# Why Will My 4000W Champion Generator Not Run My Roof Air Conditioner?



## WERA976

My generator must be getting weak!?! It's a Champion 4000W (4000W surge rated, 3,750W service rated). But I don't know to be sure if this is a problem with my A/C unit, or a problem with the generator running the A/C unit.

The generator will run low-power stuff like lights and fans easily, but starts to grumble when the power requirements increase. When we were testing it, it really stumbles and stuttered when we tested it with a vaccum cleaner, and will not run my 13.5K BTU roof A/C on the RV at all (through the 30A 3-prong RV plug).

The generator loses revs, shakes & stumbles and sounds awful when the big stuff is connected. The needle goes below 100V then smoothes out and returns to 115V when the vaccum was switched on, but later when tested it with the A/C, when the compressor cycles, the needle on the generator dives under 100V, stays below 100, and the motor never recovers.

How do I go about tracking down this problem? Is there a typical "thing" watch out for?

Should I start with the generator - I think I've eliminated any problems with the engine side (the carb's clean, it starts easy, the gas is fresh, etc.), but maybe the power generating side is not producing adequate power? Or might it be more complicated?

Or is the A/C unit the more likely culprit - Is there something I should know about the roof A/C on this new Outback that's more complicated than the other three roof A/Cs I've run on previous TTs? Should I add a capacitor to the A/C to help the soft starting issue? I am completely lost.


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## wolverine

I have a similar generator that has a 3500 surge and 3000 continous output. I tested my generator on my AC when I was dry camping this spring and my voltage dropped to 110 when the AC started and then the voltage stayed at 117 volts. My generator is a Honda clone that I bought at Pep Boys. I just used it to power my house during a power outtage we had last weekend that lasted 72 hours. It ran 2 refrigerators and 1 freezer plus my house lights, but not my well.


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## CamperAndy

Sounds like a dirty carb. How old is it or better yet how many hours does it have and how often do you run it at load?


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## 2500Ram

Ok my gen is very similar 3500w Champion. here is what I had to do to get mine to finally run up here at altitude.

I made sure there were NO loads on the gen, 12vcharger water heater everything shut off at the breakers but the main and AC. Start up the gen, let it run for a few minutes and then start the AC. I can not run anything else when the AC is on or it bogs it down horribly.

let me suggest this little gem to get your gen's output as close to 120vac and 60hz









clicky thing for $20 and free shipping

I had to play with the RPM's on the gen after a few years to get it to power my AC again, I can only guess the idle adjustment backed out some with the vibration over time.

Good luck.


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## maddog

2500Ram said:


> Ok my gen is very similar 3500w Champion. here is what I had to do to get mine to finally run up here at altitude.
> 
> I made sure there were NO loads on the gen, 12vcharger water heater everything shut off at the breakers but the main and AC. Start up the gen, let it run for a few minutes and then start the AC. I can not run anything else when the AC is on or it bogs it down horribly.
> 
> let me suggest this little gem to get your gen's output as close to 120vac and 60hz
> 
> 
> 
> 
> 
> 
> 
> 
> 
> clicky thing for $20 and free shipping
> 
> I had to play with the RPM's on the gen after a few years to get it to power my AC again, I can only guess the idle adjustment backed out some with the vibration over time.
> 
> Good luck.


X2 I had to adjust the rpm on my 3500/3000 Champion. It needs to run a high enough rpm to maintain a 60hz.


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## Dan Borer

I have the same generator and it runs all my stuff just fine. I also have the 1200 watt unit and had similar problems with it not carrying a load. A call to Champion got a tech to talk me through a couple of tests to determine the cause of my problem. A couple of days later a little box showed up at the front door with an little black electronic thing in it that made it work as advertised after replaceing the defective one on my generator. Here is their website: http://www.cpeauto.com/faq.php .

Good luck!

Dan


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## Just Add Dirt

I have the exact same generator and it run everything just fine on my 28KRS including the A/C and the Microwave at the same time! You either have a dirty carb or bad gas...is my guess; try fresh fuel with a little STP carb cleaner in it. 
Eric


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## Juan

I have a 2009 Champion 3500/4000 that I bought last year. I just ran it today while loading my trailer. It ran the A/C and the fridge no problem at my house which is at about 6000ft. I'll check to see if it runs my A/C tomorrow at 8500ft. Must be a generator issue. Maybe due for a good tune up??? If I remember correctly, my gen came with a extra set of brushes or something like that.....maybe something to think about?


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## jstew03

I have a similar (or perhaps the same?) generator - 3500 Run / 4000 Peak. I find that it doesn't like running the AC and refridgerator at the same time. If I put the fridge on gas (vs auto) it works.


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## letscamp

I'd try running some of the STP with fresh 91 gas through it. My older gen did not want to start up the a/c either on the first few attempts, but I read somewhere on here on another topic to start the fan for the a/c first for a good 30 sec. Once you hear the gen level out turn the a/c to on. After I did that it seemed to work just fine every time. I'd stick to running the fridge on propane for a few min before running that with the gen too.

I don't know if or what people think around here about running the gen with 91 octane, but my generator runs a lot stronger and smoother, you can give that a shot. Good luck, camping in 100+ with no a/c = no fun


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## Tangooutback

The best thing to do is to install a hard start capacitor kit on your a/c. The issue is surge current at start up, which is usually 18 to 22 amps, for about 20 to 40 seconds. Once the compressor stabilizes it draws a mere 10 to 12 amps. I just double check specification and at stabilized state, compressor draws 12.8 amps.

Without a hard start capacitor your compressor tends to expire prematurely due to inadequate current supply everytime the compressor kicks on.

http://www.arnoldservice.com/compressor_hard_start_boosters.htm

Get the Supco SPP6E Super Compressor Boost Hard Start Capacitor, price $30.
You can install this hard start capacitor yourself or hire a tech to do it for you.

