07-04-2015, 10:43 AM
Bill,
Sorry about your situation....
I am going to just speculate on what happened as I have had some experience with those control boards.
In my opinion the root cause of many of the AC problems is that poorly designed circuit board. It simply is very marginal in its ability to carry the current of the compressor and fans. Any added current due to a bad bearings, high head pressure, etc puts the board in overload and bad things start to happen. The weak areas are the little lands ( the thin copper traces ) that make it a circuit board, the compressor relay, and the connectors. My boards have been highly modified with new connectors, wires soldered to the lands to help share the current, and the occasional relay replacement when they go bad.
Imagine for a moment how an old space heater works. You look in the front and see glowing red wires as the little fan pushes air across them to make you warm. Well, that is basically a short circuit as that wire is right across the mains. Why does't the breaker trip? - because the resistance of that wire is high enough to limit the current to less than the setting of the breaker. So, in your case I speculate the fault had high enough resistance to limit the current, but 1000 watts of heat in that little box will melt it down, just as your photo shows. In that process, the 12VDC signal from the thermostat got involved and blew the little 12 volt fuse shutting down the front unit which up until then were running along just fine.
I agree with you that the circuit board is a total loss. I have not looked for a source for new boards, but maybe some one else has and will comment on availability. The board is overly complicated due to the requirements places on the designer with the option for running on 30A and only power to one leg. If not for that it would have been much more straightforward and probably could have been designed with larger copper runs and not been all the trouble it has been. Russ
Sorry about your situation....
I am going to just speculate on what happened as I have had some experience with those control boards.
In my opinion the root cause of many of the AC problems is that poorly designed circuit board. It simply is very marginal in its ability to carry the current of the compressor and fans. Any added current due to a bad bearings, high head pressure, etc puts the board in overload and bad things start to happen. The weak areas are the little lands ( the thin copper traces ) that make it a circuit board, the compressor relay, and the connectors. My boards have been highly modified with new connectors, wires soldered to the lands to help share the current, and the occasional relay replacement when they go bad.
Imagine for a moment how an old space heater works. You look in the front and see glowing red wires as the little fan pushes air across them to make you warm. Well, that is basically a short circuit as that wire is right across the mains. Why does't the breaker trip? - because the resistance of that wire is high enough to limit the current to less than the setting of the breaker. So, in your case I speculate the fault had high enough resistance to limit the current, but 1000 watts of heat in that little box will melt it down, just as your photo shows. In that process, the 12VDC signal from the thermostat got involved and blew the little 12 volt fuse shutting down the front unit which up until then were running along just fine.
I agree with you that the circuit board is a total loss. I have not looked for a source for new boards, but maybe some one else has and will comment on availability. The board is overly complicated due to the requirements places on the designer with the option for running on 30A and only power to one leg. If not for that it would have been much more straightforward and probably could have been designed with larger copper runs and not been all the trouble it has been. Russ
Russ White
2016 Winnebago Vista LX 30T
#530 ( Sold )
1999 45' Double Slide - Factory upgrade 2004