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Megger
(Appliance Testing)
The information given below is intended only as a guide and not as a training programme. Any action taken in reference to this information is done so at the complete release of any liability regarding loses; in any and all respects, damage: directly, indirectly or consequential and injury; to either yourself or any third party/s.
To the best of our knowledge the information given here is correct and complete for the purpose intended, and we will not be deemed liable for any omissions or errors found in these articles.

It is all too easy to say for electrical testing you need a meter but that really doesn't help a large portion of people needing help with their appliance. So this section is to try to demystify the concept of the test meter and educate those amongst us that are not quite as familiar with it as others.

A multi meter which is very useful for determining continuity (breaks in wires or circuits) can be bought on ebay for around 5 pounds, and although it can be used for a number of different tests including voltage and some resistance testing it is not powerful enough to be used as a resistance tester on Domestic appliances where the voltage has to be at least 500volts DC. However this is possible on the Megohms setting of a Megger TM. A multi-meter is therefore somewhat restrictive and should only be used as previously stated for continuity testing, however the buzzer function on these meters is very useful if you are unable to easily see the dial.

The Megger TM is another type of meter for testing electrical circuitry, however this meter is confined to just testing Ohms (), Kilohms (k) and Megohms (m), and is perfect for testing resistances between cables and connections on all domestic appliances. The main problem with this type of meter is its price, unlike the cheaper multi-meter; these meters are usually rather more expensive, but are well worth the added expense if you are an engineer or even a dedicated DIY enthusiast.

When any electrical testing is carried out the power should be turned OFF and where possible the mains plug should be removed from the power socket. In the case of appliances which are hard wired (Wired directly into a wall socket without a plug). The fuse should be removed from the socket as well as the socket being switched OFF.
A CONTINUITY TEST
This test is to ascertain if there is a break in the wiring or connection between two points; such as the Timer/module to the pump (for instance). A wiring diagram is always useful but if you don't have one then patience and a good eye for following wires is the next best thing.
Trace the wire from the component back to the supply, i.e. timer / module and place a probe at one end of the wire and the other at the opposite end. With your meter set to Ohms () press the button and if the wire is good you will get a reading of about 0.5 () or less, (as shown in the photo below),but don't be too concerned if the reading is slightly above this because you may not have a perfect connection. If on the other hand the needle goes right across the dial to 200 () then you have a break in the wire / connection.
AN INSULATION TEST
This tests if there are any earth leakages on the machine. Not a dead short that would blow the fuse in the plug but a minor short that would trip your fuse box (if you have one with a reset switch), or cause your appliance to become faulty. This type of short is harder to locate because the normal Ohms setting on your meter will not register any fault; that is why the much higher voltage which is generated by the Megohms setting is required.
Make sure the door is closed before you commence the test with the on/off button in the ON position. Some machines require the mains power to be on to operate the door switch, if you have one of these then select any program and switch the power on, wait until you hear the door lock energize then turn the power off from the wall socket and remove the plug (for safety) but leave the on/off button on the machine ON

Select the Megohms (M) setting on your meter then connect one of your test probes to the positive terminal of the plug, or on the live wire where it connects to the machine. With the other probe connect to the cabinet or any part of the machine that is earthed. When you press the button on the meter you should get a reading of above 2 Megohms, this would indicate there are no earth leakages on the positive side of you machine. Redo the test this time connecting to the neutral terminal of the plug, if the reading is the same you have no earth leakage on your machine. If the needle moves across the dial past the 2 Megohms you should investigate more thoroughly and refine your testing to individual components such as the heater the motor the pump and even the thermostats could cause problems. The most common cause for earth leakage is the carbon from the brushes; it sits inside the motor casing and forms a bridge from the brush gear to the earthed casing. Usually just brushing the carbon out of the casing will cure this. This test will also show up earth leakages if you have poor insulation on the wiring.
The general rule of thumb with this test is if your meter reads 2 Megohms or above (on both positive and negative terminals) then your insulation is OK.

To test components individually
Because this tests components individual neither the on/off or door switches need be operated
First remove the connecting wires from the component to be tested,if it has an earth wire then leave that connected. Place one probe on either of the terminals and the remaining probe on an earth connection such as the cabinet. With your meter set to Megohms you should get a reading of 2 (M) or above, if it goes across the dial then the component is shorting out and needs investigating. It may be that you have a water leak and it has dripped on the electrics, so investigate before condemning the component to the rubbish bin. It could save you money.

It is advisable to avoid using the Megohms test on any module, control board or even directly on any neon/LED because the high voltage could damage the component beyond repair.