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Table 35 — Durablade Economizer Troubleshooting
PROBLEM CAUSE REMEDY
Damper does not
open.
Indoor (evaporator) fan is off. 1. Check to ensure that 24 vac is present at terminal C1 on the IFC or
that 24 vac is present at the IFO terminal. Check whether 24 vac is
present at PL6-1 (red wire) and/or PL6-3 (black wire). If 24 vac is
not present, check wiring (see unit label diagram).
2. Check proper thermostat connection to G on the connection board.
No power to economizer motor. 1. Check that SW3 is properly making contact with the damper
blade. Check that SW1 is in the NC (normally closed) position.
2. Check diode D18. If diode is not functioning properly, replace control
board.
3. Confirm that the economizer control board is grounded properly at
PL6-4 (brown wire) and at brown terminal of the economizer control
board (brown wire). The economizer motor must also be grounded
properly at the negative motor terminal (brown wire).
4. Verify SW1 and SW3 are working and wired properly (see unit label
diagram).
5. Check for 24 vac input at both PL6-1 (red wire) and PL6-3 (black
wire). If 24 vac not present, check unit wiring (see unit label
diagram). If 24 vac is found in both places, check for 24 vac at the
yellow terminal of the economizer control board (yellow wire). If
24 vac power is not present, replace the economizer control board.
Economizer motor failure. If the indoor (evaporator) fan and economizer motor are energized,
verify that there is a minimum of 18 vdc at the positive motor
terminal. If the motor is not operating, replace the motor.
Economizer
operation
limited to minimum
position.
OAT or EC set too high. 1. Set at correct temperature (3 F below indoor space temperature).
2. Check OAT or EC by setting above outdoor temperature or humidity
level. If the OAT or EC switches do not close, replace OAT or EC.
Verify economizer control board is correctly
wired and works properly.
1. Perform the following tests when OAT or EC is closed, Y1 is called
for and damper is at minimum position. Confirm 24 vac on gray
terminal of the economizer control board (gray wire). If 24 vac is
not present, check wiring (see unit label diagram).
2. Verify that SW1 and SW3 are wired correctly and working properly
(see unit label diagram).
3. Check to ensure that 24 vac exists at PL6-2 (blue wire). If 24 vac is
not present, check wiring (see unit wiring label diagram).
4. Check 24 vac output at PL6-10 (white wire). If 24 vac is not
present, replace economizer control board.
Check SAT. 1. After verifying that the OAT and EC settings and the economizer
control board wiring are correct, check to ensure that the 24 vac
terminal of the SAT has 24 vac (white wire). If OAT, EC, and control
board are functioning and wired properly and no 24 vac exists,
check wiring (see unit label diagram).
2. If supply-air temperature is greater than 57 F, 24 vac should be
found at terminal T2 on the SAT (pink wire). If 24 vac is not present,
replace SAT.
Damper does not
close.
Incorrect wiring of economizer. 1. Verify that SW2 and SW4 are wired and working properly (see unit
label diagram).
2. Check diode D19. If diode is not functioning properly, replace control
board.
Verify economizer control board is functioning
properly.
1. After verifying that the wiring is correct, modulate the damper to the
minimum position. Remove the calls for G.
2. If the damper does not move, check for 24 vac at PL6-1 (red wire).
If 24 vac is not present, check wiring (see unit label diagram).
3. If damper still does not move, check for 24 vac at blue terminal of
economizer control board (blue wire). If 24 vac is not present, re-
place the economizer circuit board.
Check SAT. 1. After verifying that the wiring is correct and the economizer control
board is functioning properly, place the OAT or EC switch in the
closed position. Place a call for Y1 and open the damper to the fully
open position. Confirm that the 24 vac terminal of the SAT has
24 vac (white wire). If 24 vac is not present, check wiring (see unit
label diagram).
2. If supply-air temperature is less than 52 F, 24 vac should be found
at terminal T1 on the SAT (violet wire). If 24 vac not found, replace
SAT.
Economizer motor failure. If economizer control board and SAT are functioning properly, verify
that there is a minimum of 18 vdc at the positive motor terminal. If a
minimum if 18 vdc is present and the motor is still not operating, re-
place the motor.
Economizer damper
does not close on
power loss.
Verify that close-on-power-loss and economizer
control board are functioning properly.
1. Check voltage potential across batteries. If lower than 14 vdc,
replace close-on-power-loss power supply (9-v alkaline batteries). It
is recommended that you check this emergency power supply on a
regular basis or whenever the filters are changed.
2. If the close-on-power-loss and economizer control board are
functioning properly, check for 14 vdc or higher at the blue terminal
of the economizer control board (blue wire) when power is discon-
nected from unit. If 14 vdc is not present, replace the control board.
C1 —
Common Power
OAT —
Outdoor-Air Thermostat
EC —
Enthalpy Control
PL —
Plug
IFC —
Indoor (Evaporator) Fan Contactor
SAT —
Supply-Air Thermostat
IFO —
Indoor (Evaporator) Fan On
SW —
Economizer Position Switch