Electrical and Systems
RV 12V DC and 120V AC Electrical Diagnostics and Repair
Typical range
$285 to $5,000+
Shop hours
1 to 20+
Labor rate
$285/hr
The short answer
Electrical diagnostics traces 12V DC and 120V AC faults on RVs, vans, trailers, and fleet units, including dead circuits, parasitic draw, converter failure, and corroded grounds. Diagnostic time is $285 per hour with a one hour minimum, refundable as a credit against an authorized repair. Repairs run $285 to $5,000 and up.
01
What this work actually involves
Twelve volt DC and 120 volt AC live in the same coach and share a chassis ground, which is why an RV electrical fault rarely stays inside one system. A converter that has lost a diode leg pushes ripple onto the DC bus and cooks the house battery within a season. A corroded ground strap between the chassis rail and the house frame makes the water pump run slow, the interior lights dim on one side of the coach, and the refrigerator control board throw a code, all at the same time. Chasing those three symptoms separately burns hours and fixes nothing.
Southern California produces its own failure patterns. Coastal air in Newport Beach, Long Beach, and Oceanside puts a green bloom inside every crimp and under every battery terminal, and a connection that reads 12.6 volts with no load will collapse to 9 volts under a 30 amp draw. Low desert heat above 115 degrees in Palm Springs, Indio, and Palm Desert bakes insulation brittle in any wire run through a hot rear compartment. Units parked on gravel storage lots pick up rodents, and rodents go after the loom behind the refrigerator first because that is the warm spot.
We start with a load test, not a meter reading on an idle circuit. Voltage with nothing running tells you almost nothing about the condition that actually fails. Diagnostic time is billed at $285 per hour with a one hour minimum, and that minimum is refundable as a credit against an authorized repair. You get the finding in writing with photographs of the failed connection or component before we price anything, so the repair decision is yours and it is made on evidence.
Systems and brands we work on: Progressive Dynamics, WFCO, Magnum, Xantrex, Victron.
Location: All work is performed at our Yorba Linda facility. We do not offer mobile, roadside, or fleet route service.
02
What the job includes
- Load-tested 12V DC circuit tracing from battery through fuse panel to device
- 120V AC branch circuit testing, breaker panel inspection, and polarity verification
- Converter and power center output testing under load, including ripple measurement
- Parasitic draw isolation circuit by circuit with a clamp meter
- Chassis to house ground bonding inspection and correction
- Corroded terminal, crimp, and lug replacement with sealed connections
- Rodent damage assessment and loom documentation for a claim
- GFCI, breaker, and receptacle testing and replacement
- Shore cord, inlet, and pedestal connection inspection
- Written findings with photographs before any repair is priced
03
When you need this service
- Interior lights dim or flicker when the water pump or slide motor runs
- House batteries go flat in storage over three to four weeks with nothing switched on
- One side of the coach loses 12V while the other side works normally
- Breakers trip on shore power but the same loads run fine on the generator
- A burning or hot plastic smell near the power center or a receptacle
- Chewed insulation, droppings, or nesting material found in a compartment
- Voltage reads normal at rest but drops hard the moment a load comes on
04
How we do it, step by step
- 01
Intake and symptom mapping
We record exactly what fails, when, and under what load. Half of RV electrical faults are described wrong by the time they reach a shop, so we reproduce the failure ourselves first.
- 02
Ground and bond verification
Chassis to house bonding and every ground lug is checked before anything else. A bad ground imitates a dozen unrelated component failures and sends people down the wrong path.
- 03
Source testing under load
Converter, battery bank, and shore inlet tested with real current flowing. We measure voltage drop across each connection rather than reading open circuit voltage.
- 04
Circuit isolation
Fuse panel and breaker panel worked one circuit at a time with a clamp meter to isolate parasitic draw or the branch carrying the fault.
- 05
Documented findings
Photographs of the failed lug, chewed loom, or burned board, with the measured numbers attached, sent to you before we quote the repair.
