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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#41
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Whirlpool dryer heater failure
On Feb 9, 3:44 pm, Baron wrote:
Seán O'Leathlóbhair wrote: On Feb 7, 6:20 pm, "Seán O'Leathlóbhair" wrote: On 7 Feb, 18:05, wrote: On Feb 7, 10:54 am, Smitty Two wrote: In article , "Seán O'Leathlóbhair" wrote: On Feb 7, 2:28 am, Smitty Two wrote: In article , "Seán O'Leathlóbhair" wrote: Surely there are not two simultaneous faults: the element dying and something wrong in the controller? I'd be suspect of the test results. The slightest corrosion on a test lead or the DUT can cause gross errors. 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 Ó Leathlobhair Mistaking zero and infinity is a common meter problem, due to corrosion as I suggested. If the meter probes are clean, what about the connections on the machine? You're looking at a heating circuit; heating tends to oxidize metals. Did you scrape them with an x-acto or similar? The only reason I'm being a pest about this is that I agree with you that it doesn't seem reasonable in this case that you have double trouble. I'd also run a cheater cord from the wall to the heater element as a verification test. 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). 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. 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 Ó Leathlobhair According to a colleague there is a thermal device in the door mechanism! 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 £35 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 Ó Leathlobhair |
#42
Posted to sci.electronics.repair
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Whirlpool dryer heater failure
On Feb 9, 7:06 pm, "Seán O'Leathlóbhair" wrote:
On Feb 9, 3:44 pm, Baron wrote: Seán O'Leathlóbhair wrote: On Feb 7, 6:20 pm, "Seán O'Leathlóbhair" wrote: On 7 Feb, 18:05, wrote: On Feb 7, 10:54 am, Smitty Two wrote: In article , "Seán O'Leathlóbhair" wrote: On Feb 7, 2:28 am, Smitty Two wrote: In article , "Seán O'Leathlóbhair" wrote: Surely there are not two simultaneous faults: the element dying and something wrong in the controller? I'd be suspect of the test results. The slightest corrosion on a test lead or the DUT can cause gross errors. 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 Ó Leathlobhair Mistaking zero and infinity is a common meter problem, due to corrosion as I suggested. If the meter probes are clean, what about the connections on the machine? You're looking at a heating circuit; heating tends to oxidize metals. Did you scrape them with an x-acto or similar? The only reason I'm being a pest about this is that I agree with you that it doesn't seem reasonable in this case that you have double trouble. I'd also run a cheater cord from the wall to the heater element as a verification test. 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). 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. 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 Ó Leathlobhair According to a colleague there is a thermal device in the door mechanism! 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 £35 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. 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 Ó Leathlobhair |
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