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ISE10 1606W Pressure switch question

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I have a 10 year old ISE10 1606W and recently it's been aborting washes in the middle of a program. It will sometimes spin, when spin is selected separately, but mostly not. Occasionally, it won't turn the drum at all at the beginning of a program, having initiated what seems like a half-hearted fill, and will then sit for a long time doing nothing before sometimes initiating a drain. No error codes are ever displayed - that I'm aware of - although the 1606W doesn't seem to have many anyway.

My first thought was that it wasn't draining completely and so I checked that the drain hose was completely clear and that the pump, filter and sump were clean. I found very little gunk and all of this made no difference. I then suspected the pressure switch. The pressure chamber, inlet and outlet are clean, as is the hose leading to the pressure/level switches/sensors. There are two devices connected from a 'Y' connection to the pneumatic tube: one (leftmost in photo) appears to be an analogue pressure switch that clicks when blown into and the other looks like a pressure sensor that outputs a different voltage depending on the pressure sensed - a multi-level pressure switch? Am I thinking along the correct lines and what is the best way to test both of these devices? Am I correct in deducing their functions - the two devices: one for sensing any water in the drum and the other for sensing different levels? Are they a fail-safe arrangement and does machine confusion arise when they disagree?

I'm as certain as an amateur can be that the machine is draining away properly. Once drained, I can't hear any water when I open the door and rotate the drum, and when I subsequently drain from the drain filter, I always see the same small amount that matches the sump volume below the anti-siphon ball.

The machine had been vibrating a bit (for years, ahem) on the spin and I hadn't gotten around to looking at it. The vibration was such so that it was louder and a little unbalanced at 1600 RPM and nothing to report at 800 RPM; rather than moving around the floor or anything at all dramatic. I was hoping to address that problem when this one appeared and became higher priority (a currently non-functioning washing machine). I was also concerned that the drum not turning was a tachometer problem and I'd be grateful in learning how to test for that.

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Hello. Yes both those are pressure switches. Most washing machines only have one type or the other. The big one is the old fashioned type that's been in use for probably over 50 years. The small one is the modern equivalent. As you say it works by producing different voltages at different pressures using a magnet inside a coil. I don't get the need to use 2 though. The modern one should be able to measure all the levels needed. Maybe the old type is just used as an overfill protector. Overfill protection on pressure switches used to send power to the pump if it detected too much water.

It's strange that when the washing machine aborts it doesn't produce an error code. With washing machines not having a digital display they still usually indicate error codes with lights. Does it have 3 LEDs, Ready, Wash & Spin?

 

 


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I've attached a picture of the panel. I have an Asko manual that describes a test mode. If my understanding is correct then S1 and S2 are the start/stop and open door buttons. The temperature, spin and delayed start buttons appear to be S9, S11 and S10. I need S4/S5 to enter the test mode and I don't have it unless I'm just being dim. There must be another way.

Ready, wash and spin LEDs? Around the start/stop button there are six led segments - counting clockwise from one o' clock they are: start, heating up, temperature reached, rinsing and spinning, final rinse, end. That knowledge came from an Asko service manual and seems to fit with the ISE: it isn't mentioned in the ISE instructions.

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I've now tested the pressure sensor and level switch, as best I can.

The sensor with a 5V input produced 0.6 - 3.6V output with an increasing but gentle blow. I have no idea if the pressure corresponded with the 0-30mb marked. I couldn't find a data sheet on the sensor prior to testing. If anyone ever needs to know then looking at the pressure sensor wiring from left to right in the photo above, the wiring is +5v, output, GND.

The level switch is a two-level switch. Again, if anyone ever needs to know, from the top to bottom in the photo, the pins when applying no pressure, pressure 1, pressure 2 (>1):

closed, open, open
open, closed, closed
gnd/common
open, open, closed
gnd/common (unconnected)

This leaves me wondering where to go next and hoping that it's not a pcb fault that's cropped up in the last week.

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Could a lack of or inconsistent motor control be at the root of my machine's problem? Does that have a simple root cause that I can test for? At the moment it will fill and drain but only occasionally will it progress to turning the drum and sometimes when it does turn the drum and gets on with things for half or more of a program, there are lengthy pauses and sooner or later it drains, stops and doesn't spin.

I'm baffled as I can't see the program logic and the detail of what it's trying to do at any given moment. The lack of an old style programme selector moving around and showing the progress of the wash makes it more difficult to diagnose. If only it were run by a computer and there was a log file.

