So this happened:





What now?

You've got three problems to deal with:

1) Why did it fail catastrophically? Until you answer that, you've potentially got another set of fried components or a fire on your hands.

2) The control box - From a quick look, the relay (looks like for the heater element) overheated, enough to possibly damage the PCB.

3) The wiring harness connector is shot

On (2), my conservative nature would be to replace the entire unit. The apparent discoloration of the PCB doesn't give me a lot of confidence. If someone with more experience with repairing this kind of failure than I has less concerns, weigh their opinion. At a minimum, both the relay and the connector would need to be replaced.

On (3), you'll likely need to source both the connector body and at least new crimp pins for those that have melted. You'll likely need a special tool to crimp those pins. I have used the Engineer brand (Japan) PA-09 (1.0-1.9 mm) and PA-20 (1.6-2.3 mm) with good success. Between those two it will depend on what the proper size is for the pins. My guess is the larger one, if it is large enough. Past that, there's the PA-21, which I haven't used (I have their PAD kit as well, but I recall it being rather expensive).

Given the failure, I'd guess whatever that relay drives is the problem as there are multiple points of failure. The wire's not burned. It's like something was pulling too much current and heated up the PCB trace, which melted the solder at both ends and then it went really bad. Looking at it I'd assume that you need to replace both connector halves, and note that getting the one on the board out without the proper tools is tricky. I'd probably also add a piece of wire over the burnt trace in case it's been damaged. It's possible the relay was hurt when this happened, but I wouldn't assume so. It's also possible it all started because the pin was not properly soldered to the board when it was made and there is not wrong anywhere except for the connector.

Ira

From what I can tell, it is a wire that leads to one of the temperature safety sensors on the boiler, which leads back to the solid state relay. Is there any way to tell if any of that failed? here are some more pictures:

Without getting an electrical diagram pretty hard to guess unless you are really familiar with those circuits. A burn on a PCB can be bad, but yours is relatively small. A PCB is epoxy resin/glass and the epoxy will turn brittle when subjected to high temps.. once burned that PCB spot is compromised and can powder away. On military boards that are very expensive we'd cut out the burn and put in an epoxy patch.. Quite time consuming. I don't think the trace heated up.. it looks like the interface between the connector on that second pin. Any chance you took off that connector and it did not go back together in a good mate? It certainly looks like a power-ground short and no trace there is designed to handle that much current so no sense replacing anything until you find what caused the short. If you did repair, I'd put a reasonable solid wire between the 3 pins on that trace and solder well.

+1 on what Ira said.

The second pin from the right looks like a bad solder joint. The rightmost looks a little suspect relative to the three leftmost.



If you have no experience soldering, perhaps a pal does. Tube amp lovers are often a pretty good bet.
Try to find a wiring diagram.

If you opt to repair, the two traces from the two right most PCB pins should be double bussed with solid 20ga buss wire. The traces are barely adequate for the required current in free air. Less enclosed when covered with soldermask in a box next to a 100°C boiler.

The wires in the connector are possibly OK as the jacket is not discolored or deformed.

The relay is probably OK as it would likely have discolored / distorted case if it was over temp.

Thank you, I do have a friend who solders and knows what he's doing. So should I replace the wires or was it just the control board?

I would replace both sides of the green connector and like cafeIKE said, double up those traces with some solid wire so you know they are good. It's a simple fix if you can get the connector off without damaging the PCB.

Ira

Got it. Thank you all for your input and help. Wish me luck!