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My Siemens/Bosch dishwasher won't heat properly

Posted by martinlarsen (My Page) on
Sun, Apr 13, 14 at 8:45

Our Siemens SE36A290SK dishwasher (identical to the Bosch model, except for the name) does not heat properly. It runs for many hours before finishing because the water never gets hot, only lukewarm, and the dishes aren't clean.

At first I thought it was the infamous "Runs forever, showing 1 minute" error caused by a defective relay or soldering on the controller board, but it does actually finish the cycle after about 8 hours. The timer starts at 199 minutes, slowly counts down to say 60 minutes, then goes up again to perhaps 130 minutes and so on. Finally it counts down to 1 minute and stays there for a long time while the machine is still rinsing. Normally it would be at the end of the drying cycle now. At last it finishes, though. It also does heat, albeit not very much, and eventually the water gets somewhat warm but it takes a very, very long time.

I have replaced the relays wity no luck. Also the solderings look fine and there are no other signs of problems on the board. Then I bought a clamp meter and measured the power consumption for the heater to be around 900 mA which explains why the water does not get hot.

Do you think the heater is defective or could there be another cause?

Basically I would like to know what I should do next to locate the problem. I am familiar with fixing stuff, having electronics as my hobby.

Thanks so much in advance,
Martin, Denmark


Follow-Up Postings:

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RE: My Siemens/Bosch dishwasher won't heat properly

Have you cleaned the pressure chamber and the heat exchanger located behind the left side of your dishwasher?

Alex


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RE: My Siemens/Bosch dishwasher won't heat properly

Alex,

The pressure chamber has been the cause twice for a similar problem as described here: http://ths.gardenweb.com/forums/load/appl/msg0413510827197.html

Although the symptoms are much the same, there are differences not present this time:

- the special sound stemming from the lack of water in the sump
- the ability to help the dishwasher finishing the cycle by throwing 2-3 litres of water into it

Also, it does actually finish the cycle after 7-8 hours.

I am pretty sure the pressure chamber or heat exchanger isn't the cause this time. But I could check if you think it could be the cause even though the symptoms are different.

But what about the power consumption of the heater. At 900 mA at 230 V it consumes only around 100W. Even if the pressure chamber or heat exchanger was clogged, it would consume the same power, wouldn't it? I guest there is only a on/off function of the heater.

If not the heater itself, I am wondering if there could be a bad connection somewhere etc.

By all means correct me if I am wrong in my assumptions about how it works!


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RE: My Siemens/Bosch dishwasher won't heat properly

Yes, the heater can only be on or off. If the water level switch isn't satisfied, it won't let the heater turn on.

I skimmed the Universal Repair Manual from the German forum (only available in German) and it says:

Machine doesn't heat or gets stuck
- does is fill?
- does it drain?
- does it recirculate?

If yes -> check for defective relay.

If the relay is okay, the dishwasher probably doesn't take enough water in -> check the pressure chamber and the heat exchanger for clogs.


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RE: My Siemens/Bosch dishwasher won't heat properly

Can you give me a link to the repair manual?

Thanks.


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RE: My Siemens/Bosch dishwasher won't heat properly

Here's the General Manual and here is another one on how to clean the heat exchanger. You could also try Appliance Junk's Google Drive, which has service manuals for US Bosch dishwashers - these lack the heat exchanger, though.


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