Friedrich VRP12K, Service And Parts Manual

Page: 172 / 221

172 PB
TROUBLESHOOTING
Diagnostic Codes
Diag
#
Description Diagnostic Check point Solution
1 Front panel switch is stuck If a button is stuck (on > 20 sec)
2 Input Voltage out of Specification
1. The AC line voltage is out of specification
2. The AC line voltage is monitored by
the PFC processor on the MCS board
3
Ambient Indoor Air sensor
(T8) is open or shorted
1. An open or shorted sensor is detected
by the A/D conversion value residing at the
upper or lower end of the conversion range.
2. The Ambient Indoor Temperature
Sensor(T8) is open or shorted
3. Defective contact between
male and female electrical
molex connectors.
4. The sensor is not properly
connected to the FMC.
1. Disconnect the sensor at the FMC then
reconnect.
2. Ohm out the sensor to determine the
failure point and correct as needed.
Refer to Component Testing (Thermistor
Values)
3. Replace the FMC board.
4
Indoor Coil Cool Inlet sensor
(T1) is open or shorted
5
Outdoor Coil Heat Inlet sensor
(T7) is open or shorted
6 Discharge Air sensor (T9) is open or shorted
7
Outdoor Ambient Air sensor
(T10) is open or shorted.
8
Indoor Coil Heat Cond. sensor
(T5) is open or shorted.
9
Compressor Discharge sensor
(T4) is open or shorted.
10
Compressor Suction sensor
(T3) is open or shorted.
11 Liquid Cool sensor (T6) is open or shorted
12 Liquid Heat sensor (T2) is open or shorted
13 Humidity sensor (T12) is open or shorted.
1. The wall controller is not properly
connected to the
FMC.
2. There is an issue with the sensor itself.
3. The Humidity sensor (T12) is open or
shorted
1. Ohm out the sensor to determine the
failure point and correct as needed.
Refer to Component Testing (Thermistor
Values).
2. Verify that the wall controller is correctly
connected to the unit, if it is and the problem
persists, replace the wall controller.
14 Pressure Limit Switch Open
1. The Pressure Limit Switch is open
2. The Pressure Limit Switch will
open if the pressure in and around the
com‑ pressor becomes too small
19 Outdoor Coil > 175°F
1. The Outdoor Coil reaches a temperature
greater than 175°F
2. ODF is not running when the compressor
is on in cool.
3. Improperly pinched EEV position <100
steps.
4. Seal system blockage.
1. Ensure that the ODF is properly connected
and operational
2. Open the EEV >300 and see if the rectifies
the issue.
3. Remove Blockage
4. ODF replacement
20
The Indoor Coil at sensor T1’s location
reaches a temperature < 30°F and
remains there for 5 consecutive minutes
1. Lower than usual IDB speeds.
2. Low refrigerant charge.
3. Low Ambient.
1. Ensure that the IDB is connected properly
and is operational.
2. Check that there is no blockage in the duct
work.
3. Check the filter.
4. Check for refrigerant leaks and reprocess.
21
Unit cycles (heat or cool demand)
> 9 times per hour
1. Unit is oversized for the space
2. Wall controller is placed in a position
where the temperature is grossly off of the
actual room condition.
1. Ensure that the wall controller’s
placement is “correct” based on room air
flow