About 2 years ago, when after nearly 10 years of uninterrupted service our trusty Fisher and Paykel GW609 washing machine failed to start I wasn’t sure what to do. Should I buy a new one? Or should I try to repair it and in the process, save the environment of more plastic, lead, and who knows what else?
I felt that at least I should give the repair a go. But I didn’t have much time, I was under pressure by ‘management’ to get it going or get a new one…but soon!
And so I began searching the Net for schematics, technical info and anything helpful I could find. But very little was forthcoming. Only a few posts here and there but nothing substantial, the general consensus were that most of the faults are to do with the Control Module. The most useful information found was a copy of the service manual (attached) with a listing of the fault codes, but no reference to the Control Module or its schematic. It seems no one had been able to repair the Module and that this part is considered a throwaway by the manufacturer when faulty, to be replaced with a new one when it fails. This seemed like a waste of natural resources and money and so I decided to take a good look at it and check it, to see if it was really faulty and if so, could be repaired.
Step 1: Take Care!
UNPLUG THE MACHINE BEFORE OPENING THE CONTROL PANEL !
During the repair, always double check and take a look at that plug to make sure it is off the wall before doing anything inside the machine.
Yes, here we are going to deal with possible electrocution if you are careless because the control board and peripherals are all connected to mains. So remove that plug before touching anything…and don’t forget there is water everywhere too!
Step 2: Opening the Control Panel
Make sure the plug is off the wall. It is convenient if the washing machine is empty of water and washing because the water level sensor will not be affected when it is disconnected, and latter on re-attached, during the repair.
Remove the 2 screws at the back of the Control Panel (see pic), and lift the Panel off the machine from the back rotating towards the front (see pic). You will see the Control Module (a long bluish plastic box with many cables and plugs) still attached to the machine. The Control Panel is connected to the Control Module by a cable with a plug. Disconnect this plug from the module and put the Control Panel aside in a safe place.
NOTE: all of the sockets in the Control Module have small plastic latches that secure the plugs to the sockets; you have to carefully unlatch the plugs to unplug them (see pic).
Step 3: Removing the Control Module.
At this point, if you have a Digital Camera handy, take one or two photos of the whole thing and keep it for reference later on, when re-attaching everything back.
First, with great care remove the pressure sensor hose from the Pressure Sensor by first removing the spring clip towards the hose and pushing the edge of the hose away from the sensor (see pic). Do not pull from the hose as this will grab the sensor’s plastic pipe and possibly break it! Take care, as the hose will most probably be stuck to the sensor by years of close contact.
Next, unplug the spade connectors on the top-left corner noting their positions. This is very important because they are the mains and the ground connections and these must go back to the exact same locations.
Now remove all the plugs from the Module (they are all of different sizes so there is no need to put marks on them for when reassembling).
After removing all the plugs from the Control Module, there are still two cables left going to the hot and cold water valves, and both have connectors pointing downwards (see pic). With care disconnect these 2 connectors but put marks on them (like RED and BLU) to re-attach correctly because these two are of similar size.
With everything disconnected from the Module, remove the screw that secures the Module to the machine and lift it clear off the machine.
Step 4: Opening the Control Module
The Control Module consists of a long PCBoard, enclosed in a 2-part plastic box. This box can be easily pried open by un-clipping 3 plastic tabs along one of the sides of the box. Once the box is open, the control board can be taken out of the box by also un-clipping the retaining plastic tabs (see pics).
Step 5: Repairing the Control Board: Checking the Fuses.
For this step we need a Digital Multimeter (DMM).
There are 2 fuses on the board (see pic), one of 1.6A and the other of 4A, both type ‘T’ (slow-blow). Set the DMM to the Diode-Check range and test the fuses for continuity. Replace the faulty ones.
In the lapse of 1 year, I had to repair my board 4 times, mainly due to the fact that initially I could not find the original transistors or their exact equivalents and the replacements I fitted weren’t quite up to the job. In all cases the 1.6A fuse had blown, only in the last repair the 4A fuse had blown as well.
I replaced the original fuses with the more common 20mm type, by soldering leads to them and placing them near their original position (see pic). During the last repair I decided to mount a fuse holder as well, only for the 1.6A fuse, as there isn’t enough room in the box for the other one.
Step 6: Repairing the Control Board: Checking the Power Mosfets.
With the DMM still set to the Diode-check range, check each one of the Power Mosfets (about 12 of them) the following way: connect the probes to the small two outer pins (the center one is connected to the tab that is soldered to the board) and look for a short circuit indication (see pic). With care desolder and replace the shorted (faulty) mosfets. During my first repair I replaced four Power Mosfets, then two in the 2nd, then another two in the 3rd, and then another two in the 4th. Only two were the same transistors. Every time one of the Power Mosfets blows, also the medium power mosfet (the driver) blows and needs to be changed (see pic). But before replacing it, once removed double check with the DMM that it is shorted, just in case the short is on the diodes or somewhere else. When desoldering the Mosfets, heat up the tab first and then the pins, all in quick succession while carefully pulling with long nose pliers until freed from the board. This operation is difficult because the Mosfets are glued to the board during manufacturing and you have to crack the tiny bond before the Mosfet can be removed. Be very gentle not to damage the board as it can be easily damaged.
