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Old 07-27-2015, 05:42 PM   #57
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Originally Posted by bkahler View Post
Dean, aside from the inverter and solar is the wiring still factory?

The reason I ask is the DC converter appears to be feeding the DC buss through a 30 amp circuit breaker. All the wiring diagrams I've seen for these coaches shows a fuse (usually 50 amp) instead of a breaker along with a fuse on the negative feed as well.
The converter, 12v fuse panel and 30amp circuit breakers are not original.

Yes, when on shore power, the 12v main bus A is feed via the 30amp circuit breaker. The coach 12v systems are fed off the 12v fuse panel as you know and when on shore power (inverter), the coach batteries are "back fed" to charge them. As well as the firewall bus B is being fed (12v outlets on dash board and dash board stereo system.

The original 12v fuse panel with its two large fuses like you described went up in smoke one late evening about 5 years back. That's when I installed the new components and the circuit breakers.

I'm using the circuit breakers instead of the fuses. Most of the modern wiring that I have seen doesn't have a fuse on the negative side. Fusing/Circuit breakering the firewall bus B is also new...it used to be feed off the main coach disconnect with no fusing.

The main disconnect is located on the stair well and the batteries (all) are located right behind the step well. The circuit breakers are located right in this area as well as to keep them as close to the battery + terminal as possible. All are withing 1-2 feet of each other (except for the 12v fuse panel and converter which are under the bed).
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Old 07-27-2015, 05:46 PM   #58
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I would like to replace the chassis battery "knife" shutoff switch with the same type of main disconnect that the coach batteries use. If there was ever an electrical fire on the engine side, I would have to lift up the battery hatch and rich down between the batteries to get the the knife switch and I'm afraid that just might be where the electrical fire might start!
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Old 07-27-2015, 05:55 PM   #59
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Originally Posted by bkahler View Post
I'm pretty sure this problem never occurred on the my old 310. Probably just got lucky in that regard

My guess is the diesel 310 and the 454 310 probably have similar DC wiring with the exception of the battery tie-in for starting. I can always compare notes between yours and my old 310 (currently stored at my place).

What I'm not sure I understand yet is why your chassis battery is not being charged by the DC converter (aka Univolt) with the disconnect switch closed yet the coach batteries are (or are they?). If the chassis and coach batteries are tied together when the disconnect is closed then the chassis battery should be getting a charge from the converter. You can test this theory by taking voltage readings of each battery with the disconnect switch open. If the chassis and coach batteries read the same voltage then they are probably connected together somewhere. If they are not reading the same (i.e. within .2 volts or so) then they are not tied together. Now do the same thing with the disconnect closed. Are the readings the same or different?

I know you've verified the diode isolator wiring but for some reason I keep thinking back to that device due to the fact that it has a diode in it. Lets leave that on the back burner for now and do some more testing.

As onerous as this may sound the best way to isolate a problem like this is to literally disconnect all electrical devices from the batteries. Disconnect via pulling fuses, disconnecting wires from terminals and any other method required to isolate each individual circuit from having power.

Once you have every known circuit isolated then monitor the batteries with the disconnect switch closed. If the coach battery still drains then you haven't isolated everything. If it stops draining you have at least proven that one of the circuits is the culprit.

A side benefit of this sort of testing is you can map out your wiring and have a nice handy reference chart that will help in diagnosing problems down the road.

Hope this helps!

Brad
If indeed the two systems are mistakenly tied together I also dont understand why the converter wouldn't be charging the chassis battery also. I dont have a clear understanding of this entire ignition/charging system. When I replaced the battery isolator under the hood, I referred to the Airstream manual to insure that the new isolator was installed the same as the original (or what was there).

The chassis battery seems to hold a good charge (12.4-12.5) when I use the disconnect but I havent taken the battery out to have it tested. It was under 10.0 the last time I had forgotten to use the disconnect but after a couple hours on the road it had charged back to about 12.43 and thats where it is at aprx right now. The alternator is putting out between 14.7 and over 15 depending on rpm.

