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Randall
Randall, RVIA Certification
Category: RV
Satisfied Customers: 11926
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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This is a 2007 model Onan 4K Microquiet on my Coachhouse RV.

Customer Question

This is a 2007 model Onan 4K Microquiet on my Coachhouse RV. The genset runs fine after the vehicle has been stationary for some time but will stall out (seemingly when the AC recycles) after driving and/or stopped after driving. It is likely the vehicle sat a good while before I purchased the unit in Florida. It stalled out after about an hour to two of driving when I left the dealership. AC was replaced with a 15K Dometic and is doing the same things as with the original 13.5K unit.
JA: Did you double-check the thermostat? And what about the unit's filters?
Customer: AC unit is a roof mount/ducted unit. Thermostat seems to work although it is the original necessitating a replacement circuit board in the control box. AC works fine on shore power. I presume you mean the ac filters?
JA: Do you plan on doing the work yourself?
Customer: Depends upon the work. I am quite good with this sort of thing. My thinking is the fuel is boiling in the carb or a pressure switch is malfunctioning. I don't think this Onan has a low pressure switch. May be just a splach type oiler.
JA: Anything else we should know to help you best?
Customer: No. Don't think so. Feels to me like trash is somehow disturbed in the carb or the fuel pump/filter is not working properly.
Submitted: 2 months ago.
Category: RV
Expert:  Randall replied 2 months ago.

Hi! My name is ***** ***** I can assist you with this. I may need some additional information from you first in order to give a complete answer.

Customer: replied 2 months ago.
What info do you need?
Expert:  Randall replied 2 months ago.

The first thing would be to see if you have it overloaded. What else do you have on for any AC loads? Water heater or fridge on AC mode? Those would make a difference on hot day. The set may need some adjustment as well and a load bank test would show you that.

Expert:  Randall replied 2 months ago.

Just checking back to see if perhaps you may have missed my previous response to your question? Easy to do considering the volume of e-mail that most of us get every day! If you need me to resend this, please let me know. Thanks!

Customer: replied 2 months ago.
The genset stalls out only while driving and, yes, it is on hot days that it seems to do it. Drove the vehicle the other weekend and the ac ran fine on the genset but we turned off the ac after about an hour of driving and used the front air. My suspicion is there is either vapor locking owing to heat or the fuel pump/filter and/or carb are trashed up. The unit is 10 years old and likely sat for a number of weeks without being operated.
Expert:  Randall replied 2 months ago.

It might be or just too much load. 4K is only 4,000 watts and on a hot day the A/C can draw about 2,500 by itself. If this isn't tuned up properly or the generator isn't putting out the full 4,000 watts that can happen. Maybe have it checked and load bank tested to be sure. Thanks for getting back to me.

Expert:  Randall replied 2 months ago.

Just checking back to see if perhaps you may have missed my previous response to your question? Easy to do considering the volume of e-mail that most of us get every day! If you need me to resend this, please let me know. Thanks!