Step 7: Repairing the Control Board: Checking the Resistors.
Some of the power mosfets have a 100-ohm resistors across their gates. These resistors sometimes also blow up with the mosfet and go open circuit. They are close to the mosfet, usually right in front. Check all these 100-ohm resistors (marked ‘101’) the following way: after replacing the blown mosfet, connect the DMM probes across both ends of the resistor and look for a reading of about 0.100 or near. If there is no reading, the resistor is open circuit and must be changed. Take your time because if you miss a faulty one, that mosfet blows up instantly again when powering up the board.
Step 8: Repairing the Control Board: Checking the Diodes
With the DMM still set to the Diode-check range, check each one of the large Power Diodes on the other side of the board (see pic) the following way: Connect the DMM probes to each end of the diode and look for an open circuit indication (no indication) or a diode indication (an indication of somewhere between 0.4 and 0.6). Then reverse the probes and check for the opposite indication to the one before. If any of the DMM readings indicate a short, or an open in both directions, the diode is faulty; and must be replaced. Check all power diodes. I never found any of the smaller diodes faulty, but if all else fails to repair the board, you will need to check these too. On the last repair, all four diodes in the bridge configuration feeding the electro caps had blown, all cracked open, and part of the PCB track had vaporized.
Step 9: Firing It Up.
Re-assemble the Control Module and put it back in its place with the holding screw. Re-connect all the wires, paying particular attention to the 2 ground spade connectors and the mains connector. Do not re-attach the pressure sensor hose at this stage. Turn around the Control panel so that it faces the right way up and place it just lose in its place on top of the Control Box.
Now stand back and plug the mains plug in. If all is well, the control Panel should light up, ‘sing’ and settle on the last known washing cycle. Success!!!
If it fails again, you will hear a faint ‘Plop’ and you will have to start all over again because you missed one or more faulty components. Be thorough this time (it happened to me the first time because I had missed one open circuit 100-ohm resistor).
When all goes well, unplug the mains cord and, if there is no water in the machine, re-attach the pressure sensor hose and the clip.
If there is water in the machine, you will need to remove it from the machine before re-attaching the pressure sensor hose or the machine will think it is empty when in fact it is not and will overfill with more water causing a mess.
Step 10: Failure Troubleshooting.
When you first look at the board you wonder...What could be faulty here??? ...but I was so far lucky that replacing the Fuses, the Mosfets and the diodes was all I needed to get it going again, with one exception: the time it stopped because the off-balance microswitch (fitted under the Power Module, see pic) was broken and had to replace it. I found this fault by following the indication of the Fault Codes given in the manual. I bet most of the faults are due to just these parts.
If the module didn’t work the first time, check it over again. If all those Power Mosfets, Diodes, resistors and fuses are okay, the module should work because very rarely any of the other components on the board go faulty.
The water pump is now beginning to make some bearing noise, but my Fisher and Paykel is still going strong to this day.
Step 11: List of Materials
For this repair you will need:
A Philips screwdriver,
Long nose pliers,
A digital multimeter
A small soldering iron
A solder sucker
10 x 1.6A / 250V / T / 20mm fuses (slow-blow fuses) (Farnell p/n 112-3127 ) (about $10)
10 x 4A / 250V / T / 20mm fuses (slow-blow fuses) (Farnell p/n 1123135 ) (about $10)
10 x 100-ohm SMD resistors (Farnell p/n 933-5749 ) (about $5)
10 x FCD4N60 Power Mosfets (Farnell p/n 132-4776 ) (about $10)
10 x BUK98180 Medium Power Mosfets (Farnell p/n 176-9680 ) (about $10)
20 x BTY78 Avalanche Soft recovery Power Diodes (Farnell p/n 165-1070 ) (about $10)
These quantities ensure you have plenty for more than one repair, saving time as well (four in my case, and I did my last in less than an hour).
Step 12: Conclusion
The question remains…why do the Power Mosfets blow up? (the other components blow up only as a consequence). In my opinion the first event that happens puts a strain on some of the other Mosfets, which in time also fail. But why do they fail in the first place?
I am investigating this at the moment. The best explanation I can find is that under some circumstances when the machine is stopped half way through a microcontroller’s program execution (for instance when the machine is stopped with the POWER button instead of using the PAUSE button), some Mosfets are left activated out of sync and blow up. To control this situation I have now instructed ‘management’ to stop or change programs only using the PAUSE button. This has so far worked well.