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Whirlpool dryer heater failure

Took it apart tonight. It was easier than I expected. Unfortunately, the next step, the diagnosis, was harder than I expected. So, a bit of humble pie; I though that understanding the electrics would be the easy bit.

Three wires: black, red, and brown come from the controller to the element. The red and black go to little devices which might be thermal cut-outs mounted on the side of the element. If they are cut- outs then it is a puzzle that they are in both lines. The outputs from these devices go the element itself. The brown goes directly to the same element terminal as the red indirectly goes. What's going here, is the brown a feedback to the controller so that it knows whether the cut-out is passing current? But, if the other one failed it wouldn't know.

Now the real puzzle. I don't know the power of the element but I would guess at least 1kW and at most 3kW. So (at 240V), the resistance should be a dozen or so ohms. However my meter thinks the resistance is infinite even on the 20MOhm setting. So, this would suggest the element is dead. However, the meter cannot detect any voltage between any pair of the red, black, and brown wires. Surely there are not two simultaneous faults: the element dying and something wrong in the controller? A final explanation is that the controller runs the motor for some time before sending power to the element. Is this likely? I ran the dyer for about a minute with the meter connected to the red and black wires.

-- Sean Ó Leathlobhair

The (little devices) are thermal cutouts, they are usually for different temps being for low and high and have different temp ratings printed on them, if you only have 1 drying temp 1 could be a safety cutout, if you have the 2 temp there is a safety thermo somewhere else in the circuit. also quite often there is a switch in the motor that controls the power to the heater element which may fail at times, they are used so that the heater won't operate if the motor/fan isn't working ( another safety feature). Also when you tested for power at the element was the timer set at the "Cool down" position where the motor/fan will operate without the heater to allow the clothes to cool down to avoid wrinkling. Having such a high resistance in the element indicates the element is faulty tho. Good luck and leave a message if you still have problems. (semi retired appliance tech)

Reply to
Only Just
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What's the element look like? A long coiled wire or is it sealed? If it's just a coil, the failure should be obvious.

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Reply to
Sam Goldwasser

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Thanks. I didn't see your reply directly, only as quoted by Sam.

The little devices have what may be part numbers but not obvious temperature ratings. They both have a resistance of zero (as fas the meter can tell).

We tried the voltage test on a variety of settings. We started new programs so it should not have been in cool down mode. Do you know if the controller may delay the power to the heater until the motor has been running for some time? Or might it be clever enough to notice a problem and cut the power? The purpose of the brown wire still puzzles me, it seems to be some sort of feedback to the controller so it can detect that one of the cut-outs has blown.

A faulty motor sensor makes some sense in the circumstances but it could be hard to trace without a schematic diagram. Would it be an integral part of the motor?

Thanks.

Unfortunately, it is sealed in a casing and it is not easy to see the element directly. I may be able to open the casing for a look but not necessarily in a non destructive fashion. It is held together with rivet like devices.

Another test would be to hook the element directly to the mains and see if it started to get hot. Unless my meter has gone completely mad, or it is not a simple resistive device, it would seem that it won't.

So now, the tricky question is whether to buy a new element for =A335 without being sure that it will fix the problem. On the other hand, it would probably cost at least that much to call out a professional just to look at it.

-- Sean =D3 Leathlobhair

Reply to
=?ISO-8859-1?Q?Se=E1n_O'Leathl

Thanks.

A possibility of course but touching the meter leads together reads a fraction of an Ohm or zero if pressed firmly together. It also r reads zero when I check the cut-outs. It is a fairly cheap (not dirt cheap) digital multi-meter and I doubt that it is very accurate but I don't expect that it will mistake 0 and infinity.

The terminals of the heater element seem nice and clean. So clean that I did not think of cleaning them up but I will do that to be sure.

-- Sean =D3 Leathlobhair

Reply to
=?ISO-8859-1?Q?Se=E1n_O'Leathl

Open circuit heating elements are very common. Disconnect any wires at the ends of the element and check its continuity. Should read about 20 Ohms. If it does then the fault is probably elsewhere.

--
Regards:
              Baron.
Reply to
Baron

Thanks. That is the test that I have done and the meter insists that the resistance is infinity even on the 20MOhm setting. So, this does seem to say that the element is dead. The puzzle is that the controller does not seem to be supplying any voltage to the element suggesting a second fault.

I think that I try to open up the element's casing, it may be destructive but I don't have a lot to lose. If it is obviously dead then I will have to hope that there is not a second fault and buy a new one.

-- Sean =D3 Leathlobhair

Reply to
=?ISO-8859-1?Q?Se=E1n_O'Leathl

Thanks. I didn't see your reply directly, only as quoted by Sam.

The little devices have what may be part numbers but not obvious temperature ratings. They both have a resistance of zero (as fas the meter can tell).

We tried the voltage test on a variety of settings. We started new programs so it should not have been in cool down mode. Do you know if the controller may delay the power to the heater until the motor has been running for some time? Or might it be clever enough to notice a problem and cut the power? The purpose of the brown wire still puzzles me, it seems to be some sort of feedback to the controller so it can detect that one of the cut-outs has blown.

A faulty motor sensor makes some sense in the circumstances but it could be hard to trace without a schematic diagram. Would it be an integral part of the motor?

Thanks.

Unfortunately, it is sealed in a casing and it is not easy to see the element directly. I may be able to open the casing for a look but not necessarily in a non destructive fashion. It is held together with rivet like devices.

Another test would be to hook the element directly to the mains and see if it started to get hot. Unless my meter has gone completely mad, or it is not a simple resistive device, it would seem that it won't.

So now, the tricky question is whether to buy a new element for £35 without being sure that it will fix the problem. On the other hand, it would probably cost at least that much to call out a professional just to look at it.

