Generator problem

[janie2]

I start generator up and turn on one ac..generator rpm drops down..AC works fine for about 5 to 10 mints then you can feel fan on ac slow way down and at same time generators rpm increases back up to where it is at with no load on it..
Just spent over $300 replacing points..condensor..plug wires..spark plugs..fuel and air filters..oil and oil filter.
Also replaced both breakers on side of generator control box..
Just checked again and same issue with both ac's..They do fine plugged into house ac power supply..

 

[Gary RV_Wizard]

It could be a voltage regulator problem in the generator, but I think it more likely that the genset engine simply cannot produce the horsepower to meet the a/c electrical load. Maybe as simple as a clogged fuel filter or a failing fuel pump.
The generator speeds up again when the a/c compressor shuts off due to low voltage, thus reducing the load on the generator.

A generator is concetually simple, just an engine driving an alternator to produce 120v power. The alternator has to run at a given rpm to produce the right voltage & frequency, so the engine has to produce enough horsepower to keep it going. When the electrical load on the alternator is light, the engine has an easy job, but when a major eectrical load (lots of watts & amps), the alternator can't keep up until the engine increases its horsepower. The engine sucks more fuel & air to provide the required rpms. If it cannot increase the engine output because it is starved for fuel or air, the alternator output voltage & frequency drops and the load (the a/c) slows until it quits.

 

[Matt_C]

Janie,
I suggest that you buy a cheap (cheap in the good tool world) tool. The thing is called a Kill-A-Watt. This device can report all kinds of things. Plug it any outlet (receptacle) that the generator supplies set it to read voltage first, and watch what happens.
If the voltage and frequency stay good when the generator unloads, the what you are seeing is what the A/C unit is doing on its own.
We cam be more help if we know what is really happening.
Matt

 

[Coolhand19]

I started up generator up and turn on one ac..generator rpm drops down..AC works fine for about 5 to 10 mints then you can feel fan on ac slow way down and at same time generators rpm increases back up to where it is at with no load on it..
Just spent over $300 replacing points..condensor..plug wires..spark plugs..fuel and air filters..oil and oil filter.
Also replaced both breakers on side of generator control box..
Just checked again and same issue with both ac's..They do fine plugged into house ac power supply..

Can be a quick fix...

I have a onan 4000 in my 2022 Class C Jayco, i began to have issues with it sputtering and shutting down when turning the ACs on. I found this youtube video, and posted my comments there. Its was a simple fix, i took out about 4 oz of oil out of the onan 4000 right to the add line of the dip stick... BAM!!! Thanks goes to the guy posting the YouTube video, you'll see mine and others comments about their success as well.

 

[oldryder]

gen sounds starved for fuel or air. good advice already on checking fuel pump and filter. also check air filter. I've seen a few air filters with mouse nests in my day. Also check for damage or obstruction to exhaust pipe. My gen did the same thing after some miles of really bad road and it turned out to be a bent/kinked exhaust pipe from a rock kicked up by rear wheel.