Electrical charging problems, need your interpretation.

[treejay]

Hi all, thanks for reading.

I went to inspect a '94 Chinook Concourse that I am considering buying. There were some red flags when I inspected the electrical charging system and I was hoping for input from forum members how to interpret these red flags.

There are 2 batteries in the unit. Both are under the hood. One is an Interstate "Dual purpose" RV/marine battery which I presume in the house battery. That is located under the hood, driver's side. Then there is a smaller (narrow profile) cheap looking "Automotive" battery, also under the hood, passenger side, which I presume is the starting battery.

When the engine is on, both these batteries get delivered ~14.1 volts. Seems like the alternator is working well. When the engine is cut, after a few minutes of running a few lights in the coach, BOTH batteries discharge to ~12.1 volts. This is red flag #1. Correct me if I'm wrong, but this tells me that either both these batteries are run in parallel with each other OR the idolator solenoid (I believe this is what was used in this '94) has failed in the ON position, keeping the two batteries in parallel. I don't think they should both have the same voltage all the time

Second red flag: when the unit has the generator running or is connected to shore power, both batteries have a little increase in voltage, slowly up to ~12.6. I'm under the impression that the converter should be delivering voltage at least greater than 13.0, or more. When the generator or shore power are cut, both battery voltages quickly drop back down to 12.1 or so. I interpret this that the converter is not delivering an adequate charge. Is that an incorrect interpretation?

With battery voltages at 12.1 or so with only a few interior lights on after a few minutes, maybe the furnace fan, does that indicate that these batteries are deeply discharged? The Interstate battery looks new, and they claim the "Automotive" battery is also new although to my eye it looks a little older.

Question: is under the hood where the house battery(ies) are supposed to be in a '94 Concourse? This has a 7.3L IDI diesel engine.

One more thing to add: There is evidence that a house battery existed in the hatch behind the spare tire in the rear as there are battery cables and a "footprint" left on the carpet in there. It was removed for an unclear reason, and there was no voltage being delivered to those cables, but I can't remember if we tested them with the engine running. Not sure how this is relevant to the overall picture.

Anyways, trying to interpret if this electrical charging system is faulty, which I think it is, and the primary reason I didn't purchase the rig yesterday. Let me know your thoughts or if you have any other diagnostic questions / recommendations. Cheers. Merry Christmas !

[Roly]

Treejay,

viewtopic.php?t=257

Here is an uniquely arranged 1994 Chinook manual, Concourse and Premier. I see there are options for the battery setup.

It will require some study, enjoy.

Roly

[treejay]

Thank you, I had already studied this somewhat. I did see in that manual that there are 2 options listed: "With Factory Dual Batteries" and "Without Factory RV Battery". Unfortunately, it doesn't mention where those batteries were located from the factory.

Additionally, I'm not absolutely clear how to interpret some of these schematics, in part because I don't have lots of experience with schematics and they're still a little confusing. For example I'm not sure what "Ford Pass Thru Plug" means. And on page 14, there are 2 solenoids shown. I can't tell if one is the stater solenoid and the other is the "battery isolator" solenoid. I find them generally confusing schematics.

And both those schematics have 2 batteries shown, so not sure what "factory dual batteries" refers to...

[chin_k]

Mine rig is newer, and have different setup. So take the following with a grain of salt, just like any free advice you see on the net:

1, I don't think the missing battery in the back is a standard setup. If the owner does not know about it, it is definitely a red flag.
2, anyone can kill a brand new battery in a few weeks, and some people can purposely kill it in a few days. The only thing that is worth something with a new battery is the factory warranty. If the stamped date on it is not new enough, it will be worth less or worthless when it is dead.
3, the converter in my rig should ram up the voltage quickly, so unless you are using a lot of power, you may want to assume the converter also has issue.
4, The quick voltage drop is an indication of poor battery condition.

Anyway, I think your suspicions is warranted, and you should be price the rig accordingly.