Alternator Problem

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Alternator Problem

December 23, 2018, 11:14:43 pm

Greetings,
We just took possession of a 1991 GV yesterday, and I'm hoping to get some help figuring out a problem with the alternator. The PO replaced the old alternator with a Leece Neville 160Amp (I don't know what the old alternator was) and the battery isolator because he wasn't getting a charge to the chassis battery. No success. He had the new alternator checked, and it works, but still no charge getting to the batteries.

I've read a number of threads talking about remote exciters and battery sensors, but I'm not an electrician, so my knowledge is limited. It seems the PO knew less because he didn't know anything about either. He claims the shop that sold him the new alternator says it doesn't require the exciter, but said nothing about the battery sensing wire. My guess is that the missing battery sensing wire is the culprit, and here's why: There is one smaller gauge wire in the loom from the alternator to the isolator that the PO didn't hook it up because he didn't know where it went. I agree, as you can see by the picture, that it isn't clear. The alternator has 3 studs available, but no markings as to what they are for other than "AC" under the middle stud.

Here's where things get exciting. I hooked one lead to the "battery 1" terminal on the isolator (which goes to the chassis battery) and with the engine running touched the other end to one of the alternator studs (the right one I believe). There was a pretty good spark, the rpms lowered a bit like happens under load, and my friend monitoring the volt meter noticed the voltage at the chassis battery increased to 13-something volts. Success? My question is whether the big spark is normal (it heated the wire a bit, but not enough to melt it). I only left the connection in place for about 5 seconds before removing it, after which the rpms increased again to normal and the voltage at the battery dropped back down to 12-something. Before I go hooking things up permanently, I'd like to hear what someone with more experience has to say.

Re: Alternator Problem

Reply #1 – December 23, 2018, 11:29:33 pm

Welcome to the ForeForum.

I would NOT guess as to what terminal the sense wire should be attached to-- may be a quick way to "let the smoke out".

Should be easy to go on-line and get a wiring diagram for your alternator showing exactly which terminal on the alternator is the "sense terminal".

Re: Alternator Problem

Reply #2 – December 23, 2018, 11:33:57 pm

I recommend you DO NOT try touching the little wire between the big studs again. What you were doing was connecting the POS output post on the alternator to the POS start battery terminal on the isolator. The little wire got "warm" because the alternator was trying to charge the start batteries through the little wire. Do that for more than a few seconds, and you will definitely let the smoke out.

Here is the factory sheet on your alternator:

Prestolite - Leece Neville

Read the 3rd line from the bottom. You'll see this alternator does not have remote sense function (in stock configuration). The 3 small terminals have nothing to do with "remote sense" or "excitation". This alternator is not correct for installation with a diode based battery isolator. It may be possible to modify the alternator to work with a remote sense wire, but this would require locating a competent alternator shop where the techs understand how your dual battery + diode isolator setup works.

As a temporary fix, you could move the alternator output cable from the center terminal on the isolator over to the "battery #1" terminal. This will connect the alternator to the start battery bank, and should allow the start batteries to receive a charge. In that way you could at least drive the coach without discharging the start batteries. The "coach" batteries, however, will not receive a charge from the alternator.

Re: Alternator Problem

Reply #3 – December 24, 2018, 01:29:12 am

WOW. Scary, but I'm not sure I understand all that you are describing.

You say that your engine start battery is not being charged, but you don't explain how you know that. Something is charging the battery set if it is at "12-something" Vdc.

I agree with what Chuck has advised (mostly). If your alternator/isolator has not been damaged or irreparably broken thus far, you should be getting some charge to your battery bank and I don't believe that you need to swap any wires around to get your unit to a reputable Alternator/Generator/Starter repair shop that understands DUVAC/remote sensing/dual battery banks/diode isolators. If your alternator is still capable of generating dc current, it will still replenish the battery set. It just won't bring the batteries up to their proper voltage.

You definitely do not have a correct DUVAC (dual battery sets) alternator installed for a two battery system with a diode isolator that isolated them. As Chuck has shown, what you have installed does not have the ability to remote sense and regulate two battery sets to the desired operating (driving down the highway) voltage.

The PO (and the shop that installed the replacement alternator) have conspired to set you up with a system that cannot work properly.

The "three studs" with the "AC" stamped into the case below them are the three stator fields (High Voltage Alternating Current) in the alternator. I think that you are saying that the right one of the these three studs is where you touched one end of a wire, drew an arc, caused the engine to lug down, the wire to heat up and the start battery voltage to jump up. That could and maybe already has caused irreversible damage to the alternator.

Get some direct, on-scene, assistance from a knowledgeable coach owner or a repair shop that understands DUVAC/remote sensing/dual battery banks/diode isolators.

