Friedrich MW09C1H Service Manual page 51

Troubleshooting
Analysis or processing of some of the malfunction display:
1. Compressor discharge protection
Possible reasons: shortage of refrigerant; blockage of air filter; poor ventilation or air flow short pass for condenser;
the system has noncondensing gas (such as air, water etc.); blockage of capillary assy (including filter); leakage
inside four-way valve causes incorrect operation; malfunction of compressor; malfunction of protection relay;
malfunction of discharge sensor; outdoor temperature too high.
Processing method: refer to the malfunction analysis in the above section.
2. Low voltage over current protection
Possible reas on: Sudden drop of supply voltage.
3. Communication malfunction
Processing method:Ch eck if communica tion signal cable is connected reliably.
4. Sensor openo rs hort circuit
Processing method: Check whether sensor is normal, connected with the corresponding position on the
controller and if damage lf lead wire is found.
5. Compressor overload protection
Possible reasons: insufficient or too much refrigrant; blockage of capillary and increase of suction temp.;
improper running of compressor, burning in or stuck of bearing, damage of discharge valve;
malfunctioning of protector.
Processing method: adjust refrigerant amount; replace the capillary; replace the compressor; use
universal meter to check if the contactor of compressor is fine when it is not overheated, if not replace
the protector.
6. System malfunction
i.e.overload protection.When tube temperature (Check the temperature of outdoor heat exchanger
when cooling and check the temperature of indoor heat exchanger when heating) is too high,
protection will be activated.
Possible reasons: Outdoor temperature is too high when cooling; insufficient outdoor air circulation;
refrigerant flow malfunction.
please refer to the malfunction analysis in the previous section for handling method .
7. IPM module protection
Processing method:Once the module malfunction happens,if it persists for a long time and can not be self- canceled,
cut off the power and turn off the unit,and then re-energize the unit again after about 10 min. After repeating the
procedure for sever times, if the malfunction still exists, replace the module.
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