Icm2 Does Not Run; Icm1 Does Not Run; Icm2 Check−Out; Icm1 Motor And Vsp1 Checkout - Lennox G21Q3-40 Unit Information

B − ICM2 Does Not Run
To check−out the ICM blower and the VSP blower control
board, begin with the ICM blower. Refer to figure 76 and fol
low the check−out procedure as outlined. If the blower fails
any of these tests, do not attempt to repair the VSM blower.
There are no field serviceable parts in this component. Re
place the motor and repeat the check−out procedure. To
verify proper operation of the VSP, check the board as out
lined in the troubleshooting flowcharts on the last page.
If a power interrupt occurs during a demand cycle and the
heat exchanger is still hot, the blower may begin cycling on
and off with the gas valve when power is restored. This con
dition may continue until the demand is satisfied. It is recom
mended that the lower setting of the modulation control
(marked FAN OFF) be reduced by 10_F to 20_F if this prob
lem should occur. This condition will not occur in zoned ap
plications.
ICM2 CHECK−OUT
A kit is available from the Lennox parts center to use in testing the
variable speed motor. The kit 70J11 includes a test plug harness to
facilitate ICM2 check−out. Follow testing procedures outlined in
the instructions provided with the kit. The testing procedures
are different than those listed below.
If not using the kit to test the motor, follow the procedure below.
NOTE−Any A.C. voltage source less than 30 volts or any D.C. voltage
source less than 20 volts may be used to check out the motor. An ordinary 9
volt battery is recommended. Unit transformer T1 secondary may be used
in lieu of a battery. A 9 volt battery will last for about one day of normal opera
tion. If transformer T1 is used, double check all wiring connections before
placing unit back in operation.
CHECK−OUT PROCEDURE USING J46 ON MOTOR
1 2 3 4 5 6 7 8
J46
ICM2 LOW SPEED CHECK−OUT
1− Disconnect power to unit.
2− Disconnect 13 pin plug J46 from P46 located on VSP2−1.
3− Connect voltage source as shown above.
4− Turn on power to unit. Blower should
operate at low speed.
1 2 3 4 5 6 7 8
J46
5− Disconnect power to unit.
6− Connect voltage source as shown above.
7− Turn on power to unit. Blower should operate at high
speed.
1 2 3 4 5 6
J46
ICM2 HEATING SPEED CHECK−OUT
8− Disconnect power to unit.
9− Connect voltage source as shown above.
10−Turn on power to unit. Blower should operate at heating
speed.
FIGURE 76
9 10 11 12 13
9 10 11 12 13
ICM2 HIGH SPEED
CHECK−OUT
7 8 9 10 11 12 13
C − ICM1 Does Not Run
If the motor does not run the problem could be with the elec
tronically controlled blower motor or the VSP1. Check all con
nectors and wire terminations for good contact. Figure 77
shows the electronically controlled blower motor and VSP1
checkout procedure. The checkout procedure may be used
to determine if either of these components must be replaced.
The procedure bypasses the VSP1. If the electronically con
trolled blower motor does not operate properly it must be re
placed. If the electronically controlled blower appears to be
operating properly, replace the VSP1. For a detailed trouble
shooting chart see G21V/GSR21V V" Blower and VSP1
Blower Control Board Troubleshooting Flow Chart.

ICM1 MOTOR AND VSP1 CHECKOUT

POWER CONNECTOR J48
1 2 3 4
WARNING−DISCONNECT P49 FROM J49 BEFORE BEGINNING THIS
CHECKOUT. FAILURE TO DISCONNECT P49 WILL DAMAGE VSP1.
NOTE−Any A.C. voltage source less than 30 volts or any D.C. voltage
source less than 20 volts may be used to check out the motor. An ordinary
9 volt battery is recommended. Unit transformer T1 secondary may be
used in lieu of a battery. A 9 volt battery will last for about one day of nor
mal operation. If transformer T1 is used, double check all wiring connec
tions before placing unit back in operation.
CHECKOUT PROCEDURE:
1− Disconnect power to unit.
2− Disconnect P49 from J49.
3− Connect voltage source as shown below.
4− Turn on power to unit. Blower should operate on low speed
heat/cool tap.
5− Disconnect power to unit.
6− Connect voltage source as shown below.
7− Turn on power to unit. Blower should operate on high speed
cool tap.
8− Disconnect power to unit.
9− Connect voltage source as shown below.
10−Turn on power to unit. Blower should operate at high speed heat
tap.
Page 55
SPEED TAPS CONTROL CONNECTOR J49
3
2
1
LOW SPEED CHECKOUT
J49
3 6
2 5
1 4
HIGH SPEED COOL CHECK
OUT
J49
3
6
2
5
4
1
HIGH SPEED HEATING CHECKOUT
J49
6
3
5
2
1
4
FIGURE 77
6
5
4