Dishwasher heater relay

Discussion in 'General Electronics Chat' started by Wils68, May 26, 2014.

  1. Wils68

    Thread Starter New Member

    May 26, 2014
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    I,m not sure if this is the right place to ask but here goes ,,my dishwasher stopped heating the water so after looking on the net I traced the fault to the heater relay on the board ,,now here's the problem ,I changed the relay bearing in mind I hVe never done anything like this before I was surprised at how easy it was and how clever I was feeling until I realised it still didn't work ,,then I did. Bit more research and found I could sort of hardwire the relay by soldering a piece of wire across the relay and hey presto hot water ,now the downside to this is that the live feed for the heater comes from the on / off switch which means the heater is now permanently on ,so even when there is no water the heater will be glowing away which isn't too safe ,,,so my query and one I,m hoping someone here may be able to help me with is ,,is there anything else on the board I should be looking at that activates the relay ,,hope this makes sense to someone out there ,,thnx in advance and look forward to hearing from someone
     
  2. pwdixon

    Member

    Oct 11, 2012
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    Sounds like you've just wired the relay out of circuit which at least shows that the heater is still working.

    The relay will be controlled by some activation signal from perhaps a processor or a timing/sequence control device, that's where the original problem is I would say.
     
  3. Wils68

    Thread Starter New Member

    May 26, 2014
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    Hi and thanx for getting back to me ,,Is that something I could look for test and replace or is it a hammer job ,my missus wants a new one I want some fishing gear and can't afford both
     
  4. pwdixon

    Member

    Oct 11, 2012
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    I would trace the signal back from the relay coil but I've got many years of electronics experience, it depends on your experience/knowledge level and what tools you have eg DVM.

    One saving factor is that if it's a micro-controller problem then it 's most likely something connected to its input rather than the controller itself. So it's not that the controller can't activate the relay but more likely it doesn't think it needs to.

    Alternatively if it's a mechanical controller/timer then simple mechanics might be quite find the answer.
     
  5. Wils68

    Thread Starter New Member

    May 26, 2014
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    I changed the thermostat but that didn't work I can only check the wires from thermostat to the board and see if there is a break ,,after that I,m stumped
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    First obvious step would be to post the make and model of the appliance.
    Second step would be to locate and post the circuit schematic. Sometimes it is posted on the wall or back of the appliance.
     
  7. #12

    Expert

    Nov 30, 2010
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    True. Our complete lack of knowing what brand or model it is, how it's wired, what it uses for a timer, surely stops us from knowing the right answer.
     
  8. John P

    AAC Fanatic!

    Oct 14, 2008
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    Well, if you think the choice is fix the dishwasher yourself or buy a new one--have you considered calling a repair service?

    For what it's worth, it seems to me as if you've proved that the relay most likely wasn't bad, because putting in a new one didn't fix the problem. So it must be that the circuit that drives the relay is bad, and that could be any of several things, one of which you've already thought of--the wire between the thermostat and the relay. I have to say (speaking as an electronic engineer with many years of brilliant success behind me) my own dishwasher failed, and after a lot of tinkering around with no result, I called a repairman. He immediately diagnosed the problem as several broken wires in the area where the cable harness flexes as the door opens and closes; he said that's a common area of failure in dishwashers. I'd been assuming it was some component or connector, but I was wrong. So if I were ever faced with electrical problems in a dishwasher again, it's now the first place I'd look.

    By the way, running a heater element without control sounds like a dangerous thing to do. This could start a fire, and then your wife will really be annoyed with you.
     
  9. #12

    Expert

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    I have many funny stories about wildly over educated engineers trying to fix an appliance. :D

    The first problem is that engineers are taught everything once, so they think each part is as likely as the next to fail. Repairman quickly figure out this is not true.
     
  10. MrChips

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    Oct 2, 2009
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    I don't do repair service for a living but I am often called upon by friends to fix broken electronics.

    The most recent failures: Traynor battery operated guitar amp not working, ebike batteries not charging. In both cases, the fault was broken wires in the battery charger cabling.

    Lesson: Look for broken cables and connections first before replacing components.

    Two more examples:

    Paper shredder #1: Motor doesn't run. Problem: plastic tab that presses on the micro-switch is broken.

    Paper shredder #2: Motor doesn't run. Problem: shredder is jammed with too much paper.

    i.e. look for the easy fixes first.
     
  11. #12

    Expert

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    Opposite example: Structural engineer with a clothes washer that does nothing. He thinks he should replace the power cord. I go looking for a bad interlock switch. Presto! Bad lid switch blows safety lock-out fuse.
     
  12. John P

    AAC Fanatic!

    Oct 14, 2008
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    Well, we do pick up certain experience that might mislead us. If you install wires in a piece of equipment, you might find the wires broken at the connectors (hand-made crimps can fail easily enough, and it's definitely a place to check) but you wouldn't often encounter wires breaking in mid-run. But the wires in a dishwasher are flexed repeatedly at a single point, and subjected to a lot of vibration too, so it's apparently a weak area. This sounds as if the engineers who design those things haven't done their job properly. When something is designed right, it lasts for decades, and then every part of it fails at the same time!
     
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  13. MrChips

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    Almost true. But parts don't fail at the same time. The first part to fail fails first.:rolleyes: Then the rest fails soon after.:mad: (We know what you mean.)

    My car appears to be at that stage where one thing goes after another.
     
  14. #12

    Expert

    Nov 30, 2010
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    I do repair service for a living, but electronics is my ace in the hole.
    The designers keep changing how things are built and I can keep up with them while the average Joe gets lost. He ends up in the same place as I do, changing the board, but he often doesn't know why, and if he has any brains, it puzzles him. I know why, and that gets me to the final answer much quicker.
     
  15. MrChips

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    It bugs me dearly that we have become such a throw away society. But it is not entirely the consumer's or manufacturer's fault. (We have discussed planned obsolescence at length in another thread.) We have made the manufacturing process so efficient that it is cheaper to throw out a broken device than to repair it.

    I wish we would consider every piece of metal and plastic being thrown away as a valuable piece of resource that required a lot of chemicals and energy to produce.

    (Apologies to the OP for taking this way off track.)
     
  16. sheldons

    Active Member

    Oct 26, 2011
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    Make and model required , without that information I cannot help as my all seeing crystal ball has been sent off to an online repair and recalibration centre .......
     
  17. Alec_t

    AAC Fanatic!

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    That's from the customer's viewpoint; not the manufacturer's/salesman's :).
     
  18. wayneh

    Expert

    Sep 9, 2010
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    Me too. My folks grew up on farms during the Depression and could not help but pass along the do-it-yourself, save everything mentality that had ensured their survival.

    It seems goofy to me that many sit idle and unable to find work or even get training that might help them get a job, while their neighbors throw out heaps of items that need little or no work to be restored to normal function. We seem happy to pay the trash man to take it all away but as a society we're unwilling to pay the low skilled to be in the fix-it business.
     
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