Cummins Onan Generator FAQs

Q: Can a generator charge my RV house battery?

• A: Not directly. But a generator does provide power to operate your converter/charger, which charges batteries.

Q: Is it practical to power the roof air conditioner with my generator while traveling on the road?

• A: Yes, that is what a generator is for: portable electrical power. In fact, it can help lower fuel consumption because the generator uses less fuel than your vehicle engine. Plus, it gives you an opportunity to exercise your generator. Any appliance that can be run in a stationary position can also be powered while driving.

Q: Why does a breaker trip and one air conditioner not work when I turn it on while the generator is running?

• A: Some RVs with two air conditioners have a 20-amp circuit breaker for the rear air conditioner and a 30-amp breaker for all other loads (including the front air conditioner). The RV may be wired with the two circuits reversed, causing the breaker to trip. The generator connections and wiring should be checked at an authorized service location.

Q: Is generator power clean enough to run a laptop?

• A: Yes, with Cummins generators this is no problem. The set should be turned on and warmed up before turning on the computer. The normal precautions for home use should be followed for RV use as well.

Q: Can I operate an air conditioner and microwave at the same time?

• A: Although this is possible in lower temperatures or altitudes or with high-efficiency ACs, Cummins 2,500- and 2,800-watt generators will probably be overloaded when the AC cycles off and on with the microwave running. Load-shedding devices are available that automatically turn off the AC when the microwave starts and then restarts it when power is available again. All other Cummins generators can operate both of these appliances at the same time.

Q: Will high-efficiency (power saver) air conditioners provide more reserve power?

• A: Yes. High-efficiency ACs use 30% less power and are easier to start. That means more power is available for use in the RV or for better fuel economy. High-efficiency ACs also have higher cooling output than comparable standard ACs.

Q: What happens if I “short-cycle” my air conditioner?

• A: Short-cycling refers to stopping and restarting the air conditioner compressor before the refrigerant pressure has enough time to equalize. If this happens, one of several things can occur: a circuit breaker may trip, either on the generator or at the breaker panel; the generator engine may stall; or the AC compressor may trip its overload. AC compressors should remain off for at least three minutes before being restarted.

Q: Can I run an RV generator in a national park?

• A: Yes. Cummins-installed generators are quieter than the national park sound level requirements (during allowable hours of use).

Q: Why do I want to exercise my genset?

• A: Regular exercising of the genset heats up the alternator windings and removes or expels excess moisture. In sets equipped with brushes, exercising helps prevent corrosion buildup on slip rings. Running the genset also brings fresh fuel to the carburetor on gasoline and diesel gensets.

Q: How often do I need to exercise my gasoline / diesel / LPG generator?

• A: Ideally, Cummins generators should run 2 hours every month. Once the genset is started, add as much load as possible (i.e., air conditioner, heat pump, hair dryers, other appliances). The objective is to place a 50 to 70 percent load on the genset.

Q: I will not be using/exercising my generator every month. What do I need to do?

• LPG — No special requirements.
• Gasoline — Depending upon your location in the country, gasoline can start to deteriorate in as little as 30 days. Treat the entire fuel tank with gasoline stabilizer. Run genset for two hours at 50 to 70 percent load. This process will circulate the treated fuel through the entire fuel system.
• Diesel — Diesel is a very stable fuel. If the recreational vehicle will be in storage greater than six months, treat the entire fuel tank with a diesel stabilizer. Run genset for two hours at 50 to 70 percent load. This process will circulate the treated fuel through the entire fuel system.

Q: How are “will-fit” generator replacement parts different from Green Label Parts™?

• A: Cummins genuine Green Label Parts are tested and designed specifically for RV applications. Will-fit parts and gaskets can be the correct shape, but because of inadequate design, the wrong material or poor quality, they could cause premature failure, leakage or performance problems. Use of some non-Cummins replacement engine parts may affect the unit’s emissions certification, and damage caused by use of oil and air filters other than Green Label Parts is not covered under your generator warranty.

Q: How often should I perform maintenance on my generator? Will doing it myself affect my warranty?

• A: The operator’s manual that accompanies each generator outlines the proper maintenance intervals and procedures for your generator. Proper maintenance is required to ensure warranty coverage remains intact. Maintenance may be performed by any engine repair establishment or individual. It is advised to keep a log of maintenance performed on your generator.

Q: What should be done to the generator oil before putting the generator in long-term storage?

• A: Before putting the RV in long-term storage, change the oil of the generator to match the anticipated temperature conditions when it will be put back in service.

Q: Should I use straight 30-weight oil, or is the multi-viscosity oil I use in my vehicle okay?

• A: Yes, it is OK to use multi-viscosity oil or 30 W for temperatures above 32 °F.

Q: Will high-octane gasoline reduce the amount of fuel varnish?

• A: No, because varnish is a form of fuel degradation that is not a function of octane level. Rather, it is a function of fuel quality, age and additive treatment. High-octane fuel without stabilizer additive will oxidize or varnish at a faster rate than fuel treated with a fuel stabilizer.

Q: When I’m checking my oil, does the dipstick need to be screwed in all the way?

• A: In order to get the correct oil level reading, the dipstick must be screwed in completely on all models with a screw-type dipstick, except for the Onan RV QG 2800/2500 model; it sits on top of the fill tube. Make sure the vehicle is level when checking oil level.

Q: How do I keep mice/rodents out of my generator during storage?

• A: Use rodent prevention techniques around the generator/compartment just as you would with any other area of your RV.

Q: Can I use my 4000 watt generator to run two air conditioners?

• A: No.

Q: Will the starter motor continue to be engaged if the start button is held too long?

• A: All Cummins generators are equipped with a start disconnect feature, which will not allow the starter to crank once the generator is producing electrical output.

Q: Why don’t I have as much power as I think I should?

• A: Your power might vary with conditions such as load and altitude. Battery chargers run as “invisible” loads, and can draw as much power as two air conditioners, depending on size. This can continue for several hours, depending on battery charger and battery bank size.

Q: Why does my generator surge at startup?

• A: Depending on the ambient conditions, the generator may surge until it reaches a stable operating temperature.

Q: Can I use synthetic oil in my generator?

• A: People use synthetic oils because the general opinion is that they can be left in the engine longer than regular oil. However, if you decide to use synthetic oil in your generator, the maintenance time intervals given in the operator manuals must still be followed.