TideLog Posts Tagged “flashing lights”

In this article I’m going to help you diagnose and identify control problems in your washing machine. Modern washing machines all contain a computerized timer and control system, this is responsible for controlling all the different circuits in the machine such as the sensor network, motor, drainage circuit and the heating circuit. The main thing to remember, whether diagnosing a modern sensor washer, or a car electrical network, is that computers run off the same basic principle. Inputs and outputs, if a computer can’t get a reading or signal from an input, the output can’t happen, either at all, or efficiently, the computer then has to fall back to what are known as “reference values” stored in a ROM. An example of this in a washing machine, is if the computer can’t determine the water temperature, it can’t heat it correctly.

An example in a car would be if it can’t detect how much fuel is being injected to the electronic injectors, the emissions are affected and it has to fall back to reference values stored in “injection maps” in the ECU as it’d be using too much fuel and it would cause combustion problems.

If you suspect that there’s a fault in one of the circuits in your washing machine it’s usually much easier to test all the components in the circuit before suspecting that the problem lies in the control board. Problems in the wiring network of a machine are much more likely the cause. For example in the drainage circuit you would check the drain pump and the wiring; the heating circuit you would check the element, the thermostat and the wiring. If you then suspect that the problem still lies in the circuit board unfortunately it’s usually quite difficult for inexperienced people to test the board and you’ll actually just need to replace it altogether or consult an electronics guy like me.

The first problem we’re going to look at is program issues. Most modern machines are designed to shut down if they detect a fault somewhere in the system and this is usually accompanied by a fault code. A fault code is displayed on the front of the machine as a combination of letters and lights or numbers. These fault codes vary from one manufacturer to another so it can actually be just as helpful to watch your machine to diagnose where the fault is, such as in the drainage circuit or the heating circuit. When you turn your machine on, the first thing it does is to lock the door via the electronic door lock solenoid and it’s then that it performs a self-check. If in the self-check it detects a fault somewhere in the system it’ll shut down and display a fault code, or if the door doesn’t lock properly it’ll also detect that as a fault and shut down.

Once the machine has passed the self-check stage, it will proceed to fill with water through the fill valves (solenoid valves) at the back. Most stages in a washing machine cycle are programmed to complete within a predetermined time so if your machine doesn’t recognise that it’s filled within a couple of minutes it will usually shut down and display a fault code to stop any flooding occurring. Assuming that’s OK and the machine has filled with water it will then move on to the next stage in the wash cycle. Once the water has filled to the correct level the machine will then start to agitate it and heat it if required by that particular cycle. Once the temperature has been reached the machine will then wash for a certain amount of time before draining the water away and again, this has to happen within a predetermined time so if it doesn’t, the machine will shut down and display a fault code.

Once the water’s drained it will then do a short spin and this is followed by the rinse cycle. The rinse cycle is very similar to the wash cycle, except in the rinse cycle the water isn’t heated; water is brought in to a predetermined level within a certain amount of time, it’s then agitated, before being drained away. Most machines have at least two rinses in the rinse cycle and on the final rinse both solenoid valves at the back of the machine open up and flush any conditioner from the detergent drawer down into the drum. Once the machine has completed the rinse cycle it will prepare for the final spin by balancing the load. It does this by attempting to evenly distribute the weight of the load around the drum by using sensors to detect drum wobble on either side of the drum. However, if the load contains a particularly heavy item – such as a pair of jeans or a towel – amongst an otherwise lighter load, it will attempt to balance that heavier item amongst the load. If it can’t balance the load it will simply refuse to spin or it may just shut down and display a fault code.

However, once the load has been balanced the machine will spin and complete the wash cycle. If your machine is dead and it’s not displaying any lights or anything on the front then you’ll need to check it for continuity. Firstly, just unplug it from the wall and have a look at the fuse inside the plug to make sure it hasn’t blown; once you’ve established that it hasn’t, you’ll need to check for continuity between the plug and the control board. Don’t just replace the fuse and plug back in, the fuse has blown for a reason, and until the reason is found and fixed it will likely blow more fuses.

If you follow the path of the plug in through the machine, some will come through to a filter board, it then passes along to the plug on the control board. Grab a multimeter on a resistance or continuity setting and just check for continuity between the two. If you can see that there’s continuity on both connections, that shows power is getting to the circuit board, but there’s probably a fault inside – the way we need to check is by replacing the board with a new one.

Next, let’s have a look at if your machine is blowing a fuse when you plug it in; usually this is caused by a short circuit somewhere in the machine and the short can either exist in the control board or within components around the machine. You can check very easily for a short if you unplug the machine and, using a multimeter on a resistance reading, check for the short across the plug through live and earth, and live and neutral. If there is a short there it’s going to show up as a resistance reading of less than a couple of ohms. Often the first thing to short is the heating element, so try disconnecting that and testing again for a short circuit; if the short has gone then that would indicate that the short does lie in the element. Obviously you can double check by testing the element itself and for a working element the reading you’re looking for is somewhere between twenty and fifty ohms so anything outside of that reading means you’ll need to replace the element.

On the other hand, if removing the element doesn’t get rid of the short the next thing to disconnect is the circuit board and again, once you’ve done that, check for a short there. If the short still hasn’t gone, move further along the line and try checking on the filter board. If the short still hasn’t gone then then it’s likely to be in the plug and the cable and you’ll need to replace those. To test the element, first disconnect the connector lugs and then turn your meter onto a high resistance setting and measure from earth to one of the terminals – from this you shouldn’t get a reading. Then put your meter onto a low resistance setting and measure across the element – on this one I’m getting a reading of about twenty-seven to twenty-eight ohms, so that indicates that this one is OK.

If your machine is tripping the electricity, the process for diagnosing is largely the same, however it may be that a normal meter won’t show any fault being present. In such a scenario an engineer would use an insulation tester such as a Megger and this produces five-hundred volts for determining where the breakdown has occurred. Again, it’s likely to be due to the heater, or heaters if it’s a washer-dryer appliance, but if the tripping is occurring during the final spin the motor is likely to be at fault, where it’s being worked at its hardest during that part of the cycle. One final thing about control boards and tripping faults is that a lot of the time it can be difficult to conclusively diagnose the fault; sometimes a fault that’s being caused by another component actually appears to be caused by the control board. Similarly, if you’re replacing the control board, many of them now require professional programming on installation.

I’m here to help, don’t be afraid to ask!

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