1986 itascia engine battery/12volt dc batteries

[dowis]

1986 itascia motorhome i just picked up at the end of fall last year. question why would the 12v dc batteries be starting the engine and not the engine battery. if this is the case, i could not go off gridding due to using the refrig on gas and the lights if the 12volt dc batteries are starting the engine.

[Jim_HiTek]

Could be a previous owners modification, could be a factory wiring choice, could be miswired. The way it came from the factory would be 2X 6 Volt Deep Cycle batteries for the house, and 2X 12 Volt starting batteries. Or just one starting battery.

Typically, a class A of that era would have a battery or set dedicated to starting the engine, then another set of 6 volt batts wired in series to provide 12 volt for the house 12 volt equipment along with the lighting. That's because a 6 volt battery is a Deep Cycle battery but few 12 volt batts are...despite what the ad at WM might say. A starting battery is set up for cold cranking amps over a short period. A 12 volt deep cycle would be twice as tall as they usually come. Some owners opt for the less expensive 12 volt batts when their 6 volt deep cycle batts need to be replaced but that's a fools choice. Especially if you plan to dry camp.

Then, the charging systems of older RVs like that (and even some new RVs) neglect to provide charging for the chassis batteries except when the engine is running. So after 5 days of dry camping, they have died. Many owners add/added the Trik-L-Start or Amp-L-Start devices to suck juice from the house batts to keep the chassis batts topped off. But of course that means there needs to be some way to charge the house batts. Like staying at an RV park with shore power.

Which may be solar...some RVs of that age came with an optional roof mounted solar panel that was worthless (only 8-10 Watts) and some owners beefed that up with a 100 Watt panel, usually that charges the house, not the chassis batteries. But with a Trik-L-Start or similar (and there are other devices for this job) then that solar can be shared. Some solar systems are set up to also charge the chassis batts. If you want to dry camp for days or weeks...you'll want to have at least 400 Watts of solar.

[dowis]

I am trying to find a wiring stamatic but having no luck in finding one.

[Jim_HiTek]

You need to contact the chassis manufacturer for some of that, and the house manufacturer for the rest. It's complicated.

Get the VIN from in front of the driver on the dash, or on the placard next to the driver, and enter it into Google for lots of chassis info. Then try to contact the manufacturers. Many of them have archives of old schematics for their equipment. Even after having been sold many times over.

You might check the basement power area. See if there's a large BCC (Battery Control Center) in there as that will have a name and model number printed on it's cover so you can google that. Or the schematic for it will be printed on the back of that cover.

In my '94 Bounder it was a 12" X 9" covered box with all the electronics needed to control the battery charging including that which came from the solar panel and other fun stuff that's fed to the house. Right next to that were several large automotive solenoids that did the switching. My RV had two momentary push switches just above the entrance door to also control solenoids there. Called the saleman's switches back in the day. Those disconnect the batteries from most but not all of the 12 volt loads.

[Morich]

I might throw in some info that I find looking at the 1990 model as Winnebago does keep things for a long time if they find they work!

I suspect there is some confusion on which batteries are doing what as I see this drawing looks very much like the models going clear up to around 2010 or after.
Looking at this diagram of a 1990 model which is as old as online goes:
https://www.winnebago.com/Files/File...990/089949.pdf

Top center of first sheet shows the mode solenoid and at right top is the way the batteries were built. I see the normal two 12 volt batteries used for coach things and one 12 volt used for starting. On this RV the second coach battery was an option!
Two on left are 12 volt wired in parallel with one on right used for chassis/ starting. Each set has a cable to the solenoid with a control wire LR used to operate the solenoid to connect two groups together. This is the way many, many Winnebago were built for decades!

Click this drawing of the 1990 model to get a better view or go direct to get the bigger story?



My first point to question would be what makes you think the coach batteries are starting the engine? Not saying you are wrong as I'm not where I can see near as well as you but it should not be that way, so first we need to get what is actually happening cleared up.

Being aware that folks change things over the year, it looks like this second coach battery was an option when new, so it is quite possible, somebody changed out one 12 volt that came without the second battery option and added two 6 volt in place of their one 12 volt? Not the best use of space if yu have space for two 12 volt but then there are reasons for folks doing strange things at times.
But then take a look to see if this matches any of what you have and we can sort it better.