AEG oven earth leakage issue coil heating element testing tips? - Page 1
Forum section: electronics / repair

author: ESXi
author_rank: Regular Contributor
timestamp: May 29, 2020, 02:01:11 pm
content: So recently my oven stopped working. First thing I did obviously was letting it cool down unplug it to check if there weren't any obvious burnt components and reverse the thing.But the issue is. It works for a little while(always) and then when the oven is heated up a little bit the earth leakage protection kicks in.I tried to swap the live and neutral around and it didn't do much at all.There's two big heating elements, the fan motors are both brussless (checked bearings, was still fine imho).The main function switch is mechanical rotation switch like this;I measured the heating elements and they where like sth between 60 and 30 ohms. 60 for the big one and 30 for the smaller one.I called the company to verify any of my measurements but they don't tell it nor give the schematics or datasheet of the elements, nor can I find them online or by resellers.What I tried was to measure the casing to the element terminals and there should not be any leakage resistance, and in my case it was only a few k ohms.Any tips on how to properly test or measure the elements to make sure that they are bad or almost faulty. Because I don't feel like wasting 150 euros on elements if they are still fine.The wierd thing is, it works for a small amount of time before it shorts. Maybe I can trace back the wires and look what happens because then the function switch was set to a cretain position "heated air function" after it failed the live and neutral where both dead shorted and when I switched back to another mode the short disappeared..I called the company for more info, they could not give it but the nice guy in the technical support told me this is because dumb (he didn't directly say that, I made that of it but he agreed) people mess it up thus far that the oven burns down their house and the damage claim will be on them. Obviously I can completely understand this, and their reason for not giving it. But it still sucks to some point, if I knew what the elements should have had resistance wise I would have been able to easily say hey this is not good or otherwise and dig deeper down the rabbit hole.

author: themadhippy
author_rank: Super Contributor
timestamp: May 29, 2020, 02:13:57 pm
content: A live to neutral fault wont,or shouldnt ,trip the earth leakage protection,only a fault to earth.Quoteyou really need a megger,an ohmmeter that use a high voltage,to test but a few k ohms dont sound good,it should be at least a couple of 100k .In days gone by ,on new appliances ,it was common for them to initially trip the rcd due to damp getting into the element,the trick was to remove the earth and run them for a short time to "dry out" then reconnect the earth,however this is a bit dodgy, so dont try it at home kids.

author: masterx81
author_rank: Frequent Contributor
timestamp: May 29, 2020, 02:27:08 pm
content: My oven does the same sometimes. I think that is humidity that goes inside the ceramic element of the heating resistor, allowing a small current flow trough the ceramic insulation. When it give me this problem, i leave it on for 30min/1hour at 60~100°c, so that the humidity goes away, then cooling it down with the door open. I prefer a low temperature as the "on" time is not so long, so there is less chance that it trips the protection. When i do this procedure, the oven woks for months before giving other problems.Or you can change the heating element.

author: wraper
author_rank: Unknown
timestamp: May 29, 2020, 03:00:34 pm
content: QuoteHeater resistance to case in kiloohm range is 100% fault. You need insulation tester to know that insulation iscertainly fine. But what you measured is completely enough to know those arecertainly bad. In other words any further tests are redundant to verify that they are bad.

author: George Edmonds
author_rank: Frequent Contributor
timestamp: May 29, 2020, 03:23:14 pm
content: PLEASE NOTE RCD'S WILL AND MUST TRIP IF THERE IS A FAULT TO EARTH ON EITHER THE LIVE OR NEUTRAL.George

author: madires
author_rank: Super Contributor
timestamp: May 29, 2020, 03:25:14 pm
content: If the isolation resistance of the heating element is too low the heater usually needs to be replaced. There's one exception, when you use the oven very rarely (once or twice a year) the humidity inside the heater builds up and causes a low isolation resistance. In that case you can bake the heater for half an hour (disconnect the heater or put it in another oven) and check the resistance again. If that doesn't help get a new heating element.

author: shakalnokturn
author_rank: Super Contributor
timestamp: May 29, 2020, 03:36:51 pm
content: +1 with wrapper.Often if you measure in the 100k ohm range cold it isn't enough to trip the RCD, once hot that resistance decreases enough to trip.I don't know if it is due to dampness or the resistance wire getting closer to the metal container through thermal cycling.In some cases depending on how far on the resistance the leakage is from either terminal you can get away with swapping the live and neutral connections. Sometimes and for some time, it is in no case a reliable repair, either way it is a life hazard if the ground connection is broken.

author: Gyro
author_rank: Super Contributor
timestamp: May 29, 2020, 03:37:35 pm
content: Quote from: ESXi on May 29, 2020, 02:01:11 pmIf you want a bit more confidence in the diagnosis, measure the leakage to earth when the element ishotor has just tripped (It sounds as if you can simply unplug it and measure across the plug). The leakage resistance of the Alumina filling will tend to decrease with temperature, and you might just be able to catch a situation where an part of the element winding has expanded and is still in contact with the inside of its tube.

