July 21st, 2012
Ok, So you have a Bosch Dishwasher. You load it up, add the dishwasher detergent and start it. About 3 hours later you notice that the machine is still running. Hmmmm… you think to yourself… I don’t remember it taking this long to do a load….
Well you’re right. It should have been done 1.5 hours ago. But the reason could very well be a common issue on these machines. The water may not be heating up.
There’s a way to check this. You will need a basic clamp-on amp meter. Gain access to where the power cord goes into the machine. Slip the clamp-meter around either the hot or the neutral wires (makes no difference which but not around both)
Start the machine in a normal cycle and watch the clamp-meter. Somewhere around 8- 15 minutes in, the heater gets energized. This causes a significant jump in the amount of current being drawn into the machine. The current will jump from 2-3 amps to about 11. If this time has come and gone and all you see on the clamp-meter are 2-3 amps its a pretty safe bet the heating element isn’t being energized.
So anyway, a temperature sensor in the machine looks for a temp rise, and if it’s not sensed, it’s internal clock goes into a “holding pattern”- waiting for the water to heat up. And so, the machine runs and runs and runs… waiting for a temp increase that’s never going to show.
So what happened?
These control boards have a printed circuit that a heater relay is soldered onto. Because of the high current
going through this relay (about 11 Amps) the solder joint gets so hot the joint softens up and the solder pulls away from the connection resulting in an open circuit to the heating element.
Ok then, can I fix it?
Easy. That is, if you’re handy with some basic hand tools and a soldering iron. You need to remove the door cover, (you’ll need a #15 Torx tip) then the control panel. CAREFULLY– remove the control module (the case is made of plastic which gets brittle at it ages. It’s very easy to break the plastic switch telegraphers) Then CAREFULLY– open it up to get to the circuit board. Look closely at all the solder joints and if you find one that looks like this:
You’ve most likely found the problem. Just apply a little heat with a soldering iron and re-flow the joint.
Put it all back together and you’re in business!
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