Systems and Power

A coach carries two electrical systems and a translation layer, and most of the confusing faults are in the translation layer. The 12 volt house side runs lights, pumps, fans, control boards and slide motors off a battery bank. The 120 volt side arrives from shore power or a generator and runs air conditioning, the microwave, outlets and often a residential refrigerator. Between them sit a converter, an inverter, a transfer switch, a distribution panel and a shore cord, and every one of those is a single point that can take both systems down while both systems are perfectly healthy. An owner reporting that nothing works has usually described the middle layer without knowing it.

Sorting a symptom into a domain takes about a minute and saves an afternoon. If 12 volt things work and 120 volt things do not, look at shore power, the cord, the pedestal, the transfer switch. If 120 volt works on shore and not on the generator, it is the generator or the switch rather than the panel. If everything faded together instead of stopping, that is a bank being drained by something, and the fault is a load rather than a supply. If one circuit died alone, it is that circuit. The pattern of what still works is more diagnostic than the list of what does not.

The reason this shop charges for diagnostics rather than absorbing them is that measurement is the work. A battery bank that reads healthy at rest can collapse under load, so a rest reading proves nothing and a load reading proves everything. A converter can put out a voltage that looks correct and still not be charging. Parts swapping without a meter is how an owner spends $500 to $5,500 on a house battery replacement that was never the problem, and then spends it again. Diagnostics are $285 with a one hour minimum, credited against an authorised repair. Twelve volt and 120 volt diagnostics and repair runs $285 to $5,000, depending on how far the fault sits from where the symptom appeared.

Lithium conversions are the most common recent source of faults that nothing on the coach is technically at fault for. A LiFePO4 bank behind a converter and an alternator regime designed for lead acid accepts charge differently, reports state of charge differently to a panel calibrated for something else, and behaves differently when it is cold. House battery replacement runs $500 to $5,500, and the bank is often the least interesting part of the bill. What matters is whether the charging sources, the monitor and any low temperature protection were addressed at the same time, because a bank installed without them works beautifully for a season.

Solar behaves the same way. Solar installation runs $1,500 to $12,000 and the panels are rarely where a problem sits. Controllers, fusing, cable sizing and the roof penetrations that got the wiring inside are where both the faults and the leaks come from. Every array is also a roof modification, and on a coastal coach the sealant around those mounts joins the same six month cycle as everything else up there. More owners should hear that sentence before the array goes on rather than two winters after.

Electrical urgency does not sort by how annoying a fault is. A fault that is annoying can wait. A fault that is warm cannot, and heat is the signal that separates the two. Anything on this list is a same week booking regardless of whether the coach still works around it.

• Any smell of hot plastic, or discolouration or deformation at a terminal or plug.
• A shore cord or pedestal connection that is warm to the hand after an hour.
• A breaker that resets and trips again, which is a circuit reporting a fault rather than a nuisance.
• Battery terminals showing swelling, weeping, or corrosion growth since the last look.
• An LP or carbon monoxide detector that alarms and gets muted rather than investigated.
• A generator that runs but surges under load, which is fuel or governor rather than wiring.

Engine and chassis mechanical work is not what this shop does, and nothing here addresses it. Nor does anything here describe work performed anywhere except in the building, on a coach that arrived under its own power or on a truck. Systems faults are diagnosed with the vehicle present and a meter on it, which is a limitation worth stating because plenty of writing on this subject implies otherwise.