Specifications
Table 25 — Economizer Control Board Checkout,
Test 3
MOTOR
TEST
PROCEDURE
EXPECTED RESULT
AND RESPONSE
A
Turn mixed-air potenti-
ometer to the midpoint
position.
Motor should drive to mid-
stroke with the set point set
between 60 and 70 F. If not,
the control board is faulty.
B
Turn mixed-air potenti-
ometer fully counter-
clockwise.
Motor drives open, If not, the
control board is faulty.
C
Turn mixed-air potenti-
ometer fully clockwise.
Motor drives closed. If not,
the control board is faulty.
Test 4
Refer to Table 26 for the correct procedure for test 4.
Table 26 — Economizer Control Board Checkout,
Test 4
MOTOR
TEST
PROCEDURE
EXPECTED RESULT
AND RESPONSE
A (Outdoor-
Air Sensor)
1. Connect the enthalpy
sensor terminal 1 to
terminal 1 on the
motor.
2. Connect the positive
terminal of a DC mil-
liammeter to terminal
S of the sensor.
3. Connect the negative
terminal of a DC mil-
liammeter to terminal
S
O
of the enthalpy
board.
Milliammeter reading
should be between
3 and 24 mA if the sen-
sor is operating cor-
rectly. If the reading is
0 mA, the sensor is ei-
ther wired backward or
is defective.
B (Indoor-
Air Sensor)
1. Connect the enthalpy
sensor terminal 1 to
terminal 1 on the
motor.
2. Connect the positive
terminal of a DC mil-
liammeter to terminal
S of the sensor.
3. Connect the negative
terminal of a DC mil-
liammeter to terminal
S
R
of the enthalpy
board.
Milliammeter reading
should be between
3 and 24 mA if the sen-
sor is operating cor-
rectly. If the reading is
0 mA, the sensor is ei-
ther wired backward or
is defective.
Control Board Checkout — The following tools are
required to perform the troubleshooting tasks detailed in this
section:
1.5-v battery
2 sets of jumper wires with alligator clips
Multimeter
Toggle switch with 14-in. wires terminated with
1
⁄
4
-in. spade
connectors
Read these instructions completely before attempting to
troubleshoot the control board. Failure to follow the steps
precisely could result in damage to unit, personal in-
jury, or death.
The control board checkout procedure consists of 3 parts: A
basic check to verify availability of 24 and 115 v to the con-
trol board; a detailed check of each circuit within the board;
and a continuity check for the economizer board.
BASIC CHECK — Refer to Fig. 50 for control board com-
ponent identification.
IMPORTANT: If unit is equipped with an economizer
option, disconnect and remove the economizer control
board.
NOTE: All plugs (except P1) are labeled for easy identifi-
cation. Plug P1 can be identified by its orange color.
1. Turn unit power off. Disconnect plug P1 from control board.
2. Turn unit power on and check voltage across Pin R and
Pin C at plug P1. If voltage reads 18 to 30 v, skip to
Step 5.
3. Turn unit power off. Disconnect plug P3.
4. Turn unit power on and measure voltage across wires on
plug P3, Pins 1 and 2 (wires coming from the unit). If
voltage reads 18 to 30 v, there is either a bad connection
between plug P3 and control board, or the control board
is defective. Verify the connection at this point and pro-
ceed to Step 5. If there is no voltage, check the circuit
breaker and transformer in the 24-v control circuit of the
unit.
5. Turn unit power off and disconnect plug P4 from the
control board.
6. Switch scale on meter to read 115 v.
7. Turn unit power on and check voltage across Pin 6 on
plug P4 and unit ground (wires coming from the unit). If
voltage reads 104 to 122 v, there is adequate power avail-
able to the board. Verify connection at this point and pro-
ceed to Step 8 below. If there is no voltage, check the
circuit breaker and transformer in the 115-v control cir-
cuit of the unit.
8. After verifying that 24-v and 115-v supply power is avail-
able to the control board, turn unit power off and re-
connect plugs P1, P3, and P4. Proceed to Detailed Check
section below.
DETAILED CHECK
NOTE: Plug P1 must be disconnected in order to perform
any of the troubleshooting steps detailed in this section. To
save time, reconnect plug P1 only after you have completed
all of the required troubleshooting.
Symptom: Evaporator fan will not operate.
1. Turn unit power off and disconnect plug P1 from the
control board.
2. Install a jumper across Pin R and Pin G at plug P1 on the
control board.
3. Turn unit power on and check if the indoor (evaporator)
fan contactor (IFC) coil has been pulled in. If the IFC
coil has not been pulled in, check the voltage across the
IFC coil. If there is voltage at this point, the IFC con-
tactor is defective. If there is no voltage, proceed to
Step 4.
53