Friedrich VRP12K, Service And Parts Manual

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167 PB
TROUBLESHOOTING
Diagnostic Code (Temperature Based)
Temperature Based:
Thermistors (sensors) modify VDC and is interpreted through the FMC.
Errors indicate a possible issue with the sensor, FMC, or the sensor has detected an abnormal condition (or an out of parameter
value).
Solution: Sensor error, FMC error, or abnormal condition.
VRP Sensor Bank contains 10 sensors for air and coil temperature. Each is 10k Ohm and must be unplugged from the FMC to test
against a resistance chart. The sensors have a two‑port molex connected to the FMC. They all share a common power supply which
can be checked against the other connectors for continuity and rule out the FMC.
Rule Out Thermistors :
A thermistor will only give an error code if the thermistor is shorted, 0 ohms, or opened, O/L. If the thermistor is out of range, it
may not give an error code and the system may not operate correctly.
Rule out FMC - Continuity Check
The first pin in each set can be
checked against the others to make
sure voltage has the ability to flow
through that thermistor port.
Rule out FMC - Voltage Check
The Thermistor port can be checked
without the sensor attached to
verify proper voltage is being
passed through the molex.
Voltage should be ~3.3VDC