Electrical Repair, in detail

The most common electrical fault on an RV is not a failed component. It is voltage drop across a corroded ground. A lighting circuit reads 12.6 volts at the battery and 10.9 volts at the fixture, and the fixture is dim, the slide motor is slow, or a control board resets under load. Measurement has to happen with the circuit loaded, because an unloaded meter reading across a bad ground looks almost perfect. We measure at the battery post, at the distribution panel and at the load, then at each ground point, and the reading that collapses tells us where to work.

That is why an electrical ticket starts at a diagnostic hour rather than at a part number. The band runs from one hour at $285 to twenty hours or more at the top, and the difference is almost never the part. It is how much interior has to come apart to reach the wire. A ground stud behind a bay wall is a twenty minute repair once it is visible and a four hour job to make visible. Nothing about that is satisfying to hear, and it is exactly what the invoice reflects.

• Rested open circuit voltage and voltage under load, taken at the battery post
• End to end voltage drop on the suspect circuit with the load switched on
• Clamp meter on each branch at the distribution panel to isolate current
• Ground continuity to chassis at every screwed and crimped point on the circuit
• Thermal check of the distribution panel and transfer switch while loaded

Twelve volt work covers the battery bank, the disconnect, the distribution panel and everything downstream of it: interior and exterior lighting, the water pump, slide and jack motors, roof vent fans, furnace blower and ignition, tank sensors, step controllers, and the control boards inside the refrigerator and water heater. Nearly all of it is fused rather than breakered, and nearly all of it shares a small number of ground points, which is why one bad ground produces four unrelated complaints at once. An owner reporting that the lights flicker whenever the pump runs is describing a ground, not a pump.

Age matters here in a specific way. Coaches from the nineties and early two thousands used a great many crimped butt connectors with no adhesive lined heat shrink over them, and a coastal Orange County coach will have green copper inside those crimps. Cutting them out and replacing them with soldered or adhesive lined joints is unglamorous work billed by the hour, and it is the repair that actually holds. Cleaning the same connection twice a year is cheaper each time and considerably more expensive across five years.

A shore power complaint usually arrives described as a park problem. The owner says the pedestal is bad because the coach lost half its receptacles. A meter at the pedestal reads a clean 120 volts on both legs, so the pedestal is fine and the fault is inside. On a 50 amp coach the leading culprit is a transfer switch with burnt contacts on one leg, which is precisely why half the coach works and half does not. Those contacts arc every time the generator starts and stops, and after enough cycles one set pits or welds.

Transfer switch and shore power diagnostics run $285 to $1,500, and a burnt switch usually lands near the middle once the bay is open and the conduit is redressed. The other frequent finds are a heat damaged inlet on the coach side, a cord end that has been running warm for a year, and a neutral that was never properly torqued at the panel. Any of those produces the same symptom, and any of those will eventually cook an air conditioner compressor if it is left alone long enough.

Harness damage has favourite locations and the slide room pass through is the worst of them. Wiring for a slide has to flex every time the room travels, and manufacturers route it through a grommet that wears. Insulation chafes, the conductor eventually shorts to the frame, and the symptom is a fuse that blows only when the room is partway out. Finding that means running the slide in stages with a meter on the circuit instead of staring at the fuse block and guessing.

Fuse block and panel work is the other half of the category. Blade fuse holders lose spring tension and heat up, breakers weaken after enough overload cycles and start tripping below rating, and a panel that has been added to across three owners usually has two wires under one screw. We relabel a panel while it is open, because an unlabelled panel is the reason the next diagnosis takes two hours instead of one. Aluminium branch wiring in older conversions gets replaced rather than reterminated.

• Adhesive lined heat shrink on every joint, never vinyl tape
• Slide harness rerouted with a service loop and a new grommet at the pass through
• Blade fuse holders replaced rather than reseated when the spring has gone soft
• Panel legend written, photographed and filed with the job

Two boxes get confused constantly, so here is the plain version. A converter turns shore power into twelve volts and charges your batteries. When it dies, everything twelve volt keeps working for a while on a full bank and then slowly stops, because the bank is discharging and nothing is refilling it. An inverter turns battery power into 120 volts so a microwave or a receptacle works with no pedestal and no generator. When it dies, nothing at all changes while you are plugged in, which is why owners often discover it weeks later at a boondock site.

Replacement runs $750 to $4,500 across three to fourteen hours. Magnum, Xantrex and Victron are what we fit, and the choice is usually decided by the existing remote panel and the battery chemistry rather than by preference. A Magnum inverter charger already wired to its own remote is cheaper to keep in the family than to cross over. Victron gets specified when an owner wants the monitoring and the programmable charge profiles, and it earns that money on a lithium bank and very little of it on flooded batteries.

A combined inverter charger that has failed on the charger side only is common and worth confirming before the whole unit is condemned. Some are repairable at board level and most are not. On a unit past about ten years old, the labour to chase a board costs more than the replacement, and we will say that rather than sell the diagnosis.

A coach that kills its batteries in five days while sitting has a parasitic draw, and the only honest way to find one is a clamp meter and patience. Chassis and house sides get isolated at their disconnects, then each branch is clamped with everything switched off, and the current that should not be there gets traced back to its source. Typical finds are a stereo memory circuit wired to the wrong side of the disconnect, an LP detector that never sleeps, a step controller that stays awake, a failed board holding a relay closed, and an inverter left in standby drawing steadily around the clock.

Owners are frequently told to replace the batteries, and sometimes the bank is genuinely finished, but a new bank installed over an unfound draw dies on the same schedule. Testing first is cheaper. Two hours of clamping costs less than a set of AGMs, and if the bank turns out to be dead as well, at least it is going into a circuit that will not eat it.

Three things decide where a specific job sits inside the band. Access comes first: a fault behind fixed cabinetry or under a slide floor costs disassembly hours before any repair begins. Documentation comes second, because a coach with a real wiring diagram in the owner packet saves an hour of tracing and most coaches do not have one. Age comes third, since a system repaired four times by four people has to be understood before it can be corrected, and understanding it is billed like everything else.

Insurance work follows different logic. Electrical damage from a collision, a roof leak or a rodent intrusion is claimable and gets photographed at teardown, and a supplement is likely because water and rodents both track along a harness far past the visible damage. Corrosion, wear and a previous owner's wiring are not claimable. We separate those lines on the estimate so nobody discovers the split at pickup, which is a worse conversation than having it on day one.