Interior Lighting Circuit Upgrades and Repair on 12 Volt RV Systems

• distribution panel and harness repair
• the wider 12 volt house system

• awning motors, sensors and their wiring

• how module scanning is billed and credited

Load survey of the existing lighting

Every fixture is counted and its draw established, so the reduction from a conversion is a number the owner can see rather than a claim.

Voltage measurement under load

Readings are taken at the battery and at the furthest fixture with realistic loads running, which is the only way voltage drop shows itself.

Ground path testing

Drop across the return path is measured separately from the supply path, because a corroded ground produces symptoms that look like everything else.

LED conversion with matched dimming

Fixtures and dimmers are specified together, so a conversion does not leave an owner with lights that buzz on every dimmer in the coach.

Conductor upsizing on long runs

Where drop is the cause, the run is repowered with heavier gauge or from a nearer distribution point rather than compensated with brighter fixtures.

Distribution panel inspectionwhere applicable

Fuse sizing, bus condition and terminal tightness at the WFCO or Progressive Dynamics panel are checked while the system is accessible.

Multiplex node diagnosiswhere applicable

On Firefly and OneControl coaches, network scanning identifies whether the fault is a node, a switch or the fixture itself.

1. 1

   Establish the actual complaint electrically

   0.5 to 1.5 hours

   Dim, flickering, intermittent and dead are four different faults with four different tests. We reproduce the symptom with the coach on battery and again on shore power, because the difference between those two states narrows the cause faster than anything else.

2. 2

   Measure supply and return separately

   0.5 to 2 hours

   Voltage at the battery, voltage at the fixture, and drop across the ground path, all taken with load applied. A system that reads fine at rest and collapses under load is telling you about conductor size or a corroded connection.

3. 3

   Scan the network where one exists

   1 hour minimum

   On multiplex equipped coaches the control system gets interrogated before any panel comes off. A node that has dropped off the network explains a dead fixture instantly, and it saves hours of chasing wiring that was never faulty.

4. 4

   Correct the circuit, then the fixtures

   1 to 8 hours

   Grounds are remade, undersized runs are repowered, and connectors that have heated are replaced. Only after the circuit is sound do we address fixtures, because good fixtures on a bad circuit behave exactly like bad fixtures.

5. 5

   Convert, dim and verify

   1 to 6 hours

   LED fixtures and compatible dimmers go in together. Each circuit is then run through its full dimming range and checked for flicker, audible noise and interference, with the coach on battery rather than plugged in.

• Lights at the rear of the coach dimming when the water pump or the furnace fan starts
• An LED fixture that flickers or shimmers at anything below full brightness
• A buzzing or whining noise from a dimmer switch after an LED swap
• One fixture that works on shore power but not on battery
• A light that comes on by itself or fails to respond to its wall switch
• AM radio or antenna interference that appears only when certain lights are on
• A warm switch plate or a discoloured wire at a fixture connection
• Several lights on one circuit going out together while the rest of the coach is fine

• Voltage drop over long 12 volt runs, which is the defining constraint of a low voltage system in a 40 foot vehicle and shows first at the fixtures furthest from the panel
• Corroded ground connections behind wall panels, where a 12 volt system that grounds through the chassis loses its return path and every symptom becomes intermittent
• Pulse width modulation dimmers designed for filament loads driving LED replacements, which produces flicker, buzz and radio frequency interference
• Low quality LED replacement bulbs with no proper driver, which are sensitive to the voltage swing a house battery produces between full charge and depletion
• Fixtures wired with connectors that were adequate for original current but have loosened and heated over years of vibration
• Multiplex control faults on Firefly and OneControl equipped coaches, where a non responsive light is a network or node problem rather than a lighting problem

• 12 volt LED replacements for 1141 and 1156 bases, plus direct replacement puck and dome fixtures
• Constant voltage 12 volt LED tape and constant current fixtures with matched drivers
• LED compatible rotary and touch dimmers with drivers rated for low current loads
• WFCO and Progressive Dynamics distribution panels, blade fuses and bus hardware
• Firefly Integrations and Lippert OneControl multiplex nodes, switches and harness components
• Marine grade tinned copper wire in 14, 12 and 10 gauge with heat shrink terminals

• Fitting higher output bulbs at the end of a run that dims. The problem is voltage arriving, and asking for more current from a conductor that is already dropping makes the drop worse.
• Assuming an LED bulb that flickers is defective. On a dimmer built for a filament load, most driverless LEDs will flicker, and swapping brands until one behaves is a long and expensive way to avoid changing the dimmer.
• Tapping a new fixture into whatever wire is nearest behind a panel. Circuit loading and fuse sizing exist for a reason, and an unplanned tap tends to be discovered by a blown fuse at an inconvenient moment.
• Pulling fixtures apart on a multiplex coach before scanning the network. A node that has dropped off will explain the fault in minutes, and dismantling trim first simply adds hours to the same answer.

The complaint I hear most is that the bedroom lights go dim when the water pump runs, and people always want to talk about the lights. It is never the lights. That is a conductor at the far end of a long run with more resistance than the circuit can afford, and once you add another load the voltage arriving at the fixture falls off. I measure at the battery, then at the fixture, with the pump cycling. Once an owner sees those two numbers side by side, nobody asks me about brighter bulbs again. You fix the wire or you move where it is fed from.

Why do my rear lights dim when the water pump starts?

Voltage drop on a long run. The fixture furthest from the distribution panel already receives the least, and starting another load pulls system voltage down further. The fix is heavier conductor on that run or repowering it from a closer point, not brighter bulbs at the end of it.

Why does lighting bill at a higher rate than the rest of the interior work?

Because it is circuit work from the mechanical and electrical department at $260 per hour rather than the body rate. It is diagnosed with a meter, repaired with conductors, terminals and grounds, and performed by a different technician than the one doing cabinetry and flooring.

Is a full LED conversion worth doing on an older coach?

For anyone spending nights off shore power, generally yes. An incandescent 1141 draws around one and a half amps where an LED equivalent draws a fraction of that, and across twenty five or thirty fixtures an evening's consumption changes noticeably. Heat at the fixture also disappears, which the lens and wiring appreciate.

My new LED lights buzz on the dimmer. Are they faulty?

Probably not. A dimmer built to chop a filament load produces pulses that an LED without a proper driver reproduces as buzz, flicker and sometimes radio interference. Change the dimmer to an LED rated unit or fit fixtures with built in constant current drivers. Swapping bulb brands rarely helps.

My lights work sometimes and not others. What causes that?

Most often a corroded chassis ground. A 12 volt house system returns through the body, and a degraded ground stud behind a wall panel gives symptoms that change with vibration and with whatever else is switched on. We measure drop across the return path separately to find it.

One light stopped working on my coach with the touchscreen control. Where do you start?

With a network scan, not with the fixture. On Firefly or OneControl systems the switch talks to a node rather than interrupting a wire, so a dead light can be a node, a switch or a configuration issue. Scanning takes minutes and prevents hours of dismantling sound wiring.