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Old 08-08-2018, 04:01 PM   #57
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Coleman makes a 13,5K unit specifically for 2 units on a 30 amp cord. It is the Power Saver model and draws less amps. There are other 13.5K units that draw almost the same as the 15K so make sure you check the model out the shop wants to put on. The Power Saver is a couple hundred dollars more if I remember correctly.

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Old 08-08-2018, 05:46 PM   #58
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Tom.....good for you on working this out and working the suggestions of others. It was nice t see that someone understood some the technical stuff and went out and applied it.

One thing caught my attention. You replaced the dinosaur board and filled the batteries. There is a possibility your battery charger, which draws a fair amount of amperage, was coming on more frequently because of the battery condition and even the refer acting funny on A/C, stealing that much needed little extra amperage you needed to keep both A/C's running.

Don & Mary
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2016 GMC Canyon 4WD Crew Cab
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Old 08-09-2018, 03:38 PM   #59
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Originally Posted by 2008Seneca View Post
Has the generator been run regularly and when is the last time the fuel pump was changed?
or fuel filter? My quiet diesel refused to run both ACs until it was replaced.
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Old 08-09-2018, 03:52 PM   #60
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Likely overheating in those ambient conditions. There is a component on the control board that will limit current to the fuel pump when it gets hot or you could just be vaporizing the fuel in the line or carburetor bowl. Anything you can do to direct the hot air away from the cooling air inlet might help. Cummins has some air duct kits available depending on your installation.
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Old 08-09-2018, 04:08 PM   #61
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Running both my A/C units shut down my generator!

Are you referring to your coach have a 30 amp service only? Most class A coaches have 50 amp if you have two A/C roof units. =tada;4311579]I got my Bounder back from the shop today. The roof is now recoated (looks great) and two new Coleman A/C units. I previously had two 13500 BTU units, but they told me putting a 15000 BTU unit on the front would keep the main area of the coach cooler here in Tucson and in the California desert where I am taking it.

But now if I try to run both units, after about 5 minutes the Onan 5500 Marquis generator dies. I can run either A/C unit with no problem and the generator does fine. I realize that when Iím shore power, Iíll only be able to run one at a time anyway since Iím limited to 30A service.

Maybe the generator doesnít like the heat right now. Is 111į outside as I type this. Any ideas or just live with it? Thanks, Tom[/QUOTE]
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Old 08-09-2018, 05:58 PM   #62
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I looked up the Onan 5500 generator and it says:

Runs two air conditioners with power to spare (up to two 13500 Btu A/C with 2500 watt baseload)

Your 15000 BTU units may be overloading the generator. They require 7000W on startup and 3000W running.

13,500 btu RV air conditioner Start up-2750W Running-1250W
15,000 btu RV air conditioner Start up-3500W Running-1500W
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Old 08-09-2018, 07:31 PM   #63
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Iíve had that problem with a smaller generator running on a Honda 2200i. The problem is the start solenoid is too hard on the generator. When it kicks in the compressor, the 1600 watt generator is now using about 4500 watts to start. btu unit. Multiple that by 2 and add for the larger btu units p, you could be overloading the genny. If you can start them one at a time on a staggered start and they both run. The start solenoids could be the issue. You can replace them with a slower soft start solenoid... Just a thought.
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Old 08-09-2018, 09:14 PM   #64
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Converted to 50 Amp

On my Southwind I converted the land wiring to 50 Amp. When on gen I just use one AC. Otherwise you just need a bigger generator.
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Old 08-09-2018, 09:24 PM   #65
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Tom - of course this is wrong , but just think. More load is gonna be more heat, any time anywhere. The windings in the gen have a sechellac coating on them for insulating i dont know the temp they will take before melting and shorting out but. Bigger a/c = more load = more heat.
That many hours you might have some engine wear and looser fits. More load = more heat and now thinner oil maybe with looser fits you cant hold oil press and that switch is tripping you out.
My gen oil filter runs bout 250 / 270 f and oil is supposted to start breaking down at bout 300f. Running one 13,5 a/c both would trip gen out in 1/2 hour - i had weak oil temp switch tripping me out (284f) at 80f amb. . Went from 10w-30 to rotella 15w-40, thinking i should at least have better oil pressure at the higher temps amb and oil both.