- 06
Repair and retest
Connections rebuilt with sealed terminals and correct gauge wire, then the whole circuit is re-loaded and re-measured to confirm the drop is gone.
05
Pricing and posted rates
| Item | Rate or range | Notes |
|---|---|---|
| Typical job range | $285 to $5,000+ | Varies with extent of damage and parts availability |
| Shop hours | 1 to 20+ | Quoted after teardown, not before |
| Diagnostics, scan and programming labor | $285 per hour | 2026 posted rate |
| Parts | 100% markup under $100, 35% over | Special order parts require a non refundable deposit at order |
| Deposit | 50% at authorization over $2,000 | Additional 25% when parts arrive on jobs over $10,000 |
| Sales tax | 7.75% on parts and materials | Labor is not taxed |
Insurance billed jobs may be billed at carrier negotiated labor rates that differ from the posted retail rates above. See all posted rates.
06
On the insurance side
Rodent damage to wiring is claimable on most comprehensive policies. We photograph the chewed loom, nesting material, and every affected circuit so the claim is supported by evidence rather than a description.
07
Vehicles we do this work on
Vehicle
Class A Gas Motorhomes
A Class A gas motorhome is a flat-front coach built on a Ford F53 or Workhorse front-engine chassis, typically 28 to 38 feet. Rear
Vehicle
Class A Diesel Pusher Motorhomes
A diesel pusher carries a rear-mounted diesel on a raised-rail air ride chassis, usually 34 to 45 feet with full-body paint and pa
Vehicle
Class C Motorhomes
A Class C is a coach body built onto a cutaway van chassis with a sleeping or storage cabover extending above the factory cab. Tha
Vehicle
Standard Fifth Wheels
A fifth wheel couples to a hitch in the truck bed through a kingpin and pin box, with a raised forward bedroom over the truck. The
Vehicle
Travel Trailers
A travel trailer tows from a ball hitch behind the tow vehicle rear axle on an A-frame tongue, which makes it the most sway-prone
Vehicle
Sprinter Vans
Mercedes Sprinter vans run last-mile routes, trade service, and camper conversions across Southern California. Sliding door tracks
Vehicle
Bus Conversions, Prevost and Marathon
A Prevost, MCI, or Van Hool conversion is a commercial motorcoach shell finished by a second-stage builder such as Marathon, Feath
08
Questions about 12v and 120v electrical diagnostics and repair
Frequently asked questions
How does the diagnostic charge work?
Diagnostic time is $285 per hour with a one hour minimum. If you authorize the repair we found, that diagnostic charge is credited back against the repair invoice. If you decide not to proceed, you keep the written findings and photographs and owe the diagnostic time only. We do not guess at a cause over the phone.
Why do my house batteries keep dying in storage?
Almost always parasitic draw or a converter that is no longer charging correctly. Propane and CO detectors, radio memory, slide controllers, and inverter standby all pull current continuously, and a single stuck relay can add two amps. We isolate the draw circuit by circuit with a clamp meter rather than pulling fuses at random.
What does an electrical repair cost after diagnosis?
Repairs run $285 to $5,000 and up, or 1 to 20 plus hours at $285 per hour plus parts. A single corroded ground lug rebuilt is at the low end. A full rodent-chewed harness section behind the refrigerator and under the chassis, replaced and re-loomed, is at the high end.
My 12V works but nothing on 120V does. Where do I start?
Start at the transfer switch and the shore inlet, not inside the coach. On a unit that runs correctly on generator power but not on shore power, the fault is almost always the inlet, the cord, or the transfer switch contacts. Those contacts pit and arc, and they fail under load rather than at rest.
Do you work on 50 amp and 30 amp systems both?
Yes. We test 30 amp single leg and 50 amp split phase service, verify leg balance on 50 amp units, and check for the reversed polarity and open ground conditions that campground pedestals routinely deliver. Pedestal damage to a coach is common and it is usually visible at the inlet and the transfer switch first.
09
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Ready to move on 12v and 120v electrical diagnostics and repair? Bring it to Yorba Linda.