Saturday, 30 November 2013

Dishwasher repaired - house fire averted

A few days ago I decided to have another look at our Bosch dishwasher (in the house, this is, not the boat). It had been temperamental, and then it stopped working altogether with, apparently, no mains getting through to where it was needed.

Well, that wasn't quite the case. I removed the door panel and found that there was mains voltage there all right, but on the neutral side as well as the "live" side. Hmm. This is like the situation in low voltage circuits when a component fails to work owing to a poor return connection.

I needed to look at the plug. After clearing the saucepans and washing up liquid bottles from the cupboard next to the dishwasher I could, partly with the aid of a mirror but mostly by using my camera, see where it plugged in.


The plug was only half-way home. The live pin must have been making contact, but not the neutral pin. Let's hope the earth was connected! I reached in and found that the plug was stuck to the back of the dishwasher.

By pulling the machine forward a little, and levering, pushing and pulling on the plug, I managed to free it from the black goo on the back of the dishwasher - some sort of sound deadening tarry substance, I suppose.

Once I'd got the plug free I could see that the neutral pin was heavily corroded. The plastic insulation from around the base of the pin had melted off.

When originally installed, the dishwasher must have been pushed hard against the mains plug. This must have slightly dislodged the plug. At some point things started getting hot - very hot - probably from the poor contact between the neutral pin and the socket, and the plug body and the back of the dishwasher melted together. In its temperamental phase the means of getting it to switch on was to push hard against the door near the selector switches. I now realise that all this was doing was temporarily forcing the neutral pin to make contact with the neutral connection in the socket, but it was also rocking the machine and pulling the plug out.

The cure was as simple as cutting off the old plug, wiring up a new one and plugging it in to the adjacent socket so that it was clear of the back of the machine. Done. Switched on - and the light came on. I just knew it would work (but I still loaded it up and let it wash it to be sure).

So it wasn't the selector switches after all.

I suspect that the black stuff on the back of the dishwasher is flammable. Hmm again. And phew! No amount of protection by fuse or circuit breaker would have prevented this potentially disastrous situation.


jim macc said...

hi have you checked the Bosch web site to make sure your dishwasher i not on the list about having a manufactures fault ours was Bosch sent out a engineer and repaired free of charge the Bosch dishwashers were on watchdog.

Halfie said...

Jim, yes, I did check, and no, it isn't on the list. The fault had nothing to do with the actual dishwasher.

Alf said...

I realise that you plugged the new plug into the adjacent socket, but would it not be prudent to remove the dishwasher & inspect the connections to the socket to make sure that the heat has not damaged the fixed wiring ?

Halfie said...

Alf, you're probably right. It's possible that the insulation could have hardened and cracked. I ought to have a look.