My Onan 5.5 was giving me a Code 58 and shutting down about 5 min after start-up. That sensor shuts the unit down at 1200 degs I replaced the Exhaust Gas Temp but heat issue continued. I must add that this unit only has 73 hrs and my Wife had complained about excessive floor heat since the unit was new! We have an Axxess 30 ft.... it was quite a job getting to the Onan to remove the cover. I removed the muffler assembly, cut the muffler open and found a clogged Cat.....so I removed the cat converter and welded the muffler back together.......my exhaust temp went down to 214 degs at the area where the cat was and 178 degs on the exit end of the muffler. No more heat issues !!
I have an Axxess Toy Hauler 30 ft......occasionally we were getting a foul holding tank odor. I installed the Campco Cyclone Vent and all odors are now gone ! It's easy to install and was well worth the investment. The installation took maybe 30 minutes. It works exactly as advertised ! Now I'm a happy camper ! 
? Otherwise, it's going to the shop ! Thanks in advance !!
Thanks to all for the input on the small Brake battery. I'll take your advice and give it a charge when needed ! I'll post a pic when possible....I'm not very high tech. LOL !