Dishwasher Heater problem - Zanussi DE4554

[Doug99]

My dishwasher is not heating during all cycles. I have checked that 240v is getting to the element ok when on 'wash'. Continuity resistance of the element is reading 25ohms which in normal circumstances suggests the heater is also ok.

The element is marked AC230v 2100W 791R. What is this last figure? Is it the continuity resistance for this particular heater?

Many thanks in anticipation - Doug

 

[zipper]

Ohms law (R=E2/P in this instance) states the resistance should be 25.19048 ohms. The element is good. I don't know what the last digits mean, perhaps it refers to a manufacturing code...but it certainly isn't an ohmic value.

 

[Leccy758]

How have you checked you have 240 volt to the heater element.

Most of these have a permanent 240 V supply to the element as the neutral is switched not the live. So if you have used a Neon type indicator or a volt meter measuring between the element and the chassis or a neutral elsewhere you would get 240 volt.

 

[Doug99]

Zipper / Lecky758 - I measured 240v across the element terminals using a multimeter. If the element is good then it should be working, but it isnt I'll remove it from the machine and bench test it.

 

[zipper]

NTC issue? It should measure around 6kohm at 20C with a decreasing tendency when heated. Is the machine PNC number 911788040?

 

[Doug99]

zipper you are correct the PNC is 911788040 - The heater worked ok on the bench so I refitted it and connected the multimeter permanently across the element during a wash cycle. 240v was applied for approx 1 minute and then nothing! Water still cold so obviously the feed is being isolated too early. I have removed from the sump what looks like a thermostat (NTC?) which is marked 'Type 279'. Across the thermostat I am measuring 5.6Kohms at room temp (21C) and when I heated it up in a saucepan it dropped and levelled off around 1Kohm. The water was hot to the touch (not boiling) as I did not want to cook it. If the NTC is ok, what next?

 

[zipper]

NTC sounds ok (they don't fail that often). Take out the pcb & check the soldered connections on the back side. The module on your Zanussi is exactly the same as several AEG models & I often find a blown solder point on the heater circuit on these pcb's. If you're lucky it is repairable by a careful clean-up & a new dot of solder. If everything looks/tests good then just about the only thing left is a duff pressure switch but I don't have a great deal of belief it could be that.

 

[Doug99]

Before I start ripping out the PCB, do you know if these in line heaters have any 'built in' thermostat which may switch it off? I've searched online for the heater but there is no detailed technical descriptions.

 

[zipper]

Some washing machine elements have integral fuses....not this type. But even if it did you wouldn't be reading 25 ohms anyhow. Pull out the pcb, open the plastic case & check for a blown solder point on the back of the card. It happens quite often on these particular modules. Is isn't a big job to remove.

 

[Doug99]

Is the PCB behind the door panel?

 

[zipper]

It is behind the control panel (where the buttons are).

 

[Doug99]

Managed to get back into my shed after the Xmas activities and ‘defrosted’ the dishwasher before cracking on!! Checked the PCB, no obvious dry joints but ‘touched up’ the connections with a soldering iron anyway just in case. Run a ‘cycle’ and it all appeared to work ok with the water heating up as expected.

Replaced all panels, checked for leaks and run another cycle – NO HEATER!!!! AAAARRGGGGHHH.

I give up!!

 

[zipper]

Speak to these people http://www.emwelec.co.uk/index.php?action=category&id=11 £30 to change the heater relay...or you could try to source one yourself.