Good Sam Club Open Roads Forum: High Altitude AC use causing Onan generator to die
Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Tech Issues

Open Roads Forum  >  Tech Issues

 > High Altitude AC use causing Onan generator to die

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 3  
Prev  |  Next
wa8yxm

Davison Michigan (East of Flint)

Senior Member

Joined: 07/04/2006

View Profile


Offline
Posted: 06/24/21 05:08am Link  |  Quote  |  Print  |  Notify Moderator

My ONAN had an altitude adjustment on, I think, the side of the Carb or near the carb... You may need to increase it Per page 11 of my owner's manual not all ONAN's have them.


Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times


JoeH

Apollo Beach,FL

Senior Member

Joined: 02/21/2001

View Profile



Good Sam RV Club Member

Offline
Posted: 06/24/21 05:28am Link  |  Quote  |  Print  |  Notify Moderator

wa8yxm wrote:

My ONAN had an altitude adjustment on, I think, the side of the Carb or near the carb... You may need to increase it Per page 11 of my owner's manual not all ONAN's have them.

My old Onan had an altitude adjustment lever on it too


Joe
2013 Dutch Star 4338- all electric
Toad is 2015 F-150 with bikes,kayaks and Harley aboard

garyemunson

Reno, Nevada

Senior Member

Joined: 09/27/2015

View Profile



Good Sam RV Club Member

Offline
Posted: 06/24/21 06:28am Link  |  Quote  |  Print  |  Notify Moderator

You can pry the little black limiter cap off the altitude adjuster to allow you to open the adjustment a little further. That will probably temporarily fix your issue. The jet that the altitude adjuster varies the size of is likely partially clogged. That (main jet) jet is right at the bottom of the float bowl and if any gas is left in the carb during storage, that is where the deposit builds up as it evaporates. Will cause low-power lean running that will stall the genny if a significant load is put on it. If that strategy gets it working OK again, plan on cleaning the carb jets once you are done using the RV. Onan discourages cleaning the carbs to sell new ones. Really are not too many "mechanics" capable of doing that anymore anyway. They are good, reliable carburetors that generally just have "dirty jet" issues. The main jet at the bottom of the float bowl is the most important and most often overlooked. Tricky to clean as the fuel supply enters it sideways from the altitude adjuster screw. A good overnight soak of the metal parts in lacquer thinner and "rodding out" of the passages with a broom straw (DO NOT use anything metal or you WILL be buying a new carb!!) will do the trick.

valhalla360

No paticular place.

Senior Member

Joined: 08/19/2009

View Profile



Good Sam RV Club Member


Posted: 06/24/21 07:24am Link  |  Quote  |  Print  |  Notify Moderator

Did the Onan certified tech do the adjustment correctly?

Assuming we are talking about a single air/con unit on a 4000w generator, it should be OK even at altitude. My best guess is the tech didn't do the adjustment correctly.

One simple trick you can try is to turn on the fan mode, let it settle in for a minute, then flip it over to the air/con mode. This way you don't have both the fan motor and compressor motor surging at the same time...but this only works if you are borderline. If the microwave by itself is causing it to choke, it's probably not just close.


Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV


rwynkoop

St. Louis MO

Full Member

Joined: 10/04/2005

View Profile


Offline
Posted: 06/24/21 07:46am Link  |  Quote  |  Print  |  Notify Moderator

I can second the easy start option. My 13,000 BTU AC can now be started with my 3000 watt generator when in ECO mode. In the past I had to run in normal mode.

If your generator is having problem handling the load, easy start may be the way to go. Even though it is expensive it works well.

MicroAir Easy Start - for about $330.00

Also, check this video of someone who also had a problem with their generator shutting down, even after a few ONAN techs worked on it.

Nomadic Fanatic - Fixed my generator - YouTube.

Robert Wynkoop


2003 Chevy 1500 HD Crew 4x4, 6.0L gas.
2007 Jayco 29BHS TT.

Grit dog

Black Diamond, WA

Senior Member

Joined: 05/06/2013

View Profile


Offline
Posted: 06/24/21 09:08am Link  |  Quote  |  Print  |  Notify Moderator

Look into leaning it out more. Dunno what model yo have, but some (all?) have an altitude adjustment screw.
However, it would have to be running VERY poorly, very rich to not have enough snort to at least run the microwave, even if it's a little 2500W unit.
Check spark plug. If it's fouled and or dark/black then it's running rich. Insulator ideally should be a cardboard brown color. White = lean, black = rich.

Air cleaner presumably is clean since you just had it serviced, but running no air cleaner could help diagnose, it might get a "little" more air, not significant though.

Fuel, if it's fresh shouldn't matter. Octane requirement goes down as altitude goes up. Guessing it's gasoline though since you didn't specify, but you said it's in a moho.
Possible carb plugged?


And if it's LP? I'm not familiar, but presume they have an alt adj as well?


2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29

mr_andyj

Georgia

Senior Member

Joined: 11/13/2004

View Profile



Posted: 06/24/21 09:50am Link  |  Quote  |  Print  |  Notify Moderator

4,000 watts times 0.775 is 3,100 watts at 7500 feet elevation.

RV Roof Top Air Conditioners Watts Required for start u____Average wattage once running
7000 btu RV air conditioner 1700 ________________________600
10,000 btu RV air conditioner 2000________________________700
13,500 btu RV air conditioner 2750_______________________ 1250
15,000 btu RV air conditioner 3500_______________________ 1500

from https://www.ramsond.com/wattage-chart/

So, if you have a 15,000 BTU AC then at 3100 watts you are 400 watts shy.
If you have 13.5 then you should have plenty if running ONLY the AC.
10 and 7 btu no problem. You obviously dont have these.

This chart assumes an average inefficient RV AC unit like dometic or coleman or similar.

I suspect a carb issue and that your motor, as a result, is not able to run at peak power.

My gen runs at about 42-50% capacity when AC is running (if at 7500 feet). Yours is needing most of its capacity to just keep the AC going.

* This post was edited 06/24/21 05:51pm by mr_andyj *

3 tons

NV.

Senior Member

Joined: 03/13/2009

View Profile


Offline
Posted: 06/24/21 10:47am Link  |  Quote  |  Print  |  Notify Moderator

Per the law of Occam’s Razor I would punt for a properly sized generator - per your situation, this is the right tool from your toolbox…

3 tons

TurnThePage

North ID

Senior Member

Joined: 10/08/2003

View Profile


Offline
Posted: 06/24/21 11:50am Link  |  Quote  |  Print  |  Notify Moderator

If your built in generator is genuinely running properly, I would try the following in order:
1. MicroAir Easy Start (or at least a hard start capacitor)
2. Shut off all other loads including the converter
3. Purchase a larger gen for high altitude trips (There's lots of good deals for Chinese ones out there.)


2015 Ram 1500
2004 Pioneer 18T6

SFVdave

Southern California

Senior Member

Joined: 05/18/2007

View Profile



Good Sam RV Club Member


Posted: 06/24/21 12:21pm Link  |  Quote  |  Print  |  Notify Moderator

Looking at option of removing the altitude dial which limits turning and to 5000 feet. If I can turn it a bit more may do the trick. I know it's not recommended.

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 3  
Prev  |  Next

Open Roads Forum  >  Tech Issues

 > High Altitude AC use causing Onan generator to die
Search:   Advanced Search

Search only in Tech Issues


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:




© 2022 CWI, Inc. © 2022 Good Sam Enterprises, LLC. All Rights Reserved.