Webasto Storage Cooler Service Manual

Troubleshooting – Refrigerant Compressor

If a ground fault does not exist, leave the power off and all external components disconnected from the terminal pins.

Check for continuity and proper resistance using the procedure under Section 5.4.2.

Why use a megger or Hi-Pot?

A conventional ohmmeter will not reliably detect a ground fault under certain circumstances.

A megohmmeter (“megger”) is a special type of ohmmeter that is capable of measuring very high resistances by using high voltages.

A Hi-Potential Ground Tester (“Hi-Pot”) is a device that uses high voltages to measure the flow of current across the insulation. Unlike an ohmmeter, even one that can measure millions of ohms, a megger or a Hi-Pot can detect a breakdown in motor winding insulation before the motor fails.

WARNING! To reduce the risk of electrocution, always follow the manufacturers’ procedures and safety rules.

Figure 21. “Megger” and “Hi-Pot”

“megger”

“Hi-Pot”

5.4.2

Checking for Continuity and Proper Resistance

If no ground fault has been detected using the procedures under Section 5.4.2, determine whether there is an open or

short circuit in the motor windings or if the heater element of the thermal protector is open.

Use the procedures in Table 5 to check the single phase motor.

Step 1: Allow Thermal Protector to Reset

When servicing single compressors with internal thermal protectors, be sure to allow time for the thermal protector to reset prior to starting these electrical wiring checks.

Step 2: Check Continuity

Check the start winding by measuring continuity between terminal pins C and

S. (See “Identification of Hermetic Terminal” on page). If there is no continuity, replace the compressor. See “System Cleanup and Compressor Replacement

After Compressor Failure” under Section 6.1.

Check the run winding by measuring continuity between terminal pins C and R.

If there is no continuity, replace the compressor.

Table 5. Checking for Proper Continuity and Resistance

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