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Randall, RVIA Certification
Category: RV
Satisfied Customers: 10995
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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I have a 5500w Cummins generator in my 40' RV. My generator

Customer Question

I have a 5500w Cummins generator in my 40' RV. My generator has overheated everytime i have taken it camping for two years!
This is a major head ache and im over it! Any way i can resolve tthis problem, my family wantsme to return my RV!!
Thanks, Ken
Submitted: 1 year ago.
Category: RV
Expert:  Randall replied 1 year ago.

Good morning, Ken..........and thanks for bringing your question to us here at Just Answer! You need to get to the bottom of why it is overheating. This usually has to do with air flow or oil levels, but it might be due to an incorrect setting on the air/fuel mixture on the carb which is allowing it to run too lean. Is this a gas powered set or LP set? Are you sure you are checking the oil properly? If the oil level gets too low it will overheat and shut down. Hope this proves helpful here. Please get back to me if you need more as all follow ups are included in our fee.

Customer: replied 1 year ago.
I have been checking the oil level. How do i check the air flow on the carberator. What should i try ? Gas level ok.
Customer: replied 1 year ago.
Its a gas powered
Expert:  Randall replied 1 year ago.

The air flow that is for cooling is around the motor and out the vent. Check for any obstructions like insulation that may have moved. Do you check the oil level by setting the dipstick in the hole or screwing it in? If there is some debris in the carb jet it may cause it to run lean and hot. Be sure that the spark plug is correct. The wrong plug can do this. Do you have an RV shop locally that can do some of this for you?

Expert:  Randall replied 1 year ago.

What brand of oil and weight are you using?

Customer: replied 1 year ago.
This is a pretty new RV. I have taken it in to RV World where i bought it and they say they have run it for several hours and it doesnt overheat for them (BUT IT DOES FOR ME), There doesnt seem to be any insulation obstructions and i check oil by screwing dip stickin all the way... The dealer changed the oil sothey should have used the correct weight oil (not sure what they used). Havent had them check blockage for fuel to carberator. I guess icould get them to check that if i complain enough.. By the way. Yes the RVis still under warranty. I take it in and complain and i get still an overheated generator,,,,!,,!
Customer: replied 1 year ago.
Should I be using a certain weight oil?
Expert:  Randall replied 1 year ago.

Check the oil with it just sitting in the hole..........NOT screwed in. I would use Chevron Delo if you aren't using the Onan oil. It is pretty important both the weight and brand. Check your manual for the recommendations based on ambient temps where you are running it. Many RV shops really don't have good techs for Onan units. I would invest in a good shop manual for this set so you can check some of this yourself. How much of a load do you have on this when it overheats?

Customer: replied 1 year ago.
Since it has been changed at the dealer I hope they are using the right brand name and weight. What weight?
Some times the AC is on in the summer I turn it off but leave the generator on to keep the frig , etc running.
Customer: replied 1 year ago.
It still overheats
Customer: replied 1 year ago.
Hello. ?? Really... invest in a shop manual..??? Thanks for the help. Lets see... did i get any solutions that i havent already tried... no!!!!
Expert:  Randall replied 1 year ago.

Sorry for the delay in getting back to you..............someone changed the category and I couldn't respond! I was trying to get you to see that having manuals for your systems is always a good idea if you want to do your own repairs and diagnosis. I can only do so much from here. If this is still under warranty, you might want to get it done at a shop that specializes in Onan repairs and not just you RV dealer. It may be a defective set. These are made in China now and not near the quality of the ones from years ago. The manual would give you all the basic information you need to properly maintain this yourself so far as changing filters, oil and minor adjustments. If you feel it wasn't helpful then you can always ask for a refund as we guarantee 100% satisfaction here.

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