In summary, it will start any given program with a fill and then it stops and waits. Sometimes the motor runs and it will progress through a program but stop at some point before spinning. Yesterday I managed to rinse and spin by breaking out of the frozen program by switching off and on and holding start/stop. Today: no spin - not even as a separate program. Often when it has paused, I can't stop programs by holding the start/stop button and so have to resort to power off/on and hold start/stop.

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Have you checked the carbon brushes (if fitted)? If it was a pressure system fault the motor would work ok on wash and rinse, it just wouldn't do the fast spin. If the motor is only working intermittently across the whole wash cycle check the brushes and all motor connections.


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Hello Andy, thanks for your help so far.

It's a three phase induction motor and so there are no carbon brushes. I removed it after seeing your question - to be completely sure and because it was the only bit that I hadn't removed over the last day. The bit is between my teeth and the dirty laundry is overflowing.

I found an old thread and maintenance note that described water leaks from the dispenser and hose from over-foaming. Inspired by this, I ensured that the drum breather hose and dispenser hose jets were clear. I even lowered the water pressure (my home borehole system runs at 3 bar) to the machine. I did this because I'd found a slight leak that I thought was coming from the dispenser to drum hose at the attachment point into the tub - thinking that the root cause of that was overloading and/or overfoaming with single dose capsules or that the breather hose was blocked. I'd seen drips of water and a small pool in the base and the leak path for this crossed over the thermistor location. I thought that I was onto a winner and checked the hoses and then removed the thermistor and it was wet. It was then time to dismantle the control panel and check all of the connections there, and measure the thermistor resistance (7 - 8 k Ohm). I then put it all back together, started an empty quick wash and the drum turned - but only for a short time and then it stopped and the program sat doing nothing. I aborted it and tried spinning and draining - the drum didn't turn on either.

My intention is to remove the motor control unit, again. I'd already looked at it and checked that there was continuity in the cabling from the MCU to the motor and that the tacho coil produced a sensible resistance (174 Ohms). The electronics required to produce a three phase supply for the motor intrigue me. My aim is to check the components that I can. I'm fine with basic electronics, soldering and desoldering but I've never been adept at spotting dry joints. There's a temptation to resolder everything. I notice that there are a number of heatsinked power transistors and a large electrolytic capacitor on the board. Is there anything on the board that is known or prone to failure and hence where I should concentrate on?

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Appliance engineers don’t repair PCBs and no parts are made available so apart from dry joints I’ve never repaired one. 


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I thought that I'd solved it. I checked the motor control board and desoldered and resoldered some suspected dry joints. With everything reassembled, the washer ran the quick wash program all the way through to the spin and the 'end' caption. I ran another program all the way through with a decent load. I then put all of the covers back on and took the infernal machine off the to-do list.

This morning, I ran another load to start demolishing Mount Washing. The program aborted around halfway through. I tried another program and it aborted to drain and returned program control back to the beginning. All the washes had been at 30 C and I'd noticed that when the machine got to the heating cycle, it skipped it. It's the heater, I thought. So, I ran a 95 C empty wash and it ran all the way through and heated the water to 95 C.

I then ran another wash at 40 C and noticed that it skipped the heating cycle again. I then began to wonder whether the machine is programmed to abort when the thermistor senses a temperature higher than 30 C when I've selected that as a temperature and whether the abort action is to drain and stop. Using this logic, I wondered whether running a cold wash would remove this temperature abort function and whether it was hyper-sensitive around 30 C. The program ran all the way through.

I'm still not sure. Perhaps I have an intermittent sensor problem that aborts washes. Could I be correct about the thermistor and the 30 C wash? Are there any other sensors that I haven't investigated in this saga?

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Is it a hot and cold fill washing machine or just cold fill only? If the former, could the temperature of your hot water be too high resulting in wash water that is already above 30°?


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It's a cold fill and I saw the heating cycle skipped on both 30° C and 40° C washes, I haven't further tested the suspicion at 50 or 60° C yet, although that could supply the temperature that the machine "thinks" it's at - if I'm thinking correctly and if it's consistent. I ran the 95° C program yesterday to check that the heating element was actually working. The hottest temperature that I measured at the base of the tub near the sump was around 85° C. The cold supply definitely doesn't get anywhere close to 30° C. It's on the same supply line as a cold tap in the same room and I can measure the temperature there.

Is it plausible that the thermistor has a lower than expected resistance at low temperature (NTC): falsely indicating a higher temperature and causing the washer to abort the wash cycle? Does the washer abort for a higher than expected temperature and does it do it by draining the water?

