Aeg favourit- water not heating up
AEG Favorit 40850
Problem : Water not heating.
Checking the heater
Access to the heater (tube type) is via the small rear panel. Remove two star screws, and pull the sides out SLIGHTLY to release the panel. The electrical contacts of the heater are to the inside so are not visible yet. I removed the left hose (hose compression clip) and the earth connection on the bottom of the heater. This allowed me to twist the heater round and see the electrical connector. I removed this, and measured the resistance of the heater. It was 28Ω, from reading various forums, this seems to be of the correct order, therefore the heater is ok. I put everything back together, remembering the earth connection on the bottom, and turned to the front of the machine
Checking the Relay :
Again from reading around there is a relay in the supply chain to the heater, described as ?in the door?. I opened the door and removed the crosshead screws. This released the front panel from the inner metal part. The control switches and the mains switch are held in with clips, easily removed, I guess you could leave the mains switch connected to the front panel, but I removed it so that the skin would not be pulling on any wires.
I then wrote (with an indelible pen) a number on all the connectors to the control box, noting that one of them has to be fitted at one particular end of the unit connector, as it could fit in more than one position. With the control unit removed the next step was to open it up.
The control unit is clipped together with four clips, just press them in and it opens. At this point I should say that there are proper electronics inside this box, so some sort of static protection should be observed! Ground yourself before working inside the unit, touching something metal connected to ground should to the trick (radiator, but not the painted part!), and do not touch any of the components on the board, or the connections. Be careful of the flexible connection between the two boards, do not bend it any more than necessary. The relay mentioned above is in the bottom left of the board in my extremely bad picture. Unclip the main board, and have a look around where the relay is on the other side. One of my pins was charred, and on closer inspection was not actually making contact!! Looks like it was a bad / high impedance joint that was getting hot, and finally melted the solder causing the open circuit that made the heater not work.
With a soldering iron I reflowed the solder (adding more as necessary) to make the connection between the relay pin and PCB good. This was the only visible problem, so I reassembled everything (reverse order of disassembly, Haynes is a wonderful manual!!!) and tried the machine. IT WORKED!!!
The whole process took probable less than an hour, and saved the cost of a repair man, and a new control unit (I don?t think anybody fixes things like this on a commercial bases any more, easier for them to just replace the unit!!
This is what I did to fix my water not heating problem, I am experienced with electrical and electronic components, so if you choose to follow my story please be careful, it can save a few pounds, but it?s not worth risking your life if you really don?t know what you are doing.
For interest, the relay is a NAIS device, numbers on the top are JS1-B-12V-F-H111, and AJS1311F MO1. My relay was working so I didn?t need to look for a replacement, but they should be fairly easy to find if yours is broken. Being an electromechanical device this is probably the most unreliable component in the heater chain, although if the rest of the circuit is designed correctly should last for years, if not decades. (I have seen relays used in gas boilers that had no suppression, and therefore burnt themselves out within 3-4 years, but I don?t think that is the case here)