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davejay 07-03-2019 08:27 PM

Batteries are drained
I got a problem, I'm not an electrical guy. I've been avoiding this, but I got to fix it.
Here's my problem I got 3 new batteries. When I started all my work on this thing, my batteries charged up, unplugged the coach from the house, and the fridge ran, the lights inside worked.
When we left on our maiden run, we got to Madison,wi from Milwaukee. 90 miles something happened, now, we got no power to the fridge, no interior lights, nothing. Next morning, we took it back home.nstarted fine, ran fine, but unless it's plugged into the shore power, nothing inside works. I hear a buzzing like the charger inside the coach is on, but nothing works.
Both of my coach batteries were dead. The engine battery was low, from sitting all winter. It did roll over my brand new rebuilt motor.
So I got some sort of problem with the coach batteries staying charged, or charging at all.
We're the heck do I start to look.
The isolator?
Do I got the batteries wired wrong?
Is that solenoid thing on the backside of the battery box bad?
What does it do?
I find it weird, that when running down the road, nothing works inside the coach.
Doesn't the alternator charge the batteries, and something changes that voltage over to run the internal stuff.
I'm a mechanical guy, but electrical stuff is not my forte.
Thanks. DJ

Daquenzer 07-03-2019 10:06 PM

The question is what causes the coach batteries to charge? Is there an alternator? When I had problems with car batteries not charging it was an alternator issue. Is there another alternator specifically for the coach batteries?

The other thing would be your converter is bad. I have a TT AS and I have to put the battery in use while plugged into shore power for the batteries to charge. Is there something like that? So if you are plugged into shore power do your batteries charge when you turn the switch to “in use?” If it doesn’t then it might be a sign your converter is bad.

Just a few thoughts since I’m not totally familiar with your system. Hopefully someone who has a similar set up will respond.

OTRA15 07-03-2019 10:35 PM

Hopefully one of the Classic Motorhome guys will be able to help. That sub-forum is a sub-section of this forum:

Your entire system is so much different than a trailer's, that I won't even venture a guess.

Good luck,


Smartstream 07-04-2019 01:49 AM

Look at your isolator. It is supposed to allow the alternator, center post, charge both house and chassis batteries. When the engine is not running it isolates the house and chassis batteries so if you discharge the house battery while camping the engine will still start.

You can check by connecting your voltmeter to each post of the isolator with the engine running and not plugged into shore power. The center post should read 13.5 volts or more. Each end post should read pretty much the same minus maybe .2 volts for internal loss. If this checks out measure voltage at the batteries. There are several junctions in the battery cables and ground cables to clean and check.

The relay on the back of the battery box temporarily connects the house and chassis batteries to aid in starting if needed. There is a start assist button in the glove box or on the dash that operates the relay.

Kvsterling 07-04-2019 05:43 AM

I second Smartstream, had similar symptoms on 1984 270. First bad voltage regulator in alternator. Then Found to have low fluid in FLA house batteries which would not hold charge, and isolator not completely isolating the battery banks. So it didnít charge well while driving. House battery voltages dropped rapidly once charging stopped, and battery isolator ďleakĒ then drained engine battery trying to equalize voltage to house battery. Cold weather exacerbated the problem and left me stranded. Apparently isolator are notorious for leaking charge when supposed to be disconnected. Iím considering a HD constant duty solenoid replacing battery isolator for this reason.

davejay 07-04-2019 07:22 AM

Thanks guys, I'll do some multimeter work. I was thinking it could be the isolated. Do our coaches have converters? Where would it be located. I may get a bigger amp alternates too. I suppose I could have an alt problem.
Question, if the charger inside the coach isn't wor king when plugged into to shore power, I assume then, the batteries will not charge. What made the charger stop. Blown fuse, old warn out unit, I can hear it, but where is it..
I feel like an idiot,because I can take anything apart, and put it back together, but electrical stuff just isn t my thing. So please assume I am a novice, and don't have a clue. Thanks DJ

davejay 07-04-2019 07:34 AM

What is a HD soliniod, what does do the isolator doesn't t do, and where do you buy one. Also, any custom installation nessessary?. Being an idiot in this area, I'm looking for a plug and play unit. I got to believe the isolaters of today, got to be better than the stuff from 1985. When we stopped in Madison, the next morning, it fired right up, so from a standpoint of doing what isolaters do, I think it was working. Just everything else wasn't. I thought once we got going the alternater would have run. And the batteries would start to charge, and it he inertior stuff would come back on line. No such luck. DJ

