(Note: I know I am posting this a month after a deadline, but I thought it is worth mentioning as I am very happy about it.)


Previous month's theme was Simple Electronic Repairs Project14 | Earn a $100 Shopping Cart for Your Simple Electronic Repairs! . I didn't have anything to repair that time, but a coworker approached me one week before Christmas, because he noticed I was talking about electronics to another colleague. He has got an almost 16-year old Vaillant CNG boiler for a heating of his entire house (including a water tank). The trouble was that a control board couldn't switch the burner properly. He did a good job examining the control board and finding out, that after knocking on one of the two relays present on the control board, the relay switches the contacts and the heater is turned on. This was his daily job for a few weeks, in fact, turning on the electronics every day after coming from work, knocking on the relay, heating the house and water (thermostat was bypassed for obvious reasons, max. output was delivered to the heating system) and switching everything off in the evening.


The servicing company said that another board (probably used) would cost ca. € 400.


I requested a photo of the board and especially the relay and their surrounding:

boiler control board relay


The relay is identified as EE Electronic E3206S (for switching 250 V, 10 A), working with 24 V DC and resistance of the coil 1100 Ohms. I haven't found a way to buy a new one from common distributors, but I found a seller on eBay that had two unused relays (probably in the past). It took about 2 weeks during the Christmas time to get it from Australia to Czech Republic.


Yesterday I visited my colleague with a soldering iron and a simple manually operated "pen style" pump and replaced both relays. I am glad the board was originally soldered using a lead solder, so I could do the work easily. I have no I idea whether I would be successful if the lead-free solder was used (need to do more research on that, I only have one bad personal experience).


vailant boiler control board

After replacing the relays and plugging everything back again, a magical moment came. The boiler started as before the breakdown.


We are both happy that we gave a meaningful life to the board again, for about € 10, saving € 390 + price of the work.


This was not the end of this evening I also repaired a toaster (burned temperature fuse soldered inside) for about €1 (new could cost ca. € 30 - 50) and rewired his house lights in one room (after a not very successful change of a power switch), so it could be switched on and off from two places.


I don't have a video, because there wouldn't be much to see, as the device is well covered and the flame is not visible.