My Siemens/Bosch dishwasher won't heat properly
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,