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How to use a Multimeter:

To use the resistance readings, set the meter to the correct range and calibrate if necessary. If possible, disconnect the wires to the component and measure the dc resistance across it. If the reading is not within 10% either way of the expected value then the component is likely to have failed (make sure motors are not seized and turn freely).

It is sensible to avoid live mains electricity and we would not recommend live electrical fault tracing; the multimeter should be able to identify most problems with just the resistance reading across the suspect component.

What resistance readings should I expect?

Here below are some common resistance readings in domestic appliances designed for running on 230 volts

Heater elements in dryers, cookers, washing machines etc.

Typical 2kw 26.5 ohms

1kw element 53 ohms

500 watt element 106 ohms

Pump motor 165 ohms

Main motor ( Brush type )

Armature Between 1.5 ohms and 5 ohms on a washing machine (depends on power & spin speed)

Field windings Between 1 and 5 ohms on a washing machine (depends on power & spin speed).

Tacho coil typically 120 ohms approx.

Thermal cut out less than .1 ohms when closed (not cut out).

Sensor on wash heater

20,000 ohms at 20 degrease C

5000 ohms at 60 degrease C

1300 ohms at 95 degrease C

Bear in mind the resistance readings are directly related to the power used by the device.

For example a 15 watt mains bulb in a fridge would read approximately 3450 ohms

But a 150 watt mains bulb would read 10 times lower at approximately 345 ohms

The resistance of 15 watt bulb designed for a 12 volt system would be 9.6 ohms

And for a 150 watt bulb designed for a 12 volt system the resistance would be 10 times lower at .96 of an ohm

The above readings are given as a guide and may change depending on manufacturer.