Interior Lighting in Lake Forest, CA

House lighting in a coach runs on the 12V direct current bus fed by the battery bank and the converter. That bus is not a stable twelve volts. It sits near eleven and a half when the batteries are getting low, sits around twelve and a half at rest, climbs to fourteen and a half during a bulk charge, and can spike higher during an equalization cycle or when a generator picks up. Any lighting product installed in a coach has to tolerate that entire range continuously. Products sold for automotive twelve volt use frequently do not, which is why owners see brand new LED bulbs fail in weeks.

The second twelve volt reality is voltage drop. Current in a direct current circuit loses voltage over the length of the run in proportion to the conductor gauge, and RV lighting runs can be long. A fixture at the far end of a fifth wheel is at the end of a considerable amount of wire, and if the original circuit was sized for a pair of incandescent bulbs it may be marginal for anything you add to it. When we add fixtures we calculate the load and the run rather than assuming the existing circuit has room.

Circuit protection lives at the distribution panel, usually a blade fuse per branch. Before we add anything to a circuit we check what else is on it and what it is fused at. Adding an under cabinet run, a pair of pendants and a strip of toe kick lighting to a branch that was already carrying the galley ceiling is how a fuse starts blowing intermittently on a hot day and nobody can work out why.

Older coaches use wedge base and bayonet incandescent bulbs in ceiling domes and reading lamps. Those draw a great deal of current for the light they produce and they make real heat inside a plastic fixture. A full LED conversion is the highest value electrical upgrade available on an older coach: house battery consumption for lighting drops dramatically, which directly extends how long you can sit without shore power, and the fixtures stop cooking their own lenses.

Doing it properly means more than buying bulbs. Direct replacement lamps have to be rated for the full voltage range and have to physically fit inside the dome without touching the lens, because an LED that is thermally choked inside a sealed fixture fails early even though it makes less heat than the bulb it replaced. On fixtures where the original lens has yellowed or cracked, replacing the whole fixture with a modern low profile unit gives better light and a better look than a new bulb in an old dome.

Color temperature consistency is the detail that separates a good conversion from a cheap one. Coach lighting is usually a warm white in the region of three thousand kelvin, and a mixed bag of bulbs from different suppliers will read as one room lit by three different colors. We specify a single color temperature and a decent color rendering index across the whole coach, and we convert everything at once rather than a fixture at a time, because a half converted coach looks worse than an unconverted one.

Dimming on a twelve volt direct current circuit is usually done by pulse width modulation, which switches the supply on and off very rapidly and varies the ratio. An incandescent filament does not care, because it has thermal inertia and simply glows steadily. An LED responds instantly, so if the switching frequency is low or the driver in the lamp is not designed for it, you see flicker, you get a buzz from the driver, or the lamp refuses to light at low settings.

The fix is to match the lamp to the dimmer rather than hoping. Either fit lamps with drivers rated for pulse width modulation dimming at the frequency your controller uses, or replace the dimmer with one designed for LED loads, or both. There is also a minimum load issue: many older dimmers need a certain current to regulate correctly, and after an LED conversion the circuit may draw so little that the dimmer behaves erratically at the bottom of its range.

On 120V circuits the same class of problem appears with residential dimmers and non dimmable lamps, plus one that is specific to coaches. A modified sine wave inverter produces a waveform that some LED drivers and most electronic dimmers dislike, which shows up as buzz, flicker or premature driver failure when you run on inverter and not when you run on shore power. If a symptom appears only on inverter, that is the first thing we test.

On a growing share of newer coaches the light switch on the wall is not connected to the light. It is an input to a control system that carries commands over a data bus to a module that actually switches the circuit. Firefly, Lippert OneControl and similar systems all work this way, and they are why an owner can control lighting, slides, tanks and awnings from a touchscreen or a phone. It is a genuinely good architecture and it changes how lighting work has to be approached.

Practically, three things follow. You cannot swap a multiplexed switch for a conventional one, because the switch is a low current input rather than a power path. Adding a fixture means adding it to a module output that has capacity and then configuring the system so the new load is addressed, not just splicing into the nearest wire. And a symptom that looks like a lighting fault can be a bus fault, a module fault or a configuration issue, which is diagnosed by reading the system rather than by testing a wire with a meter.

We work through the system rather than around it. Where a coach has a multiplexed control system, added circuits are assigned to real outputs with the capacity checked, and the configuration is documented so the next person to touch it knows what was changed. Bypassing the system to hardwire something in is possible and it is almost always the wrong answer, because it removes the load from the coach's own monitoring and creates a circuit nobody will find later.

Factory coach lighting is generally one thing: a set of ceiling domes that are either on or off. That produces flat, shadowless light that makes a small interior feel smaller and makes every surface look the same. The single biggest improvement available in an interior remodel has nothing to do with materials. It is putting light in more than one place and being able to control each one separately.

The layers that work in a coach are consistent. Ambient light from the ceiling, kept dimmable so the coach can be bright in the morning and low in the evening. Task light where work happens: under the overhead cabinets onto the counter, over the sink, at the desk, and at each side of the bed for reading. Accent light that grazes a surface: valance uplighting, a strip over a slide fascia, toe kick lighting that makes a floor read as continuous. Exterior facing light at the entry so the step is visible.

Under cabinet and cove lighting deserves a note on mounting. Adhesive backed LED tape fails in a coach, and it fails specifically because of heat: the adhesive softens in a closed vehicle in summer and the strip drops. We mount strip lighting in an aluminum channel with a diffuser, mechanically fastened, which also removes the dotted look of bare emitters and gives the light a finished appearance. The channel doubles as a heat sink, which extends the life of the emitters.

A dead light is one of four things: no supply, a bad ground, a failed switch or a failed fixture. Testing in that order finds it quickly and testing in the wrong order wastes hours. We start at the distribution panel with the fuse and the branch, then check for supply at the fixture with the switch closed, then check the ground, then check the fixture itself. A surprising share of coach lighting faults are ground faults, because grounds in a recreational vehicle are frequently made to a screw in a wood member with a ring terminal that has corroded.

Intermittent faults get treated differently and they are the ones that matter most, because an intermittent connection generates heat. Lights that flicker over bumps, work when the fixture is pressed, or come and go with temperature are telling you there is a loose or corroded connection somewhere, and the correct response is to find and repair it properly rather than to wiggle it until it works. We look at connectors, at splice points made with insulation displacement connectors, and at anywhere a wire passes through a metal member without a grommet.

Where a whole zone is dead, the fault is usually upstream: a fuse, a distribution panel connection, a converter output, or on a multiplexed coach a module or a bus problem. Diagnostic time runs at the posted rate with a one hour minimum and it is credited back against an authorized repair, so the time spent finding the fault is not time you pay for twice.