Generac np66g , 5500, 300 hrs
good luck
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Old 08-09-2018, 10:25 PM   #66
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I was just talking to an Onan Tech today about this same topic as I have been having a similar issue. He asked if it was throwing fault codes which it isn't but just slowly winds down and shuts off. Second question was if it had ever backfired and yes that did happen when the carb gummed up and it ran lean. The suggestion was to then check the intake manifold for an failed seal where its pressed together. If a carbureted 5000 Marquise Gold from the early 2000's back fires it will cause the seal on the two part intake manifold to partially separate and only run on one cylinder after which it will bog down without throwing a fault. It will still be able to run 1 AC and a few other items but won't be able to hold a full load.

The manifold can be fixed however that costs more than just buying the new $78 manifold if your paying someone to do it for you. He can do it without pulling the generator but cautions that its tricky to get it out and then the new one back in place without damaging it or the seals. If you damage its seal when trying to install the new manifold then your out the $78.

The other thing to be mindful of is the 5000 Marquise Gold does require regular valve adjustments.
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Old 08-09-2018, 10:49 PM   #67
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Running both A/C units

The following is just my 2 cents and I do have a mechanics background just the same......

First - the 5500 watts the generator is rated for is probably a MAX of 5500 watts. You should NEVER exceed 80-85% of the continuous max load. Unless you want to overheat and shorten the lifespan of both the generator and the engine as well. You might want to increasing that window when temps get up and over 115.

Second - that generator was matched with the calculated load of your two original A/C units. You are well past that with the bigger unit. On hot days I suggest turning off the hot water heater and not do any laundry if you are so equipped.

I used to live in Phoenix up until a year ago July. It hit 118 and the basement A/C unit ceased. I left my job and headed north. I've never looked back on that decision!
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Old 08-10-2018, 12:21 AM   #68
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Wow. Thatís a lot more information to digest.

Iím running 15w40 Rotella in it right now.

The hot water heater and fridge are running on propane.

The generator has not back fired yet. So I hope the manifold seal is good.

Iím taking it into the shop tomorrow morning, and the owner is replacing the 15k unit with a 13.5k unit free of charge.

So with all this, and hopefully some cooler temps on the way, I may get this situation remedied.

I also spoke with Intellitec technical support. They do not recommend a 15k AC unit on a 30 amp coach period.

The lesson learned here is older coaches have their limitations. Newer 50 amp coaches can drive bigger AC units and have far better energy management systems. But they also come with higher price tags.

Thanks to all for your contributions and suggestions. I do ponder them all and do what I can with my budget and mechanical abilities to act upon them.

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Old 08-10-2018, 05:09 AM   #69
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Who was they Told you? If Rv Place was upgrading AC unit they should have told you the curent draw needed to run these units. How long is your RV? And is it not 50A service should have been if you had two(2) AC units.
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Old 08-10-2018, 07:54 AM   #70
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Originally Posted by ET-S View Post
Who was they Told you? If Rv Place was upgrading AC unit they should have told you the curent draw needed to run these units. How long is your RV? And is it not 50A service should have been if you had two(2) AC units.
I donít understand your post. I have a 36 foot 2000 Bounder that originally came with two Coleman Mach 3 ACs. The local RV place that recoated my roof and replaced the aged rear AC and dead front AC recommended replacing the front unit with a new Coleman Mach 15 and the rear unit with a new Coleman Mach 3 Plus. The local RV place said the Mach 15 only drew 3 more amps than a Mach 3 Plus. The Bounder is a 30 amp coach. But when running on its Onan 5500 Marquis generator, the generator has a separate 20 amp circuit breaker for the front AC and a separate 30 amp circuit breaker for the rear AC and the rest of the coach. Does this explain the situation to you?


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