Custom Converted RV Repair for Owner Built Coaches
Written by RV Systems Lead, RV Systems and Electrical Lead, OCRV Center. Reviewed by Claims Coordinator
In shortA one off conversion has no build sheet and no RVIA seal, so every repair starts with reverse engineering. The house to frame mounting and the undocumented wiring are where the real risk sits.
Can a custom converted RV be professionally repaired?
Yes. Custom conversion repair means documenting what the builder actually did, then repairing to a standard. Our Yorba Linda shop handles box truck and toterhome conversions for Rancho Santa Margarita owners, covering house to frame mounting, undocumented wiring and structure that was never engineered as an RV.
- There is no build sheet, so the first job is mapping the build
- House to frame mounting is the most common structural shortcut
- Wiring follows whoever did it, not a published standard
- Insurance classification is often the owner's biggest exposure
- Base vehicles
- Box truck, toterhome, stripped chassisFreightliner, International, Isuzu and Ford medium duty are the common donors
- Certification
- No RVIA sealNo build sheet, no certified LP install and no published twelve volt standard
- First step
- Documented build mapDiagnostics at $285 per hour, one hour minimum, credited against an authorized repair
- Common shortcut
- House bolted or U bolted to frameRigid mounting to a frame that flexes, with no isolation
- Structural rate
- $210 per hourElectrical and systems work at $260 per hour
Last verified
Custom conversions arrive in every possible condition. Some are better engineered than anything a production plant ships, built by someone who understood load paths and wire gauge and did the work properly. Others are a plywood box screwed to a truck frame with lamp cord running through it. The two look similar in a photograph and nothing about repairing them is the same.
What they share is the absence of documentation. There is no build sheet, no RVIA seal, no certified LP install record and no wiring diagram, so the first hour of any job on a conversion is spent establishing what is actually there rather than repairing anything.
Make sure this is the right page
Note
A custom converted RV is a living space built into a vehicle that never left a factory as an RV: a box truck, a toterhome, a stripped chassis or a trailer shell. A coach shell converted by a professional coachworks is a bus conversion and has its own page, and a school bus build is a skoolie.
The first deliverable is a map, not a repair
On a factory coach we look up a schematic. On a conversion there is nothing to look up, so we build the document ourselves: where the shore inlet lands, what feeds the panel, how the house ground is established, which circuits are shared with the chassis, where LP runs and how it is penetrated, and how the box is attached to the frame.
That is billed as diagnostics at $285 per hour with a one hour minimum, credited in full against an authorized repair. Owners occasionally resist paying for information rather than parts. In practice it is the least expensive hour on the job, because every alternative involves opening panels speculatively and guessing at gauge and grounding.
- Trace and label every house circuit back to its source
- Identify shared chassis and house grounds
- Locate and photograph LP routing and penetrations
- Establish how and where the box attaches to the rails
How the box is attached is the structural question
This is the single most common serious defect we find. A commercial truck frame is a flexible structure by design. Bolt a rigid living box down hard to the rails and the box becomes part of the frame's torsional path, which it is not built to be. The result is a split at a wall to floor corner, usually just behind the cab where the twist is highest.
Correcting it means introducing compliance: a subframe, isolation mounts, or a mounting pattern that allows relative movement while still restraining the box. That is fabrication work rather than a repair, and it is the difference between fixing the crack and stopping the crack from coming back.
Before you proceed
A crack behind the cab at a wall to floor corner on a conversion is a mounting problem, not a panel problem. Repairing the panel alone guarantees a repeat.
Undocumented wiring and shared grounds
The signature fault on a conversion is an interaction: a light dims when the pump runs, an inverter faults when the engine starts, a fridge trips only on shore power. Those are grounding and gauge problems, and they are invisible if you test one circuit at a time. They only appear when the system is mapped as a whole.
We separate chassis and house grounds properly, size runs for the actual load rather than the connector that happened to be available, and rebuild the distribution panel with labelling that the next technician can read. Electrical work bills at $260 per hour, and on a conversion the honest majority of the first visit is tracing rather than replacing.
What we will not do on a conversion
We will not return a vehicle with an LP installation we know is unsafe, and we will not repair around one. If the propane routing is unprotected through a penetration, or a fixed appliance is unvented, that gets corrected or the appliance gets disconnected. There is no version of this where we hand back keys and mention it in a note.