I ran another wash on the 'cold' temperature setting for a.n.other wash program today, thinking that logically this wouldn't try to control the temperature and so wouldn't consider aborting the wash - and it went all the way through to the end without problem. My theory is only a theory and I'm guessing at the design to fit the facts

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My theory would only work if it was a hot & cold fill washing machine. Of course you have to wonder if the temperature sensor is faulty. I would try asking at the UK Whitegoods forums as many of the engineers on their forums are ex ISE dealers and have a lot of experience with their machines.


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I've been through the range of: washes perfectly; drum turns once in either direction and then wash aborts; drum doesn't turn at all and wash aborts; back to washes perfectly.

It looks like the aborts are all connected with the motor not running and there is a risk that it is driving me potty.

Whenever I've measured the thermistor resistance, it appears just outside of the range supplied in the Asko service manual for the WM25 machines and it's consistent: whether or not the motor is running that day. Is there any other troubleshooting that I can do for what is clearly an intermittent fault?

What I haven't done but will do on the next few washes and the inevitable non-wash is measure the tacho coil resistance to see if something is happening there in respect of a possible connection problem or wire issue.

I took the control panel apart to see where all of the buttons mentioned in the service manual were and discovered that S4 is the temperature select button on my machine. This helped me to finally run the test programs. They failed when the motor wasn't turning and completed successfully when the motor was turning. I even started to think that on the control panel board there are two relays and that one was for the heating element and the other was for the motor. I could clearly hear the heating element relay click closed and open on the test program but couldn't hear the other relay. I concluded that the other was the motor relay and that I'd solved it. Wrong. When the test program next ran properly, I couldn't hear the other relay click at all. I then wondered whether that relay is the motor control relay and whether it was spending periods stuck open or stuck closed and I couldn't determine whether that would be plausible. I need to trace the connection from the control panel board to the motor board. Tenacity is a dreadful vice but when the machine works, it works perfectly and it's too good to replace.

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It may still be the pressure switch or, more likely, the pressure sensor. I measured the voltages at the pressure sensor and saw voltage variation that made sense: albeit at reversed polarity: as though it's connected (properly and as it always has been) in a -5V supply fashion. But just because there was a variation in voltage with different water levels didn't mean that the voltages were correct for the different water levels.

I've measured voltages across the motor control board to ensure that the control board was powering the motor board and that it was communicating across the four lines. I checked continuity between the control board and motor board. All appeared good. When the motor hasn't turned, I haven't heard any humming at the motor to suggest that the motor is faulty and the same voltages were still present on the motor control board.

I noticed that the pressure chamber would often remain with an amount of water in it after draining and that the level of that water didn't change by much during the fill; and particularly so during a program that has multiple fills without draining. It may have a bearing on what is going on. I can't detect any leaks in the piping or the y-branch from the pressure vessel to the switch and sensor. Perhaps there is a small hole in the diaphragm of the switch or sensor or that something is happening either to admit air or not allow the pressure chamber to return to empty - a sticking sensor perhaps that means the air is expelled through the switch/sensor on filling but cannot return because it has formed a one-way valve? I never get an overfill error on the machine but do wonder that it quite often fills by an apparently small amount.  By forcing multiple drains and resetting the pressure system by removing the tube to the pressure sensor to equalise pressure and then draining to an empty chamber again after replacing the tube, I have been able to force the machine through a program or get it to where it will commence and continue programs - or at least that's what appeared to be happening the other day. This is not a path for future happiness. The pressure system is completely free from gunk. The door opening automatic drain appears to work properly and consistently - a function of the pressure switch.

Is it possible that the motor turning or not turning is being affected by the pressure switch or sensor? Or do I just have multiple intermittent faults and it's untrackable?

Although I cleaned the sump and floating ball therein, I can sometimes hear a movement of air or water in the sump/drain hose after pump action has ceased. It lasts for 10s of seconds as though it's water in the drain hose falling back and resettling the level within the sump. The drain hose arrangement is as it should be and it feeds into a vented stand-pipe and so syphoning seems unlikely. Is there any value in running test cycles with the ball removed?

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Hello there. If there was a hole in the pressure system anywhere in the washing machine would overfill and flood. If there is a blockage in the pressure chamber that can also result in overfilling but it can also result in the washing machine not spinning. I've never heard of it resulting in the motor not working at all. The motor not working at all or just turning once or twice and then stopping for the rest of the cycle sounds much more like a fault on the main PCB or a weird connection fault somewhere. Likewise a fault on the thermistor is likely to cause overheating, which can eventually after the water has heated up too much resulting a wash cycle aborting but it would bring up an error code. If the fault is intermittent then anything that you do or change can potentially trick you into thinking you have made some difference when in actual fact all it is is that it is the nature of intermittent fault working sometimes and not others. To be honest an intermittent fault like this is just not something that you can really deal with as a DIY repair.


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