My T12SC has developed a habit of blowing the main DC fuse (20A) whenever the battery is connected.
Now, before I hear a chorus of a thousand voices saying the battery is backwards please consider the following points. It is NOT BACKWARDS
1. It is the main 20A fuse blowing, not the reverse polarity fuse
2. When I can get the fuse to hold, all the polarity sensitive electronics (stereo, CO detector, smoke detector, LED lighting, furnace and A/C controls) work properly. The water pump and roof vent turn in the correct direction. None of these devices would work properly if the battery was backwards.
3. If plugged into 120AC first, then connect the battery, no fuse blows. If the battery was backwards, the reverse polarity fuse should still blow. It does not.
4. When I can get the fuse to hold, everything works fine even if shore power is then disconnected.
5. When I can get the fuse to hold, the charging system provides a charge to the battery. It would not if the battery was backwards.
6. I pulled ALL the fuses, except the main and reverse polarity. Still happens.
7. Breakaway switch was checked just in case. It is wired directly to the battery, so no brake current would pass through the fuse that is blowing, and the switch is open.
All devices are switched off (except smoke, CO, propane detectors and the radio memory circuit) when the battery is being connected, yet there is a bit of a spark at the battery terminal. I'm wondering if the charger has an internal capacitor and the surge current from charging up that capacitor is doing it?