Chassis or House: Which Half of the Motorhome Broke

A Class A motorhome is two vehicles bolted together. Underneath is a truck chassis with a diesel or gas engine, a transmission, air or leaf suspension, air or hydraulic brakes, and a set of truck tires. On top is a house with its own electrical system, generator, water, propane, slides, and a hundred things that can go wrong on a trip. When something fails on the road, knowing which half it belongs to is the difference between getting the right help fast and spending an afternoon on the phone.

Here is how the two systems split, what fails on each, and what a mobile crew handles wherever the coach is parked.

The chassis: everything that makes it a truck

• Engine, cooling, fuel, exhaust, and aftertreatment on diesel coaches.
• Chassis batteries, the starter, and the engine alternator.
• Transmission and driveline.
• Suspension, including air bags and leveling on the chassis side.
• Brakes, air or hydraulic, and the ABS.
• Steering, tires, wheels, and wheel ends.
• Dash gauges, chassis lighting, and the engine-side wiring.

These are truck problems and they fail the way truck problems fail. A diesel pusher with a coolant leak, an air leak, a dead chassis battery, or a blown tire is a heavy truck with a coolant leak, an air leak, a dead battery, or a blown tire, and the diagnosis is the same one in our truck repair posts. The difference is where the parts are hidden and how much bodywork is in the way.

The house: everything that makes it an RV

• House batteries, the converter or inverter, and the shore power system.
• The generator, its fuel supply, and its transfer switch.
• Slide-outs and their motors, hydraulics, or cables.
• Leveling jacks on the house side, on coaches that have them separate from the chassis.
• Propane, the water heater, furnace, and the refrigerator.
• Roof air conditioners, awnings, entry steps, and the 12-volt house lighting.

These are the systems we wrote about in RV Electrical Problems on the Road, RV Generator and Battery Issues, and Your RV Slide-Out Won't Retract. Some of them, like slides that will not come in and jacks that will not come up, stop the coach from moving at all. Others, like a dead water heater, are an inconvenience that can wait for the next campground.

The ones that cross the line

A few problems live in both halves and confuse everyone.

Batteries. A coach has chassis batteries for the engine and house batteries for the coach. They may be connected through a solenoid or an isolator that lets the engine alternator charge both, and a boost switch on the dash that ties them together for starting. A coach that will not start may have dead chassis batteries because that solenoid failed, or because a house load found its way to the chassis side. Sorting out which batteries are dead and why is the first step, and it is the same voltage-and-cable work we do on trucks.

Air. On a diesel pusher, the chassis air system runs the brakes and the suspension, and sometimes the house-side leveling and the entry step. An air leak that will not let the coach air up affects all of it. That is a chassis repair, and it is a normal roadside one.

Leveling. Some coaches level with the chassis air suspension, some with hydraulic jacks that belong to the house. A coach that will not come up off its jacks may be a hydraulic problem or an air problem depending on the system. We covered the jacks side in RV Leveling Jacks That Will Not Retract.

If the coach will not move, the first question is why. Jacks down, slide out, air not building, or engine not starting are four different repairs, and telling dispatch which one it is gets the right parts on the truck.

What a mobile crew handles

The chassis, fully, wherever the coach sits: engine, cooling, air, brakes, tires, batteries, alternators, wiring, and the mechanical side of the suspension. On the house side, the things that stop the coach from traveling: slides, jacks, batteries and charging, generator starting problems, entry steps, and 12-volt wiring. Deep coach work like appliance repair, plumbing, and bodywork is not what a roadside truck is set up for, and the crew will say so. Our RV and camper service page covers the list, and RV Roadside Assistance on I-10 covers what happens when the call comes from the shoulder.

Frequently asked questions

My coach engine cranks but the house has no power. Related?

Probably not. The house batteries or the converter have a problem and the chassis side is fine. Check the house battery disconnect switch first.

The engine will not crank but the house has power. Related?

Try the boost or battery-combine switch on the dash. If the engine starts with it, the chassis batteries are dead and the reason needs to be found.

Can a mobile mechanic work on a diesel pusher?

Yes. It is a heavy truck chassis and the same service truck and tools apply.

Do you come to campgrounds and storage lots?

Yes. Campgrounds, storage lots, driveways, and the shoulder, across the panhandle service area.

Motorhome down anywhere from Pensacola Beach to Crestview? Call Duckett Roadside Repair at (850) 495-0366. Tell dispatch which half broke and the crew comes ready. Answered 24 hours a day.