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Diago
Instant AI vehicle diagnostics
Diago
Instant AI vehicle diagnostics
Diagnosing an RV is different from diagnosing a car. You have two battery systems, a chassis that may be Ford, Chevy, or Freightliner, and coach systems that can mask or cause what looks like an engine problem. Diago knows the difference.
Gas (Ford V10, Chevy 8.1) or diesel pusher (Cummins, Freightliner chassis). Heaviest, most complex. Pusher diesels have unique cooling and DEF considerations.
Van conversion — Mercedes Sprinter, Ford Transit, Ram ProMaster. Smaller engine but all the same van reliability considerations.
Built on a cutaway chassis — Ford E-450, Ram ProMaster. Common, well-supported, but the overhang body weight adds cooling and brake stress.
RVs have separate chassis and house batteries. A dead chassis battery is the #1 reason an RV won’t start, even if the interior lights work fine (those run off house batteries).
Heavy RVs climbing grades push cooling systems hard. Low coolant, a worn water pump, clogged radiator, or failing thermostat are all common culprits.
Onan and Cummins Quiet Diesel generators have their own fuel supply, oil, and air filter. Low fuel level at the generator pickup (not the dash gauge) is a frequent surprise.
Especially on gas Class A units towing a toad vehicle. The transmission cooler may be undersized from the factory for the combined weight.
Many Class A units have air suspension. Air bag leaks, compressor failure, or height sensor faults can cause a rough ride or keep the RV from leveling properly.
Hydraulic systems that power slides and jacks can fail from low fluid, bad motor, or a blown fuse. Coach won’t be safe to drive until slides are fully retracted.
Tell Diago your motorhome, year, chassis type, and what’s happening. Get an instant diagnosis — chassis or coach — with repair steps and the nearest RV shops and service centers.
Diagnose my RV →Check the chassis battery first — it’s separate from the house batteries that power your interior. Make sure the battery disconnect switches are on, check chassis battery voltage (should be 12.4V+), and confirm the emergency start relay hasn’t failed. If the chassis battery is fine, it may be a starter, fuel delivery, or immobilizer issue.
RVs are heavy and climb grades under constant load — much harder on cooling than normal driving. Check coolant level first, then watch the temp gauge on grades. Common causes: low coolant, failing thermostat, clogged radiator, or bad radiator fan clutch. Diesel pushers should also check the charge air cooler (intercooler).
Yes — RV mode covers both the chassis/engine and the living area: generator faults, LP gas systems, HVAC, water heaters, slide-outs, leveling jacks, plumbing, and solar/inverter issues.
Diago’s resources panel shows the nearest RV repair shops, campgrounds with hookups, dump stations, propane fill, and RV parts stores — so you can make a plan from wherever you’re stuck.