We also will not certify a conversion as RVIA compliant, because that is not something a repair facility can confer. What we can do is document what was corrected, to what standard, with photographs, which is genuinely useful to an owner talking to a carrier or a buyer later.
Rates and how a conversion estimate is built
Structural, body and fabrication work bills at $210 per hour with body supplies at $5 per body hour. Electrical, plumbing and appliance work is $260 per hour. Diagnostics and mapping are $285 per hour with a one hour minimum. A written estimate is $150, credited in full against an authorized repair.
Conversion estimates carry more teardown and access time than factory coach estimates, and we show it as its own line. That is not padding. On a unit where the water heater may be behind a bonded panel and the panel may be behind a bed platform, reaching the component is frequently the majority of the job.
Who owns conversions and what they usually need
Two patterns. Owners who built the vehicle themselves and have hit something outside their skill set, usually structural or LP related, and who are generally excellent to work with because they know the build intimately. And second owners who bought somebody else's project and inherited decisions they cannot see.
The second group needs the mapping document more than the repair. We have had Rancho Santa Margarita owners arrive with a chased electrical fault and leave with a labelled panel, a corrected ground and a document, which then made every subsequent job on the vehicle cheaper.
How a custom converted is built
| System | What it is |
|---|---|
| Wall system | Anything from a commercial box body with FRP skin over hardwood posts, to plywood sheathing on timber studs, to insulated composite panel. Wall to floor and wall to roof junctions are the builder's own detail rather than a factory extrusion |
| Roof system | Commonly a translucent or aluminum commercial box roof retained as built, sometimes a membrane laid over new decking by the converter, occasionally a raised or re-skinned roof with a fabricated splice band |
| Chassis | Medium duty commercial: Freightliner M2, International 4300, Isuzu NPR or a Ford F series cab chassis, with the original leaf or air suspension, air or hydraulic brakes and the commercial GVWR unchanged |
| Typical length | 20 to 40 feet |
| Typical GVWR | 14,500 to 33,000 lb |
What typically goes wrong on this vehicle
House structure cracking where it is rigidly mounted to the frame
A truck frame is designed to twist. Factory RV builders mount a house through a subframe or with isolation. Converters very often bolt or U bolt the box straight to the rails, so the first winter of driveways transfers frame twist directly into a wall to floor junction that has no capacity for it, and the corner splits.
How we repair itIntermittent electrical faults nobody can trace
Conversion wiring is frequently unlabelled, mixed gauge, spliced under cabinets and shared between chassis and house circuits. A fault that presents as a light flickering when the water pump runs is usually a shared ground or an undersized run, and finding it requires mapping the whole system rather than testing a single circuit.
How we repair itWater entering at a self detailed roof to wall junction
Factory coaches use an extruded and gasketed corner moulding that has been through a validation programme. A converter typically closes that junction with an aluminum angle and a bead of sealant. It works when new and fails at the corners, and because the junction is also the structural connection there is usually rot behind the leak by the time it shows.
How we repair itLP and appliance installations that will not pass an inspection
Certified LP work needs correct line routing, protected penetrations, proper venting and a pressure test. Owner built installs commonly miss the venting and the penetration protection because they are the least visible parts. This is the one area where we will not simply repair what is there and hand the keys back.
How we repair itCabinetry and appliances mounted into non structural sheathing
In a factory coach a wall cabinet lands on a stud or a bonded insert. In a conversion it is frequently screwed into thin plywood between studs, which holds fine in a driveway and works loose over a few thousand miles of highway vibration. The failure often takes the sheathing with it rather than just backing out.
How we repair itWhat common jobs run on this vehicle
Build documentation and systems mapping
$285 to $2,500
1 to 9 labor hours at $285 per hour, diagnostics, scan and programming.
- Sales tax of 7.75 percent applies to parts and materials. Labor is not taxed.
- Credited in full against an authorized repair. On an undocumented conversion this is the deliverable everything else depends on.
House to frame mounting correction with isolation
$2,500 to $14,000+
12 to 60 labor hours at $210 per hour, body and paint.
- Parts at $100 or less carry 100 percent markup. Parts over $100 carry 35 percent. Special order parts require a full non refundable deposit at order.