If you want to do it yourself, visit this site for instruction

http://2manytoyz.com/air.html

If you think your generator is having issue with dirty carburetor and therefore its RPM is not up to snuff, buy a can of SeaFoam from Walmart and add it to the fuel tank. Double up the prescribed dosage. I use it on my diesel truck and boat to clean out fuel injectors. 
If SeaFoam does not fix the problem, then the problem is either in something else other than the carburetor OR your carburetor has gummed up so bad. In this case the only fix is to take the carburetor out and mechanically clean it with compressed air and piano wire.....OR...if you have an ultrasonic cleaner it would do a nice job for you.


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## WERA976

Sorry I haven't responded, since last Thursday night we were at the racetrack. Man, it was hot! We were able to have shore power at the track, so my generator problems weren't so dire, but they will be an issue here, shortly, as we'll need the genny in about 2-3 weeks when we do some dry camping.

Some updates: I've gone through the carburetor, and it's clean. I found no evidence of any gum or varnish. So it's not a carb problem. It was stored with Sta-bil, anyway, and even then I drained that out and filled the tank with about 1/2-gallon of fresh 93-octane w/ Gumout carb cleaner mixed in it. I put the carb back together and ran the generator for about 30 minutes w/ no load, and it ran fine. It started 2nd pull on the choke, and when I move the governor lever by hand the revs rise & fall accordingly.

I believe it's a power plant issue with the generator. The building inspector here at work is bringing in his Fluke tomorrow, and we're going to do some diagnostic tests (no joke - I'm bringing in a desk fan, drop light, microwave, and vaccum) to see how much it's putting out.

I asked him about the capacitor issue - he says RVs are probably wired w/ 16-ga wire, not up to the task of carry the added load of the capacitor and would likely burn to the ground if I added one. Does anyone know the wire size of the power lines going into the roof A/C unit?

I like the idea of calling Champion and seeing if they can help me. After tomorrow's test, when I have some diagnostic numbers written down, I'll call them and tell them what's going on and when. Maybe they can lead me in the right direction.


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## GarethsDad

By building code a 15 amp circuit must use 14 gauge wire. A 20 amp circuit will use 12 gauge wire and the 30 amp main uses 10 gauge wire. The 12v dc side uses 16 gauge wire. James


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## CamperAndy

WERA976 said:


> I asked him about the capacitor issue - he says RVs are probably wired w/ 16-ga wire, not up to the task of carry the added load of the capacitor and would likely burn to the ground if I added one. Does anyone know the wire size of the power lines going into the roof A/C unit?


Lots of people use larger capacitors to help start the AC unit. That is the reason for the cap to help with the initial in rush, there is no fear of damaging the wiring. It does not matter what the supply wire size is but it is #14 which is to code for a 15 amp circuit.


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## WERA976

I climbed up there last night and took some pictures of the unit. It's a Coleman Mach (Mach III I assume???) A/C unit. The wires I saw were labeled for 105*C and were either 16 or 18 AWG.

I fired up the generator this evening and took some readings with a multi-meter. With no load it's producing between 13.89 - 14.20 amps. I ran a hair dryer, no drama. I ran the vacuum, it stumbled and then slowly recovered. It would not run both the vacuum and the hair dryer simultaneously.

The hair dryer had no appreciable effect on amps, they stayed about 12-13 when it was on. The vacuum would pull the amperage down to about low-11s or middle-10s. Both together would read mid- to high-8s and the generator would shake like a paint mixer and the engine was bogging to keep itself running.

I'm calling Champion tomorrow to see what I can do now.

I'm also installing the soft start capacitor in the A/C unit to protect the generator for the future.


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## WERA976

Just Add Dirt said:


> I have the exact same generator and it run everything just fine on my 28KRS including the A/C and the Microwave at the same time! You either have a dirty carb or bad gas...is my guess; try fresh fuel with a little STP carb cleaner in it.
> Eric


Sykesville, huh? I grew up on the Ho. Co. side of Woodbine. Graduated from Glenelg in the 90s.


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## Traveling Tek

What ever happened here? I just bought on of these Gennys and would like to know how to keep it running great.


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## KTMRacer

WERA976 said:


> I climbed up there last night and took some pictures of the unit. It's a Coleman Mach (Mach III I assume???) A/C unit. The wires I saw were labeled for 105*C and were either 16 or 18 AWG.
> 
> I fired up the generator this evening and took some readings with a multi-meter. With no load it's producing between 13.89 - 14.20 amps. I ran a hair dryer, no drama. I ran the vacuum, it stumbled and then slowly recovered. It would not run both the vacuum and the hair dryer simultaneously.
> 
> The hair dryer had no appreciable effect on amps, they stayed about 12-13 when it was on. The vacuum would pull the amperage down to about low-11s or middle-10s. Both together would read mid- to high-8s and the generator would shake like a paint mixer and the engine was bogging to keep itself running.
> 
> I'm calling Champion tomorrow to see what I can do now.
> 
> I'm also installing the soft start capacitor in the A/C unit to protect the generator for the future.


your measuremments contradict your text. With no load, there is ZERO amps by definition. Also, when you plug in the hair dryer amps should go way up, typical hair dryers will draw 10-12 amps on high heat. Plugging in the vaccum should have increase the amps by 6-10. Sure your not measuring voltage? (140V no load, 110 with hair dryer, 80-90V with both) Don't know how clean a sine wave the champions put out, but if it's not clean, most voltmeters(any non true RMS) will not read voltage correctly. they are calibrated assuming a pure sine wave on AC. A 3KVA unit should run both a vaccum and hair dryer, but just barely, total draw could be near 3KVA.


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