A Quick Guide to Generator Care and Maintenance

When the generator cover has been removed, take this opportunity to give an overall visual inspection for any disconnected or loose wires as well as oil or fuel leaks. Gently clean out dirt or cobweb build up as you familiarize yourself with the normal appearance of your generator before there is a problem.

Bill and Jenn Gehr
March 1, 2013
Filed under Feature Stories

Much of the freedom we enjoy by traveling in a motorhome can be attributed to the benefits of self-containment, which is supported in large part by the onboard AC generator. Travel anywhere you wish and with the push of a button, you have full access to myriad options such as heating food in the microwave, making a hot cup of coffee, operating a hair dryer or keeping things cool inside via the use of your air conditioner. Following a few simple steps for proper care and maintenance will ensure many hours of trouble-free service from the generator.  

We’ve come to expect generator power to be available on demand, not realizing that without following regular maintenance and exercise programs, the generator may not even start. Just like the human body, if we want positive performance results, exercise is important to generator longevity. Generally, motorhome manufacturers recommend operating the generator under load at least once a month.

For exercise, run the generator with a minimum of 50 percent load capacity. For instance, if you have a 4.0 kW (4,000 watt) generator, your load will need to be approximately 2,000 watts. The use of several appliances and accessories can meet these load requirements: one or two roof air conditioners, one or two electric heater(s) or a combination of an electric heater and an electric water heater. It’s OK to run the generator for exercise at loads that vary by 10 percent in either direction. 

All generators in motorhomes are equipped with an hour meter. It’s prudent to keep a log that notes the run hours each time you check and/or change the oil level and inspect the air filter. Also include the specific hours when the generator will require service and note  any other important service intervals, i.e. repairs. It might surprise you just how quickly 500 hours can accumulate.

The hour meter

The hour meter is very important for monitoring all of your necessary scheduled services.

RV generators circuit breaker

All brands of RV generators have a circuit breaker or two that protects the sensitive electronics contained inside. Tip: If your generator is running and you are still not receiving power inside your coach, check breakers.

Onan Quiet Diesel Generator

Although the fuel filter of the Onan Quiet Diesel Generator is not easily accessible, with a little patience, it can be changed by the owner.

Onan Quiet Diesel

The Onan Quiet Diesel models provide easy access for checking oil and anti-freeze levels.

Checking the oil level

No matter what model generator is in your motorhome, checking the oil level is the single most important maintenance item.

Generac generators

Generac generators are thoughtfully designed for easy of access to all components for visual inspection, including the oil filter, as shown here.

Generator cover

When the generator cover has been removed, take this opportunity to give an overall visual inspection for any disconnected or loose wires as well as oil or fuel leaks. Gently clean out dirt or cobweb build up as you familiarize yourself with the normal appearance of your generator before there is a problem.

Onan Marquis air filter

The Onan Marquis Models air filters are easily accessible from behind the main generator cover.

Onan 4.0 kW Microquiet air filter

The air filter of the Onan 4.0 kW Microquiet is accessible by removing a single wing nut and cover.

Onan Quiet Diesel air filter

The air filter of the Onan Quiet Diesel, which requires access from underneath the generator, is still easily accessible for servicing.

 Complete an overall visual inspection every eight to 10 run hours. This may include removing a panel to gain visual access. Fuel filters should be changed every 400 to 500 hours, or every one to two years. Valves, in older-style generators requiring such maintenance, need adjustment every 800 hours. Check slip rings and brushes every 500 hours. Check the exhaust system, which includes the brackets and spark arrestor. Not all generators have spark arrestors, but those that do may require annual cleaning.

If you have a diesel generator, the water must be drained from the fuel system annually or every 100 hours of run time. The coolant, thermostat and radiator caps need to be replaced every two years on diesel models as well. Again, check the details in the owner’s manual for suggested scheduled maintenance in order to stay in compliance of specific requirements.

All models get their fuel from on-board tanks, making it important to check the rubber fuel supply lines once a year for cracks or other types of damage. Fuel leaks can be dangerous and often go undetected, especially if a leak occurs far underneath the motorhome.

Just like any vehicle, the engine oil, filter and air cleaner must be changed in accordance with the manufacturer’s suggested intervals. Consult your generator owner’s manual for the specific service details. Most gas and propane generators require oil and air filter changes every 100 to 150 hours, or once a year. Some generators do not have oil filters while others require the use of a proper type of oil filter since it may have a built-in check valve. All generators use standard automotive oil, although most manufacturers recommend synthetic oil. Viscosity and climate temperature requirements may vary from model to model; check the owner’s manual for a graph or chart that lists specific parameters and closely follow the recommendations.

Extended storage can create problems with the generator’s carburetor because the parts and passages are very small. Varnish is a result of old fuel that can collect in the jets or on the needles and will diminish their function. A few signs that the generator may be experiencing this problem are difficulty in starting, surging and abnormally high or low run speeds. Take into account that varnish can also be cumulative. Fuel stabilizers work wonders in preventing this problem when used properly. If the varnish buildup has already occurred, you will probably need to have the carburetor either rebuilt or replaced. Most motorhomes are designed so that the generator will stop running when the fuel tank is around the quarter-full mark. After the fuel treatment (STA-BIL is a good choice) is added, exercise the generator for the
recommended time and load; you will then be ready for extended storage.

Voltage and hertz are commonly overlooked maintenance considerations, yet these are critical values for proper and safe operation of 120-volt AC appliances and accessories. When linkage and carburetors begin to wear they collect dirt and dust. As a result, many of the adjustments slowly begin to change. After a few hundred hours or several years of normal use, voltage will also change. Sometimes you can detect these problems as the run speed may become a little faster or slower.

A simple meter such as  the Kill A Watt P4400 can measure voltage and hertz at a glance by way of its digital read out. If the readout on the Kill A Watt meter is outside the normal limits of your generator’s voltage or hertz, service is in order. You might want to avoid powering sensitive electronic devices until that service is completed.

Whether you’re using the generator or shorepower, being continually mindful of necessary voltage parameters is an important part of RVing. In addition, making a plan to properly care for and maintain your generator will ensure years of extended service so that the next time you push the start button, you’ll have the power to meet the electrical needs of a motorhome without the convenience of hookups. 

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4 Responses to “A Quick Guide to Generator Care and Maintenance”

  1. ben brace on March 12th, 2013 7:33 pm

    what about a generator that is fueled by propane


  2. Peter on March 23rd, 2013 4:47 pm

    Good article on generators. I have a Class A motor home with a 7.5 kva deisel generator, Oman in fact. I am always interested in getting as much Info as I can on all of the working features of my home on wheels.



  3. Nisha on September 2nd, 2016 7:45 am

    Thanks for this pretty elaborate article. We’re planning on a trip on a RV for 2 months and we were advised to bring a portable generator with is. You’re maintenance guide will really come in handy.


  4. Bruce Blais on September 19th, 2016 8:07 pm

    I have a older generator 1985 mod is there a video on oil change?


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