A couple of days ago I turned on both my exhaust fans in the afternoon, chassis battery at 12.43 , and let them run till early the next morning. Plugged into shore power. Tested voltage and the chassis battery was down to under 10 volts. Coach batteries stayed charged, coverter doing its job. The only thing that I could come up with is that those exhaust fans had drained my chassis battery down, nothing else on over night. So thus my thinking that somewhere the two systems are tied together somewhere and the coach batteries are reveiving a charge from the converter and the chassis battery is not, duh! You would think it would if indeed they are somehow commingling.

So, converter is working, alternator is working, looks like the battery combining solenoid is working, but the battery isolator? Even though I removed and replaced as the old one was, same type isolator but a little higher amp, dunno. At first glance at the wiring for the isolator I thought the alt post and battery #1 post should be reversed but I installed according to the manual and the one that was removed. Ill post pics of the isolator wiring/ old and new.
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Old 07-27-2015, 06:06 PM   #60
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Old isolator
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New isolator
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Center terminal on both is alternator, left terminal coach batteries, right terminal "to engine battery through Chevrolet harness" (quote from manual) at a glance, I thought the wire on the right terminal and the wire on the center terminal should be flip flopped but as you can see from the pictures I installed as per the old isolator.


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Old 07-27-2015, 06:13 PM   #61
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10 volts on a battery probably means it is dead. You should probably pull it and have it tested.

The 12volt Side of Life (Part 1)
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Old 07-27-2015, 06:15 PM   #62
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Dean, indeed the way my system is supposed to be working, as far as charging is concerned is the converter charges coach batteries only and the alternator will charge both the coach and the chassis batteries through the isolator. It was my understanding that the isolator will detect which needs the charge and both controlled through the internal voltage regulator. I have 12v coach batteries. Thanks for your input Dean, really nice schematic youve produced there.

Mike
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Old 07-27-2015, 06:18 PM   #63
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Well I was wondering about that, Ill pull and have it tested tomorrow. This has happened now more than once so I guess there is a good possibility Ive murdered the defenseless thing. (Its only a year old)
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Old 07-27-2015, 07:11 PM   #64
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Dean, indeed the way my system is supposed to be working, as far as charging is concerned is the converter charges coach batteries only and the alternator will charge both the coach and the chassis batteries through the isolator. It was my understanding that the isolator will detect which needs the charge and both controlled through the internal voltage regulator. I have 12v coach batteries. Thanks for your input Dean, really nice schematic youve produced there.

Mike
My isolator/alternator combination uses a "Sense" wire off the alternator to tell the regulator built into the alternator whether to charge or not. This additional wire coming off the alternator is connected to one of the battery connections on the isolator.

Originally this wire was connected to the post for the chassis/engine battery. My coach batteries never seemed to get charged up when driving. I connected this sense wire to the coach post on the isolator. I figure that the chassis battery won't get run down much when on the road and dry camping but the coach batteries will. So I want the alternator to "sense" the charge needed on the coach batteries and keep outputting and charging until the coach batteries are charged up.

The forth small terminal on my isolator is coming from the ignition switch which is required to "excite" the isolator/alternator ? I think this is typical on the early GM gas engine setups (CS and CI alternators).

My dad had replaced the alternator a few times as evident by the shop receipts I have. It was dead again when I wanted to get the rig road worthy again. So I figured there was something wrong.

I replaced the alternator with a very expensive 200amp high output unit and installed the large 240amp isolator (with large fuse and large cable from alternator to isolator). I had to move the new windshield washer tank/pump to the other side of the firewall. My expensive alternator burned out quickly on the first trip to Burning Man.

I'm not sure what actually solved the problem, but all is working now and has been for a while. Here is what I did...

I replaced several wires from the isolator to the alternator and on the extra solenoid that is installed to prevent hard or inadvertent starting on the 454. I ran a new wire from the chassis post of the isolator to the engine battery. I also one day got under the chassis and removed the starter heat shield to look at the wiring connections. It was a fire waiting to happen. I put new connectors on all the wires to the starter and cleaned off as much oil as I could.

I replaced the burned out expensive 200amp high output alternator with a stock but rebuilt 130? amp alternator by a local starter/alternator shop. I learned my lesson once again on the "high performance" parts that make no difference on a motorhome!
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Old 07-27-2015, 08:09 PM   #65
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If indeed the two systems are mistakenly tied together I also dont understand why the converter wouldn't be charging the chassis battery also. I dont have a clear understanding of this entire ignition/charging system. When I replaced the battery isolator under the hood, I referred to the Airstream manual to insure that the new isolator was installed the same as the original (or what was there).

