Onan Marquis 5000 producing only 100 volts….

[mikeylikesit]

In the middle of a long road trip and suddenly my generator won’t run the air conditioners. They work fine on shore power. Measured voltage with generator running, only getting 100 to 102 volts. The engine runs just fine, and the a/c starts and runs but won’t cool.

the manual mentions a voltage regulator….I cannot find it….is this something that can be fixed DIY, or do I need to have it serviced. I’m near Rapid City SD for the next week, but the next leg of the journey has us dry camping for a few days here and there, and I’m sure I’ll need A/C.

thanks for any advice!

 

[Henry J Fate]

Here is a thread that may help.

ONAN Marquis 5000 Low Voltage Problem

My Onan 5K has not been exercised regularly for the last several months because the engine was hard to start, running rough and stalling. Today I replaced the fuel filter and it started and ran very smooth. So, time to test.. I decided to let it run for an hour. During that hour I tried...

www.rvforum.net

My first suggestion is to varify that the generator is running properly. Rpm will change the voltage output. Rpm will also change the frequency.

Also...check the voltage at the generator outlet with a reliable multimeter. You may need to purchase a frequency meter. Frequency is directly related to rpms. 3600 rpms will produce 60hz. Check the service manual for correct specifications

 

[Gary RV_Wizard]

As Henry says, voltage & frequency depend on the genset maintaining a specific rpm, usually 3600. Low voltage or frequency is almost always an inability to maintain the necessary rpm for the load. The regulator can't regulate if the speed governor cannot get the engine to increase power to sustain the amp load.

 

[mikeylikesit]

Thanks Gary and Henry. Upon further investigation…..

1. the 30A breaker on the side of the generator control box trips immediately upon start up. If I reset it while running, it stalls the generator. The 20 amp circuit works, although it has the low voltage.

2. if I try to manually throttle the engine up more than just a tad bit, it stalls. Not sure what this means, it’s been serviced and exercised regularly. Only has about 600 hours on it.

3. it is pretty much impossible to get any mobile mechanic to come have a look at it, within the next 2 months….even though I am in a very well RV populated place like the Black hills of South Dakota. (Pretty disappointed at this) Even the larger RV shops here cannot fit me in for weeks……and I’ve got to get out of here in a week or so.

I guess I need to go to generator school so I can be self reliant, and lose my notion that if I have plenty of money to throw at it, I can get it fixed while on the road.

Plan B: go buy a small portable generator that I can use to power the shore power until I get it home. What a PITA.

thanks for the advice, guys!

 

[Lou Schneider]

Stalling when you manually advance the throttle usually points to a fuel supply problem - the engine isn't getting enough fuel to run any faster. Either a plugged fuel filter, a bad fuel pump or a partially clogged carburetor.

A quick and easy way to measure the generator voltage and frequency is to get a Kill-A-Watt power monitor, about $25-30 at most hardware stores. It's normally used to measure the power consumption of an appliance that's plugged into it, but the voltage and frequency functions are available if you just plug it into an outlet.

 

[Henry J Fate]

Start fresh with a new air cleaner and correctly gapped plugs. Replacing the oil should be on this list also but that probably is not contributing to the problem. When starting, turn off all the breakers in the service panel. The main 30 amp breaker on the 5000 should not trip. Once running check the voltage. If it is good, start turning on breakers one at a time and monitor what the generator is doing. Your air conditioning will be the biggest load so keep that in mind.

If the genset will still not throttle up, the next task would be to pull the carburetor and clean it out.

A frequency meter will give you the rpm and will also indicate any rpm variances.

Spark plugs do not do well in the older Onans. I would not expect much more than 50 hours using the Onan specified champion plugs.

 

[Gary RV_Wizard]

Stalling when you manually advance the throttle usually points to a fuel supply problem - the engine isn't getting enough fuel to run any faster. Either a plugged fuel filter, a bad fuel pump or a partially clogged carburetor.

Or clogged air filter

 

[Windybill]

the generator in my 1996 fleetwood is VERY sensitive to changes in altitude. i have to adjust the mixture screw on the bottom of the float bowl often if we are higher or lower. couple of times it would stall if i tried to use the microwave. quick and easy to try. just turned in or out until the engine is running smoothly.

 

[Rene T]

the generator in my 1996 fleetwood is VERY sensitive to changes in altitude. i have to adjust the mixture screw on the bottom of the float bowl often if we are higher or lower. couple of times it would stall if i tried to use the microwave. quick and easy to try. just turned in or out until the engine is running smoothly.

Just keep track as to where the setting is now in case you have to go back to it.

 

[mikeylikesit]

well, just to circle back and provide what I found to be the problem.....hopefully to help someone else figure out a similar problem.....

It was loose wires. On the transfer switch. Anybody know where that switch (relay) is?????

The breaker panel has a steel "divider" spot welded in......to separate the low voltage fuse panel from the high voltage wiring. The transfer switch is, unfortunately, BEHIND this steel divider. (talk about lack of serviceability!) Using a mirror and flashlight, I could clearly see the melted, burned insulation and connectors on the relay.....one of them was burned all the way thru and just bouncing around back there.
I am very thankful that the circuit breakers on the generator did their job......and prevented a potential fire.

So, drastic measures were taken. Got it home and broke out the sawzall to cut thru the spot welds, after disconnecting the low voltage circuit board and tying the wires up and out of the way. Then, had to very forcefully bend the divider out of the enclosure, to gain access to the relay. I thought I may have to replace the relay, but the contacts were all good, coil was good, so I just re-wired all of the connections on the relay. I went and bought high quality "swedge" type wire terminals, so as not to use the cheaper automotive type crimp connections. Cleaned up all the contact surfaces, used locktite on all the screws, fired it up and all was well.
I then bent the divider back in to place, and used big pop-rivets to hold it in place. Put the low voltage board back in and reconnected all the wires. Done deal, and it's been working fine since....

I'm still shaking my head at the design of the electrical panel.....how in the world would one replace the transfer switch if need be? Even changing out the entire electrical panel box would be a challenge without access to the screws on the relay........ugh!

 

[Kirk]

Some pictures would be interesting.

 

[mikeylikesit]

I was too busy inventing new curse words to take photos.....

Some pictures would be interesting.

 

[Rene T]

Thanks for getting back to us. It may help someone later on down the road.

 

[Gary RV_Wizard]

Many years ago I had a 1996 Southwind 35 which is essentially a badge-sister of your Pace. My recollection (no longer reliable ) is that the entire power panel could be pulled out. I gather that was not possible on yours? It's common on RVs that cabinetry has to be removed to gain access - they install all the wiring and plumbing before they build the interior over top of it.