Kvsterling 07-04-2019 09:04 AM

Solenoid is essentially a mechanical battery isolator. When you apply 12v to trigger, it activates like a switch, connecting the 2 battery banks for charging both. A friend of mine has car electronics experience and reports getting a lot of customers with drained batteries, battery isolator was the culprit. In your case i would check battery and ground connections. Start at the house battery and work your way to power distribution breaker/fuses. May have a bad battery disconnect switch, bad ground, etc. I bet something has poor connect/disconnect or breaker/fuse broken. I have an stand alone Charger Iím not using, itís yours if you find current one is fried. On your floor plan, not sure where your charger/converter is located...

Waipio Rim 07-04-2019 10:19 AM

Iím no better than you with electrical stuff, but to answer your question about the charger, you should find it on the floor, curbside, under the cabinetry in the kitchen. Just follow the buzz. I replaced mine just to get rid of the buzz and because I read here that it is old tech that can overcook the batteries. I think it is also referred to as a converter.

davejay 07-05-2019 10:14 AM

Thanks guys,
It is under the sink. And it's not buzzing like normal. So I'll be looking for a blown fuse. I'll check the isolater too. All my connections are clean an tight. I did find the ground terminal on my coach batteries was loose. It was the inboard battery. So both of them could have been compromised, thus no charge. I'm thinking that is the problem. And if I blew a breaker, and the charger isn't t working, well there s the problem I think.
So, what kind of charger did you replace the loud buzzy one with. I may go that way too.
Thanks for the help guys, I don t like asking for help, but I really appreciate it. DJ

uncle_bob 07-05-2019 10:35 AM


If indeed you have the original charging gizmo from back in 1987, it is *way* past it's "use by" date. They just are not designed to last that long.

If your RV is "typical", it's been through a number of owners and had a number of "improvements" made over the years. The unfortunate result of this is that you need to do some RV archeology to figure out what's what and where. One very common add on is a battery isolation switch for cutting off the batteries in storage. Where somebody might have put it (or other bits and pieces).... who knows. Simple answer is a couple of days of poking into here and there taking notes as you go along.


Waipio Rim 07-05-2019 12:30 PM


Originally Posted by davejay (Post 2260702)
Thanks guys,
So, what kind of charger did you replace the loud buzzy one with. I may go that way too.

This is what I got from in 2011:

PM3B-60 PowerMax PM3B-60 (60 Amp 3-Stage Converter Charger)
Price: $159.00

The consensus that I have seen in other threads is to give Randy at Bestconverter a call for a recommendation, pretty sure that's what I did.

Smartstream's suggestion about the isolator is more likely to fix your problem, unless you find a blown fuse somewhere.

mayco 07-05-2019 01:10 PM

There are a number of different manufacturers of converters and a wide price range. I went with a Power Max 45 amp, 3 stage converter. It's been just fine for our needs over the last 4-5 yrs.
If you own and can read a multimeter then there are a number of different places to test what's going on with your system. All connections clean and tight to start with. While plugged into shore power you can test the output of your current converter at the converter or at the house batteries. Should be 13.5 +-. Test your isolator as previously described. If your converter is working then you may have to check for a parasitic drain on your house batteries....but, check the converter first, replacement is a wise choice at this point.

uncle_bob 07-06-2019 07:33 AM


Before you start patching things here and there, do the work to see what is and is not on the RV. Come up with a plan first. Then start buying stuff and changing this and that. Guessing at this or that is a *very* expensive way to do this.


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