- Sales tax of 7.75 percent applies to parts and materials. Labor is not taxed.
- A 50 percent deposit is taken at authorization on any job over $2,000, with an additional 25 percent when parts arrive on any job over $10,000. Final balance is due at pickup.
House electrical rewire and panel rebuild
$400 to $4,500+
2 to 18 labor hours at $260 per hour, mechanical and electrical.
- Parts at $100 or less carry 100 percent markup. Parts over $100 carry 35 percent. Special order parts require a full non refundable deposit at order.
- Sales tax of 7.75 percent applies to parts and materials. Labor is not taxed.
Roof to wall junction rebuild and reseal
$750 to $8,500+
4 to 40 labor hours at $210 per hour, body and paint.
- Body supplies at $5 per body hour.
- Parts at $100 or less carry 100 percent markup. Parts over $100 carry 35 percent. Special order parts require a full non refundable deposit at order.
- Sales tax of 7.75 percent applies to parts and materials. Labor is not taxed.
- A 50 percent deposit is taken at authorization on any job over $2,000, with an additional 25 percent when parts arrive on any job over $10,000. Final balance is due at pickup.
Interior rebuild to a repeatable standard
$1,500 to $50,000+
20 to 250 labor hours at $210 per hour, body and paint.
- Parts at $100 or less carry 100 percent markup. Parts over $100 carry 35 percent. Special order parts require a full non refundable deposit at order.
- Sales tax of 7.75 percent applies to parts and materials. Labor is not taxed.
- A 50 percent deposit is taken at authorization on any job over $2,000, with an additional 25 percent when parts arrive on any job over $10,000. Final balance is due at pickup.
Will it fit in the shop?
Conversions come in at every size from a twenty foot Isuzu box to a forty foot toterhome, and they all fit our doors and booth. The complication is that we frequently cannot predict where anything is. A factory coach has a known service access plan; a conversion may have the water heater behind a bonded panel and the breaker box under a bed platform. We build extra teardown time into the estimate for that reason and photograph every panel we open so the interior goes back correctly.
Insurance considerations for this vehicle
- Classification is the biggest exposure on a conversion. Many carriers write these as commercial trucks, which values the vehicle and ignores the living space entirely, so a fire or collision pays out on a box truck and not on the build inside it.
- Photograph and inventory the build now, before anything happens. On a one off conversion there is no build sheet to reference and no MSRP to compare against, so the owner's own documentation is the only evidence of what existed.
- Work performed by the previous owner is not a claim. Carriers exclude faulty workmanship, and on a conversion the faulty workmanship exclusion covers a great deal of what actually goes wrong. Correcting it is an owner expense and it is better to know that early.
Appendix: questions and answers
- Why do I have to pay for diagnostics before you fix my conversion?
- Because there is nothing to look up. A factory coach has a schematic and a service manual. Your vehicle has whatever the builder did, unlabelled, so the first hour produces the map that every later decision rests on. It bills at $285 per hour and credits in full against an authorized repair.
- My conversion has split at a corner just behind the cab. What caused it?
- Rigid mounting. Truck frames twist by design, and if the living box is bolted straight to the rails it becomes part of that torsional path. The highest twist is just behind the cab, so a wall to floor corner splits there. Fixing the panel without adding compliance to the mounting guarantees it returns.
- A light dims whenever my water pump runs. Is that dangerous?
- It is a symptom worth chasing. Interaction faults like that are usually a shared ground or an undersized run rather than a failing component, and they stay invisible if you test circuits individually. We map the whole system, separate chassis and house grounds, and size runs for the real load.
- Will you work around a propane install you think is unsafe?
- No. If LP is routed unprotected through a penetration or a fixed appliance is unvented, it gets corrected or the appliance gets disconnected before the vehicle leaves. We will not repair adjacent to a hazard and mention it in a note, and we say this at the estimate stage rather than at pickup.
- How should a home built RV conversion be insured?
- Get the classification confirmed in writing. Many carriers write conversions as commercial trucks, which values the chassis and ignores the living space, so a loss pays out on a box truck. Photograph and inventory the build now, because there is no build sheet or MSRP anyone can reference later.
Open a file on this repair
Tell us the vehicle, what happened and whether a claim is open. We will tell you what the scope looks like and what it takes to get you back on the road.
Or call (949) 799-3387