The chassis battery seems to hold a good charge (12.4-12.5) when I use the disconnect but I havent taken the battery out to have it tested. It was under 10.0 the last time I had forgotten to use the disconnect but after a couple hours on the road it had charged back to about 12.43 and thats where it is at aprx right now. The alternator is putting out between 14.7 and over 15 depending on rpm.

A couple of days ago I turned on both my exhaust fans in the afternoon, chassis battery at 12.43 , and let them run till early the next morning. Plugged into shore power. Tested voltage and the chassis battery was down to under 10 volts. Coach batteries stayed charged, coverter doing its job. The only thing that I could come up with is that those exhaust fans had drained my chassis battery down, nothing else on over night. So thus my thinking that somewhere the two systems are tied together somewhere and the coach batteries are reveiving a charge from the converter and the chassis battery is not, duh! You would think it would if indeed they are somehow commingling.

So, converter is working, alternator is working, looks like the battery combining solenoid is working, but the battery isolator? Even though I removed and replaced as the old one was, same type isolator but a little higher amp, dunno. At first glance at the wiring for the isolator I thought the alt post and battery #1 post should be reversed but I installed according to the manual and the one that was removed. Ill post pics of the isolator wiring/ old and new.

This may sound sort of off the wall but I'm wondering if your coach batteries are actually tied into the coach DC buss. I say that because your chassis battery acts just as I would expect after having powered two fans for as long as you indicated with out being charged at the same time.

Do this, disconnect the chassis batteries so that you know they are not jn the system. Now try the different positions of your disconnect switch and see what happens.

At some point I would repeat the above with your DC converter unplugged. The idea here is to see what does and doesn't work on the chassis battery.

There just has to be something obvious that we're just not seeing yet.
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Old 07-27-2015, 08:21 PM   #66
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This may sound sort of off the wall but I'm wondering if your coach batteries are actually tied into the coach DC buss. I say that because your chassis battery acts just as I would expect after having powered two fans for as long as you indicated with out being charged at the same time.

Do this, disconnect the chassis batteries so that you know they are not jn the system. Now try the different positions of your disconnect switch and see what happens.

At some point I would repeat the above with your DC converter unplugged. The idea here is to see what does and doesn't work on the chassis battery.

There just has to be something obvious that we're just not seeing yet.
Brad, did you mean "disconnect the chassis batteries" or the "coach" batteries?
Take the coach batteries out of the equation to see if anything still works with just the chassis battery connected?
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Old 07-27-2015, 08:22 PM   #67
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Well I was wondering about that, Ill pull and have it tested tomorrow. This has happened now more than once so I guess there is a good possibility Ive murdered the defenseless thing. (Its only a year old)
Yeah definitely have it tested. The good news is I've had batteries discharged that far and they recovered. Good quality batteries have a better chance of surviving.
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Old 07-27-2015, 08:27 PM   #68
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Brad, did you mean "disconnect the chassis batteries" or the "coach" batteries?
Take the coach batteries out of the equation to see if anything still works with just the chassis battery connected?
Sorry, I meant the coach batteries. The thought is to see what circuits work with the chassis battery especially when the disconnect is ppen.
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Old 07-27-2015, 08:33 PM   #69
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I'm certainly not an electrical guy but after reading the above especially Brad's last post why not disconnect the coach batteries and start turning things on to see if anything is connected to the chassis battery that shouldn't be? Kind of what Brad said but maybe a more direct route.

Sorry, I guess Brad beat me to it while I was typing.
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Old 07-27-2015, 08:38 PM   #70
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Ok, thats what I thought you meant. Good idea.

Dean, Ive got the 3 post isolator. Im not exactly sure where the second wire on the battery "1" terminal and the battery "2" terminal go. I was assuming one goes up to the voltage gauge in the dash "1" terminal, and the one from the "2" terminal is a sensing wire. But Im not sure on either.........Ive obviously got some testing to do here.........thought this might be an easy one but like everything else on these rigs, budget 2 hrs and it will take 10.
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