RV and Van Electrical Repair in Yorba Linda

Current is the reason. Running a 1,000 watt load at 120 volts draws around 8 amps. Running the same 1,000 watts at 12 volts draws over 80 amps. Ten times the current through wire that is often undersized and thirty feet long produces voltage drop, heat and connection failure in places a house electrician would never look.

That is why a 12 volt fault usually presents as something working weakly rather than not at all. Slide motors that stall halfway. A furnace that lights and then drops out. Lights that dim when the pump runs. Every one of those is a voltage drop symptom, and every one of them gets misdiagnosed as a failed component at least once before somebody puts a meter on the circuit under load.

The 120 volt side behaves like a small house. It either works or it does not, and when it misbehaves the cause is almost always upstream of the coach: a worn campground pedestal, a heat damaged cord end, reverse polarity, or an open neutral that can put the vehicle chassis at potential. That last one is a genuine safety issue and it is the reason we test polarity and ground integrity before touching anything else.

Through an automatic transfer switch, and it is one of the most commonly misunderstood parts on the vehicle. The transfer switch is a set of relays that decides which 120 volt source feeds the main panel. Shore power and generator can never be connected at the same time, so the switch physically breaks one before making the other.

Most switches prioritize the generator. Start the generator and the switch drops shore power after a short delay, then transfers. Failures show up as no power on generator, no power on shore, or a loud chatter when the relay contacts have burned. Transfer switch and shore power diagnostics run $285 to $1,500 at 1 to 6 labor hours, which makes it one of the cheaper high value repairs on a coach.

Inverters complicate this because most inverter chargers contain their own internal transfer relay. The result is a coach with two transfer points, and diagnosing which one has failed means tracing the AC path from the cord through the main switch, through the inverter, to the subpanel. That path is different on nearly every build, which is why this is diagnostic time rather than a flat rate item.

It is the most underestimated electrical problem in storage heavy regions, and Southern California has plenty of them. Rodents chew insulation for nesting material and they preferentially target soy based insulation used on much modern wiring. The damage is rarely a clean break. It is a strip of missing insulation somewhere inside a wall cavity or above a ceiling panel.

The result is intermittent faults that come and go with vibration and humidity, plus the risk of a short to structure. We trace these with a meter and a tone generator rather than by guessing, and repairs are made by cutting out the damaged section and splicing in new wire with sealed connections rather than taping over it.

Preventive work matters here. Sealing compartment penetrations, closing gaps at the chassis to house transition, and removing food and nesting material from storage bays does more than any repellent product on the market.

• Intermittent faults that change with road vibration
• Breakers or fuses that trip only in wet weather
• Chewed insulation inside wall and ceiling cavities
• Nesting debris in the generator and battery compartments
• Shorts to chassis that read as a phantom parasitic draw

A parasitic draw is current leaving the battery bank when everything is supposed to be off. Owners notice it as batteries that are flat after two weeks in storage. The trap is that a coach has legitimate always on loads: the LP detector, the refrigerator board, the radio memory, the inverter in standby and the slide controller all draw current by design.

The method is to establish a baseline draw with the battery disconnect open, then pull fuses one circuit at a time while watching the meter. When the reading drops, the offending circuit is identified. On a large coach with multiple distribution panels this is genuinely a two to four hour job, which is why it is billed at the $285 diagnostic rate rather than guessed at.

Combined 12 volt and 110 volt diagnostics and repair is published at $285 to $5,000 and up across 1 to 20 labor hours. The low end is a single circuit fault found in an hour. The high end is a full rewire of a coach whose previous owner added six circuits with wire nuts and no fusing.