Bosch Dishwasher E02 error

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sparer

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I have a Bosch Dishwasher Serie 4 (SMS50C26UK/D3) that is showing E02. According to this website E02 is a Heater Relay fault. I have removed the computer from the appliance and removed the relays (there are two) from the PCB and tested them out of circuit to ensure they operate correctly. They do.

The relays are DPST and there is one for Live and one for the Neutral so Bosch have doubled up the contacts for each line.

I then soldered the relays back into the PCB and ran a cycle whilst monitoring the voltage to the coils. I can see 13.4V continuously on both relays either side of the coils. At no point do I get a 0v that would cause the relay to switch the mains to the heat pump.

Does anyone know which sensor would cause the PCB to energise the coils and switch the relays or any other advise on what is going on?

Many thanks
 
Have you resistance tested the relay contacts?
Does the heater coil show resistance?
 
When I had to play with my electrolux dishwasher I soldered some fly leads in various places with choccy blocks and ran them externally to the dishwasher so I could monitor it whilst in use.
Check the heater coil and the thermistor is working correctly. Either could also bring on the same fault?

sparer said:
Yes. they are short when coil is energised.
Click to expand...
 
Sorry just re-read your original post - If you see 13.4v on both sides of the coil and not across the coil then the relay is probably switched on the 0v side and is not being activated.
Probably new PCB time...
 
SpecialK said:
When I had to play with my electrolux dishwasher I soldered some fly leads in various places with choccy blocks and ran them externally to the dishwasher so I could monitor it whilst in use.
Check the heater coil and the thermistor is working correctly. Either could also bring on the same fault?
Click to expand...
Thanks. I'm pretty sure that the heat pump has no mains because it has to go through those relays. I'm not so sure about the thermistor though I think I would see an E11 fault if the thermistor was faulty. Shame because it's a decent dishwasher and I can't find a replacement PCB.
 
Maybe give Bosch a ring, I wonder if they could help with the codes?

sparer said:
Yeah I googled EPG70002 too but I am unsure as to what the 9001 140 272 code means as other EPG70002 units have different codes. I'm worried that its the same board with different firmware.
Click to expand...
 
Such a shame when it works out like that!
The only other way is to work out what IC the 0v of the relay coil goes to and assume its faulty...

sparer said:
I just found the correct part on the Bosch website https://www.bosch-home.co.uk/store/12015029 but it costs too much to make an economical repair. I might have risked it for 50 quid but not for £111. The dishwasher is 4 or 5 years old so I guess it's time for a new one.
Click to expand...
 
SpecialK said:
Such a shame when it works out like that!
The only other way is to work out what IC the 0v of the relay coil goes to and assume its faulty...
Click to expand...
I guess I could as it's bound to be some kind of transistor driving the relay. Trouble is, we had to do the dishes handraulicly this evening so i'm not sure that the other half will wait any length of time. I might just have another quick look at the PCB to see if I can see a transistor though. Luckily it's only one screw to get it to bits.
 
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