
modes. Even though they look alike, different modules
may have completely different functionality. Using the
wrong control module voids all product warranties and
may produce unexpected results.
2. Remove all power from the unit being serviced. Do not
work on the motor with power applied. Wait at least 5
minutes after disconnecting power from the equipment
before opening the motor.
3. It is usually not necessary to remove the motor from the
blower assembly. However it is recommended that the
whole blower assembly, with the motor, be removed.
Unplug the two cable connectors to the motor. There
are latches on each connector. Do not pull on the wires.
The plugs remove easily when properly released.
4. Observe the flat end of the motor control module casting
and located the two standard ¼" hex head bolts. Re-
move these bolts from the motor while holding the con-
trol module. Do not remove the two torx head screws.
5. The control module is now free of the motor but still at-
tacked by a plug and cable. Carefully rotate the control
so as to gain access to the plug on the end of the cable.
Squeeze the release latch and gently pull the plug out
of the control module. Do not pull on the wires. Grip the
plug only.
6. The control module is now completely detached from the
motor. Verify with a standard ohmmeter that the resis-
tance from each motor lead (in the motor plug just re-
moved) to the motor shell is greater than 100k ohms.
(Measure resistance to unpainted motor end plate). If
any motor lead fails this test do not proceed to install
the control module. The motor is defective and must be
replaced. Installing the new control module will cause it
to fail also.
7. Verify that the replacement control module is correct for
your application. If so, orient the new module next to
the motor and carefully insert the plug removed in step
5. Be sure the plug latches. It will click when properly
inserted.
8. Install the new control module back on the motor being
careful to engage the locating pin into the appropriate
mating motor hole. Replace the two 1/4" hex head bolts.
Tighten the bolts snugly. It is not necessary to over-
tighten.
Note: Before replacing the blower/motor assembly, it is im-
portant to look at the installation to see if some application
fault has caused the motor to fail.
Is there any evidence of water damage to the failed con-
trol? (Corrosion on the inside or outside of the casting.) If
yes, do moisture check.
9. Re-install the blower/motor assembly into the package
unit.
10. Plug the 16-pin control plug into the motor. The plug is
keyed. Make sure the connector is properly seated and
latched.
11. Plug the 5 pin power connector into the motor even
though the plug is keyed, observe the proper orienta-
tion. Do not force the connector. It plugs in very easily
when properly oriented. Reversing this plug will cause
immediate failure of the control module.
12. Final installation check. Make sure the motor is installed
as follows:
A. As far into the blower housing as possible
B. Belly bands not covering vent holes or on the
control module
C. Motor connectors should oriented as to prevent
the accumulation of moisture in the control.
D. Use wire ties to create a drip loop in the motor
cables.
13. The installation is now complete. Reapply power to the
package unit and verify that the new motor control mod-
ule is working properly.
S-300 TESTING PRIMARY LIMIT CONTROL
Amana Package Gas Units use a snap-disk type primary
limit device. Sometimes referred to as "stat on a stick". The
limit setting is fixed and must not be readjusted in the field.
THERMODISC (TOD) LIMIT CONTROL
Refer to the specification section to determine the proper
limit cutout temperature for the model being serviced.
In all instances the limit control is wired in series with the
ignition control.
If the temperature within the furnace should exceed this
setting, the control will open, de-energizing the ignition con-
trol which in turn will open the electrical circuit to the gas
valve.
The control will automatically reset when the temperature
within the combustion chamber is sufficiently lowered.
WARNING
Disconnect Electrical Power Supply:
1. Remove electrical power to unit. Some units may have
more than one source of power.
2. Remove the wires from the limit control terminals.
3. Using an ohmmeter, test for continuity across the two
terminals.