Electrical faults are where RV repair bills get out of hand, because they are the easiest to guess at. A part gets replaced, the symptom moves, another part gets replaced. The way out of that is measurement.
An RV has two electrical systems, and they fail differently
Almost every confusing RV electrical problem makes sense once you know which of the two systems is involved.
The 12V side runs from your batteries: interior lights, the water pump, vent fans, the furnace, slide-outs, jacks, and the control boards inside your fridge and water heater. When 12V is weak or dying, the symptoms are strange rather than obvious — a fridge that will not stay lit, a slide that moves slowly, a furnace that clicks and gives up. Owners often chase the appliance when the fault is the supply.
The 120V side is shore power or generator: outlets, the air conditioner, the microwave, and the converter that charges your batteries. Faults here are usually more clear-cut, and considerably more dangerous to guess at.
The two are joined by the converter, which turns 120V into 12V to charge the batteries, and by the inverter if you have one, which does the reverse. A surprising share of “my batteries will not hold charge” calls turn out to be a converter that stopped charging months ago.
What a real diagnostic looks like
Voltage alone does not tell you much. A battery can read 12.6V doing nothing and collapse the moment anything asks it for current. What matters is what happens under load: actual amperage draw, voltage drop across a run, and whether the numbers match what the circuit should be doing.
*One hour minimum labor charge required with all service calls. Contact us for current labor rates.
Measuring, not guessing
A 120V diagnostic in progress.
What we take on
- 12V and 120V troubleshooting, from the pedestal to the appliance
- Shore power, converter and inverter diagnostics
- Battery testing and replacement, including lithium upgrades
- Breaker, outlet, GFCI and wiring repair
- Transfer switch and surge protection faults
- Parasitic draw — the battery that is flat every time you come back to it
For full off-grid builds — solar arrays, lithium banks and inverter/chargers designed as one system — see solar and lithium installation.
Things worth checking before you call
Some of these solve the problem outright, and all of them make the diagnostic faster:
- Check the pedestal, not just the RV. Campground power is frequently the actual fault. A low-voltage pedestal will make a perfectly healthy RV behave badly, and it can damage the air conditioner.
- Reset every GFCI you can find. There is often one in the bathroom feeding outlets you would never associate with it, and sometimes one outside in a wet bay.
- Look at the battery disconnect. More common than it sounds.
- Check the battery terminals. Corrosion and loose clamps cause faults that look electronic and are not.
- Note whether it fails on shore power, on battery, or both. That one answer narrows it enormously, and it costs you nothing to observe.
Where we draw the line
120V work in an RV deserves respect. Shore power in a wet bay, a transfer switch, or a suspect ground is not a reasonable place to learn. If you are not certain, stop — that is a completely sensible decision and we would rather come out to a fault than to a fire.
We are also an RV service company rather than a chassis shop: brakes, bearings, axles, suspension and tires are outside what we take on, including their wiring.
Our service call fee of $150 covers travel to your RV and a complete diagnostic. You get an explanation of what was actually measured and a firm quote before any repair starts.
RV Electrical FAQ
Three usual causes: a converter that has stopped charging them, a parasitic draw pulling current while everything looks switched off, or batteries that have simply reached the end of their life. They are easy to tell apart with a clamp meter and a load test, and hard to tell apart by guessing — which is why batteries get replaced far more often than they need to be.
That is the 120V side, and the two systems are separate. Start with the pedestal and the breaker, then any GFCI in the coach — there is often one feeding outlets you would not connect it with. If those are fine, the transfer switch or the shore power cord end are the next suspects.
Yes. It is worth doing properly rather than as a straight swap, though: your converter or charger has to have a lithium profile or it will not charge them correctly, and it is worth knowing whether your alternator charging and any solar controller are set up for lithium too. We size the bank to what you actually run rather than to a shelf package.
Common ones, yes — the parts that account for most faults. Anything unusual is ordered, and we will tell you at the diagnostic whether it is a same-visit repair or a return trip.
Yes, and it is one of the most damaging things in RV life. Sustained low voltage makes air conditioners and motors draw more current to do the same work, which is how they overheat and fail. A surge protector that also monitors voltage is one of the cheapest pieces of insurance an RV owner can buy.
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*One hour minimum labor charge required with all service calls. Contact us for current labor rates.