author: ESXi
author_rank: Regular Contributor
timestamp: May 29, 2020, 05:13:04 pm
content: Quote from: masterx81 on May 29, 2020, 02:27:08 pmYes I think the element is damaged or breached. I might replace them I will try this and see what happens, I think this is what has happened, I mean the oven is eleven or twelve years old now, haven't used it that much but I guess they are just degraded then.Quote from: wraper on May 29, 2020, 03:00:34 pmYea I think it's breached. The tube, and some sort of humidity or H2O went inside and this is what caused the issue. Dumb thing I did in a hurry was I took frozed patatoes out of the freezer and threw them in a cold non pre-heated oven... Whoops, I think this produced the steam which then got in the elementsI tried this and it was when the oven was completely cold and disconnected. I can try it again and report back what I measure.https://youtu.be/7SmDeNb8qdo?t=104Quote from: Gyro on May 29, 2020, 03:37:35 pmYes I will try to further dig down and look what wires go to where and see if it's only one element or if all of them are weak.

author: wraper
author_rank: Unknown
timestamp: May 29, 2020, 06:52:35 pm
content: Quote from: ESXi on May 29, 2020, 05:13:04 pmIf water can get inside the heating element trough it's sheath, it means it was already bad anyway.

author: ESXi
author_rank: Regular Contributor
timestamp: June 05, 2020, 05:45:40 pm
content: Quote from: wraper on May 29, 2020, 06:52:35 pmI am serious angry now. Guess what I tried, I tried to reproduce the problem. I took it outside (it was 23℃, almost no wind) and did the following test. I took boiling water in a pan and put it in the oven I tried all functions to produce maximum amount of steam to the elements. I disconnect each heating element one by one and did test them by letting the oven heat up with boiling water in a pan. In the same socket in the kitchen grounded. NOTHING happened, it worked perfectly fine for +1 hourToday I want to cook dinner and guess what happened. The fan started to go crazy for a bit and suddenly bang, again earth leakage protection kicked in.I really don't know what it is and since I have almost wasted perfectly fine food and my precious time it's time to ditch this f*cker.. Done with it.Elements are 207 euro for all of them, but if that's not the issue why would I waste my money then. Uhhh sorry but this is so frustrating, why not fail completly dead short, open or magic smoke, then I could at least find the problem. Now it's a deep shitty rabbit hole. I hate those types of problems. Hardest issue to hunt down, when something works but sometimes not without any f*cking clue to what it could be since everything is working until it decides to not work for whatever reason..

author: Gregg
author_rank: Super Contributor
timestamp: June 05, 2020, 07:02:39 pm
content: The elements may be the first to suspect for current leakage, but any component could be the problem. The fan going crazy might be worth a look.A dim bulb tester can be used similar to a poor man’s megger if you are careful; you’ll have to decide if you want to try this as it could become a shocking experience.I sincerely doubt that moisture getting into the elements is your problem after the boiling water testing.

author: shakalnokturn
author_rank: Super Contributor
timestamp: June 05, 2020, 07:59:55 pm
content: The odds are the element that was measuring 100 kilo ohms or so resistance with a multimeter is the one to replace...If you like messy wiring and want to be sure who the culprit is: Wire a RCD to each heater you suspect then you'll see which trips

author: xavier60
author_rank: Super Contributor
timestamp: June 06, 2020, 01:19:51 am
content: My aunt's oven had odd fan behavior. The convection fan had leakage between the bottom layer of the stator winding and the core.Oddly though there was no RCD trip.

author: ESXi
author_rank: Regular Contributor
timestamp: June 09, 2020, 04:43:46 pm
content: Quote from: shakalnokturn on June 05, 2020, 07:59:55 pmI did it the smooth brain way. I disconnected each element and tested it again, but first I let it trip the RCD (it was by the way always when the oven was between/about 190-220c with nothing in it). This time build it back in the kitchen. I found the bad element, and it was the hot air mode so the fan with the coil that makes hot air. I have disconnected it now and whatever. It works again. I might buy this element it's only 56 euro.For now, enough ovens.. I brought a new one and guess what, the quality was crap!! The legs on the bottom panel where on one side banged and smashed up. It was a horrible decision to buy a new one that was down priced from 800 to 400 euro. The oven just sucked, the control knobs where loose, the front panel was wanky loose and the complete case was messed up (bent). Really bad quality control. I'll rather fix my old AEG oven that was like 600-700 euro ~12 year old oven, way better build quality.. The shop I brought it from was by the way trustworthy. But still, don't fall for this discount scam from bol.com. by bo means did they check the device before selling it, or it was damaged during transportation. Anyhow the quality of the oven itself was NOT 800 euro original.. Can't be true..So I just packed it up (the new oven). Because I wanted to repair the old oven and build the new one in the kitchen again but since the new oven is crap quality... I will live with the old one, just made two pizzas (with top and bottom heater) and it worked so let's enjoy the pizza and forgot about the crap paperwork and waiting for my money again...

