How We Diagnose an RV Generator Problem
Most expensive generator repairs go wrong at the diagnosis, not the repair. Here's the process we follow at your RV.
1. Confirm the complaint
What is the generator actually doing, and when? Does it crank? Does it start and die? Does it only fail under load? Does it fail cold, or after it warms up? We want the owner's description first, because the conditions that produce the failure are what we have to reproduce.
2. Identify the model and spec
Onan generators vary significantly by model and spec number — controllers differ, fuel systems differ, and procedures and parts differ with them. Confirming the exact unit prevents an entire category of wasted effort.
3. Inspect the installation and condition
Oil level and condition, visible fuel leaks, wiring and connector condition, corrosion, mounting, air flow and exhaust. A meaningful number of faults are visible before anything is tested.
4. Retrieve available fault information
Where the controller supports it, stored fault information tells us what the controller observed. That directs the testing — it does not replace it. A code that reports an unexpected shutdown narrows the field considerably without naming a part.
5. Check the starting system
Battery condition, connections, grounds and cranking speed. Slow cranking can cause or mask other symptoms, so it's confirmed before conclusions are drawn about fuel or ignition.
6. Check fuel delivery
Fuel supply, filter condition, pump operation and delivery, and the condition of the fuel itself. On carbureted units this is also where evidence of contamination or deterioration shows up — which affects whether the carburetor needs attention.
7. Check ignition and starting systems
On gasoline Onan units, check spark, plug condition, battery voltage, starting circuits, and the related fuel-delivery system.
8. Evaluate engine operation
How the engine actually behaves: starting, running quality, stability, noise, smoke and temperature.
9. Evaluate electrical output
Voltage and frequency, and whether output remains within range as conditions change.
10. Load-test when appropriate
Some failures exist only under real power. Applying load and observing behavior is what finds them — and it's also how a repair gets verified before we leave.
11. Identify the actual failure
The goal is a specific finding supported by what was tested, not a plausible guess based on a symptom.
12. Explain the repair options
You get told what was found, what the options are, and what they cost before work proceeds. If the generator has reached the point where replacement makes more sense than repair, we say that too, and we can discuss refurbished RV generators.
We diagnose the system instead of simply throwing parts at the symptom. It costs less and it holds up.
What it costs
The Mobile Generator Service Call is a $475 minimum. It includes dispatch to your RV within our 50-mile Tampa service area and up to the first hour of on-site diagnostic/repair labor. A 3.5% card convenience fee applies. Additional labor, parts, or repairs are quoted separately before any additional work is performed. Full details are on our pricing page.
Generator diagnosis can involve fuel, high temperatures, electrical power, and carbon-monoxide hazards. If you're not equipped to perform the testing safely, have the generator professionally diagnosed.
Frequently asked questions
- Can you diagnose my RV generator at my location?
- Yes. We're a mobile service company — driveways, storage lots and campgrounds throughout Tampa Bay, within roughly 50 miles of Tampa.
- How long does a generator diagnosis take?
- It depends on the symptom. Intermittent faults and load-related failures take longer than a straightforward no-start, because the condition has to be reproduced before it can be identified.
- Do I get an explanation before the repair?
- Yes. We explain what was found and what the options cost before any repair work proceeds.
Related articles
Cranks But Won't Start
The starter turns the engine over, but it never fires and runs.
Read guideOnan Code 36
What the controller is actually reporting — and what it isn't.
Read guideDies Under Load
Runs fine until the air conditioner or microwave comes on.
Read guideFuel Pump & Carburetor Contamination
Why a failed fuel pump can send debris downstream and put the carburetor at risk.
Read guideStill Having the Problem?
If your generator is still cranking, surging, shutting down, or refusing to start, we can diagnose it at your RV. Mobile generator service calls start at $475 and include dispatch plus up to the first hour of on-site diagnosis/repair labor.
Call 813-245-1931Mobile service throughout the Tampa Bay area