-- Sean Ó Leathlobhair

Be careful if you try to power up the heater outside of the dryer as the outer metal sheath can become live as they often short internally to the outer sheath as earth. Look carefully on the inside of the dryer too as sometimes there is a schematic glued to 1 of the covers, The switch in the motor that operates the heater etc is usually a mechanical weighted thro-out switch that operates when the motor reaches a reasonable speed, it can often be seen inside the end of the motor housing and can be dismantled and repaired. If dismantling the motor mark the housings well as to relocate them back EXACTLY as they were. Hope this all helps anyway.

Reply to
Only Just

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Thanks for the tip. I don't expect that the element has shorted to its casing since the casing was earthed and the chassis was not live and no fuse or trip blew. However, it does not hurt to be careful and I won't touch the device while it is powered.

Thanks for reminding me to look for a schematic inside the casing. I have not noticed one but I have not looked thoroughly. I had forgoten that was a possibility.

Dismantling the motor is moving further out of my comfort zone but if it gets to the stage that the whole machine may be scrapped then I will have a go on the nothing to lose principle. It would be a shame to dump the machine since it is not very old and looks to be generally in good condition.

-- Sean =D3 Leathlobhair

Reply to
=?ISO-8859-1?Q?Se=E1n_O'Leathl

Since you have confirmed the the heater is O/c, a simple test is to connect an ordinary light bulb in place of the heater. If you have another circuit fault it will be obvious because the bulb will fail to light.

--
Regards:
              Baron.
Reply to
Baron

Sorry missed this bit. Don't try to remove the steel outer jacket, its full of an unpleasant white powder.

By the way where in the UK are you ?

--
Regards:
              Baron.
Reply to
Baron

That's an idea. But if it can light the bulb then the meter should have detected the voltage. However, it would probably be easier to run a longer test using a bulb than the meter.

Thanks for that.

Midlands, a bit south of Birmingham.

-- Sean =D3 Leathlobhair

Reply to
=?ISO-8859-1?Q?Se=E1n_O'Leathl

Very often a meter can mislead you !

I'm 100/120 miles north of you near York. Daughter live in Brum though.

Anyway back to the plot. :-) I don't know that particular machine, but I agree with another poster that said there may be a safety circuit connected with the motor. I have never seen one though !

Commonly the motor will have three wires feeding it. One of them should be earth. That one will be connected to the case of the motor and indeed to the cabinet of the whole machine and in turn to the big pin on the mains plug.

So lets check where the power is going. Use your meter on the continuity setting and connect the black meter lead to the right hand pin on the mains plug. Trace the neutral/blue wire into the terminal box where it enters the machine. You should get continuity to that point.

Tell me what you find.

--
Regards:
              Baron.
Reply to
Baron

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Also double-check the voltage scale on the meter by probing the mains directly. Reconfirm the reading at the element terminals once you're convinced the meter is working correctly. Try the lightbulb test as well - perhaps the controller has a current sensing feature that shuts down the voltage if the element is open or one side shorted to earth (for the latter, that would explain why there's no breaker trip).

TM

Reply to
tonym924

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Good ideas. In resistance mode, the meter seems to be working but I will take some of the others' suggestions about cleaning the contacts just in case. I have not used it to measure large AC voltages for a while so a fault is possible. If the controller has a current sensor then I wonder if a bulb will draw enough to trigger it.

I am not sure if I will get time to work on it tonight so there may be no more news for a couple of days.

-- Sean =D3 Leathlobhair

Reply to
=?ISO-8859-1?Q?Se=E1n_O'Leathl

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As expected no time for the job on Thursday night. Friday night, I just could not consider the job, it would probably not be safe while drinking. Due to another problem, we have not TV at the moment but we managed a nice game of cards which goes well with drinking.

Saturday morning, I attacked the job again with a range of tests as suggested. The first test was to strap a 240V bulb over the heater contacts and run the machine. It came on but after a delay. I guess that there is some sort of motor sensor (I did not get as far as looking at that) and the controller is waiting for confirmation that the drum is turning before supplying power. So, my meter test may have failed because I was not patient enough (I did wait a bit in case of such a delay) or there is yet another test and it does not supply power to an open circuit.

So, together with the infinite resistance of the heater (terminals have been cleaned and the meter checked with some other loads), there is not much doubt of the problem now and I will be ordering a new heater element.

I will post later when I have the element and hopefully the dryer is working again. Thanks everyone for your help.

-- Sean =D3 Leathlobhair

Reply to
=?ISO-8859-1?Q?Se=E1n_O'Leathl

,
,

According to a colleague there is a thermal device in the door mechanism!

--
Best Regards:
                     Baron.
Reply to
Baron

"Se=E1n O'Leathl=F3bhair" wrote:

Odd but the lint trap is just below the door so maybe it is not so strange. Now that I have seen power applied to the element, I am reasonably happy that a dead element is to blame. I have ordered one and I expect to get it Tuesday. So, we can hope for nice dry clothes Tuesday night. Fortunately, the weather has turned nice and we can use traditional low-tech drying on the line at the moment.

The element cost me =A335 but if it gives me a few more years out of the machine, it will be money well spent. The machine looks solid and in good condition otherwise.

-- Sean =D3 Leathlobhair

Reply to
=?ISO-8859-1?Q?Se=E1n_O'Leathl

e:

I got the new element today as expected. For interest, I measured its resistance and got the plausible reading of 26Ohms. It went in easily and better still it works. The only thing wrong is that I have lost one screw but there are so many holding the back panel on that I think it will hold together with one missing.

Thanks again everyone for your help.

-- Sean =D3 Leathlobhair

Reply to
=?ISO-8859-1?Q?Se=E1n_O'Leathl

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