author: shakalnokturn
author_rank: Super Contributor
timestamp: June 09, 2020, 05:38:44 pm
content: Of course you chose the most logical solution by disconnecting one element at a time, I was just assuming you intended to use it "normally" when I suggested using individual RCD'sToo bad for the new oven being of less value than the old and defective one. Also a shame that you can't do some swapping and send them their junk back with a leaky element, they're probably going to trash it anyway.

author: ESXi
author_rank: Regular Contributor
timestamp: June 12, 2020, 02:40:13 am
content: Quote from: shakalnokturn on June 09, 2020, 05:38:44 pmI could do that but, whatever. I can fix my old oven that is better than those new "quality" ovens and still enjoy it a few more years before I have replace the other elements. Turns out that the heat air fan also had coil isolation issues because of too many heat and cool down cycles. In quite extreme matter because the element is failed and glowing orange.. They are rated to only last 10 to 12 years. Mine is 12 years so I ordered a new motor also and new heat element.

author: Gyro
author_rank: Super Contributor
timestamp: June 12, 2020, 10:33:18 am
content: In the days before RCDs and breakers, it used to be easy to spot defective elements because only part of the element would glow (and brighter!). Elements are definitely 'wear items'. I remember seeing top ring elements that had burned through the outer metal sheath.P.S. I dimly remember my Dad describing such elements as 'on their way out', time to think about getting a replacement!

author: bd139
author_rank: Super Contributor
timestamp: June 12, 2020, 11:01:40 am
content: Check the switch as well. This fucker nearly burned my house down...Same criminal piece of shit. 1Y old Zanussi. Everything is made of shit these days.

author: shakalnokturn
author_rank: Super Contributor
timestamp: June 12, 2020, 01:35:58 pm
content: As it is very common for the switches to heat and char, I've never seen one that looked as if it had actually caught fire (then again if it does happen either no one, the fire brigade or the insurance people get to see them).IMHO the switch is flame retardant and all wiring silicone or fibre and housed in a metal enclosure the chances of a fire propagation seem quite low.

author: ESXi
author_rank: Regular Contributor
timestamp: June 13, 2020, 12:51:45 am
content: Quote from: Gyro on June 12, 2020, 10:33:18 amFun thing is I need a thermal camera. When I tested the oven outside the kitchen it did work. But when I build it in again the oven had problems again. I think heat dissipation, inside not.. I saw the hot air element burning bright orange.. For sure this wasn't a good thing, eventually turns out he was indeed bad. Ordered a new one including original motor.

author: ESXi
author_rank: Regular Contributor
timestamp: June 13, 2020, 12:54:32 am
content: Quote from: bd139 on June 12, 2020, 11:01:40 amI did check them. What is the problem? Wearing nylon or carbon reinforced plastic or the metal contacts? Heat resistance problem I guess and production cost cutting... This is why I still like my dumb vintage power hungry quality, made to last electronics. Idk this is really bad for the environment, that's my biggest concern man. Also the way smartphones and computers go. And what these days doesn't have a computer or pcb inside. It's almost everything.Burned spade male connector like really wtf. I hope they correctly fused the element before the switches... If not the power hungry failing element could let the switch on fire because of dust in that area above the fan... This is really why we need the schematics. Don't want to take my time to reverse engineer a freaking oven in my free time got better things to do. Anyways they don't give schematics, so we have to check it and to find the fault. No proper fuse installed. How else can you burn these connectors away. They are rated for what they should do..

author: bd139
author_rank: Super Contributor
timestamp: June 13, 2020, 08:25:36 am
content: Issue with the switch here was that it was a better fuse than anything else in the unit. I didn’t check to see if there was anything else in the circuit.The picture I took there was after the thing was repaired by a repair tech. He moved the burned contacts into another contact pair. Now it’s a 13A rated oven so you can’t put the grill and main oven on at same time or it’ll overload the circuit. So I was checking it out and guess what? Put the grill on and the oven comes on as well. Idiot had no idea what he was doingErgo the entire oven was charge backed on my CC and sat in my garden for a month until they sent someone out to collect it.Alas yes stuff is junk these days. The vintage units however are usually dangerous in some other way!

author: ESXi
author_rank: Regular Contributor
timestamp: June 13, 2020, 08:40:28 pm
content: Quote from: bd139 on June 13, 2020, 08:25:36 amAh alright meh that sucks. Well about vintage stuff being unsafe, sure some equipment can be unsafe but most things that survived all these years. Not too worried about it. Not that I let these devices in standby or run when I am not at home but you get the idea. Don't know anything about vintage ovens. Most of the vintage stuff I have is audio equipment like radios, amps, active speakers, some kitchen tools like a mixer from Philips 70s. Really good build quality but no brains at all if you overload the motor it will burn down your house maybe when the person is a complete idiot. So yeah I agree, you should always use these tools with caution and a brain. New stuff these days always have a brain box inside (micro controller and sensors or feedback, current sensing or sth). So you can't smooth brain the device to oblivion lol.