10
TechAssist
™
Diagnostics--at--a--Glance
Single phase air conditioning units are equipped with a system diagnostics tool called the TechAssist
t
. Follow Table 4 to identify and
correct problems in system operation.
Table 4—
TechAssist
t
Diagnostics--at--a--Glance
LED
Description
ON
OFF
Y
Thermostat cooling call
Yes
No
. . . . . . . . . . .
. . . . . . . . .
. . . . . . . .
HPS
High Pressure Switch
Closed
Open
. . . . . . . .
. . . . . . . . . . .
. . . . .
LPS
Low Pressure Switch
Closed
Open
. . . . . . . . .
. . . . . . . . . . . .
. . . . .
230V
AC Line Power Available
Yes
No
. . . . . . . .
. . . . . . . . .
. . . . . . . .
Contactor
Contactor Energized
Yes
No
. . .
. . . . . . . . . . .
. . . . . . . .
Compressor Compressor Running
Yes
No
.
. . . . . . . . . . .
. . . . . . . .
Y
HPS
LPS
230V Contactor Compressor
CONTROL
POWER
→
→
→
→
→
Note: --- Follow arrows to first unlit LED in control (green) ladder or power (amber) ladder to determine problem area.
*** --- For contactor LED to be On, all control LEDs (green) as well as 230V LED (amber) must already be on, and contactor must operate . . . . .
properly
Control Ladder
Power ladder
Indication
Possible Cause & Quick
Trouble---Shooting
Green LEDs
Amber LEDs
Y
HPS LPS 230V Contac-
tor
Compressor
Off
Off
Off
Off
Off
Off
--- No 230V power to unit
--- No thermostat call
--- Check 230V disconnect/ circuit breaker
--- Check 230V L1 & L2 wire connections
On
Off
Off
--- ---
Off
Off
--- HPS Switch Open
--- Check pressures
--- Check HPS wire connections
On
On
Off
--- ---
Off
Off
--- LPS Switch Open
--- Check pressures
--- Check LPS wire connections
On
On
On
Off
Off
Off
--- No 230V power to unit
--- Check 230V disconnect / circuit breaker
--- Check 230V L1 & L2 wire connections
On
On
On
On
Off
Off
--- Contactor open ***
--- Check Contactor and replace if necessary
--- Check contactor wire connections
On
On
On
On
On
Off
--- Compressor not running*
--- Check for compressor protector trip, capacitor
fault, faulty connections or compressor fault.
SEE BELOW.
On
On
On
On
On
On
--- Compressor running
--- OK
Off
Off
Off
On
Off
Off
--- No thermostat call, standby --- OK
Off
Off
Off
On
On
Off
--- Contactor stuck closed,
compressor tripped
--- Check Contactor and replace if necessary
--- Check wire connections for shorts
Off
Off
Off
On
On
On
--- Contactor stuck closed,
compressor running
--- Check Contactor and replace if necessary
--- Check wire connections for shorts
*Compressor not running: If all LEDs are on except the Compressor, this indicates that power is applied to the compressor but it is not running. Check the
following sequence:
1) Check all compressor wire connections
2) Check run capacitor and replace if necessary
3) Try starting compressor
4) If compressor LED does not come on, then leave unit in standby for up to four hours to allow thermal protector to reset, and all pressures to equalize
5) Try starting the compressor again
6) If compressor LED comes on, then turns off quickly, investigate starting issues such as low line voltage
7) If compressor LED never comes on, compressor may be faulty.
123A
/124A