HTH,
Neal

Re: Alternator Problem

Reply #4 – December 24, 2018, 07:54:48 am

Your alternator simply needs to be modified for DUVAC. Search DUVAC, there are lots of posts.

Re: Alternator Problem

Reply #5 – December 24, 2018, 10:04:33 am

Quote from: Neal Pillsbury – December 24, 2018, 01:29:12 am

I agree with what Chuck has advised (mostly)...you should be getting some charge to your battery bank and I don't believe that you need to swap any wires around to get your unit to a reputable Alternator/Generator/Starter repair shop...

Neal, funny how different people can read something, and interpret the subject matter differently. NOT saying your version is wrong...just slightly different from mine.

The OP just recently took possession of the coach. He stated neither he, nor the previous owner, could get the alternator to charge the batteries. I therefore assumed that the batteries had been fully charged before he received the coach, by some other external means, such as a portable 120V battery charger.

I got the impression that the OP connected the small mystery wire to the big POS alternator terminal ("the right one I believe"), hence my alarm. I don't know what would happen if he had touched the wire to the small right-hand "stator field" terminal. Would this produce the same result he described (reading on dash volt meter jumped up to 13 something)? I don't know...never tried it.

I also don't know how that particular alternator model is "excited" because the spec sheet does not address that fact. If it is "self excited" and will put out charging voltage without "seeing" any battery voltage on the output post, then I agree it should be providing some charging voltage to the batteries the way things are connected in the OP's photo. He says it is not working, because he is not seeing any indication of "charging" on the dash volt meter. I therefore suggested moving the alternator output wire from the (isolator) center post to the #1 battery post, just to insure that the alternator would "see" the actual start battery voltage, in case that is required to "excite" the alternator into action.

Anyway, we will all agree that the new owner needs to change something! We can best help him by suggesting different ways to get his coach charging system working correctly. One way, as Twig says, is to get the alternator modified to DUVAC operation. Or, replace the alternator. I am sure someone will mention other possibilities, such as replacing the isolator with a "smart" voltage sensing relay (VSR) or a manual HD switch. Might come down to whatever solution is easiest for the OP to get accomplished, given his physical location, OR whatever is least expensive.

Re: Alternator Problem

Reply #6 – December 24, 2018, 10:44:55 am

I would be curious to know if this coach has a BOOST switch. If it does, I do not think it would be operational. On my coach, the heavy cables to the BOOST solenoid come off the two battery posts on the isolator. I only see one cable on the isolator "battery #1" post. ??

Re: Alternator Problem

Reply #7 – December 25, 2018, 12:59:50 pm

Thank you all for your help. It looks like I'll be searching for an alternator shop to help me get this sorted out. I was able to get the rig home by buying a new 8D 1300 CCA battery and only using the brake lights and turn signals on the 3 hour drive. I've got it on a smart charger in the driveway for the time being. I guess I could also have used the booster switch, but figured I needed a new chassis battery anyways (the PO really abused the old one I'm afraid--it was reading < 3.0 volts when I went to pick it up).

This forum is a fantastic resource, thank you all again. I hope one day I'll be able to contribute as well.

Re: Alternator Problem

Reply #8 – December 25, 2018, 04:58:41 pm

Actually, you need someone familiar with RV wiring more than an alternator shop.

OR, if you have a digital voltmeter and don't mind rolling up your sleeves, we can walk you through it.

But, start by verifying with your alternator's wiring diagram that all terminals (like sense terminal and/or excite terminal if present) are hooked up properly.

Re: Alternator Problem

Reply #9 – December 25, 2018, 07:33:45 pm

Quote from: wolfe10 – December 25, 2018, 04:58:41 pm

Actually, you need someone familiar with RV wiring more than an alternator shop.
OR, if you have a digital voltmeter and don't mind rolling up your sleeves, we can walk you through it.
But, start by verifying with your alternator's wiring diagram that all terminals (like sense terminal and/or excite terminal if present) are hooked up properly.

Brett,
Probably not clearly, but, already pointed out:
"Hoplitus" has a replacement Leece Neville alternator that:

Is self-excited

Does not have remote sensing capability

Has an internal, non-adjustable voltage regulator

As far as I can find, can not be converted to remote sensing, at least using standard Leece Neville parts

In short, his present alternator is not presently compatible with two battery sets and a diode battery isolator design DC system.

[/list]

Most (but not all) alternators can be converted to remote sensing by "hacking" the alternator with an external voltage regulator. The downside to doing that is the voltage regulation system design as well as the individual component quality and the voltage regulator operation in a DUVAC/battery isolation application become suspect, not to mention all of the installation variables.

If one doesn't understand (thoroughly) what they are doing, it is easy to damage or ruin a number of batteries, not to mention alternators. We all need to remain aware that high DC current sources like alternators and coach batteries are very unforgiving and can do lots of damage in a hurry. If a knowledgeable coach owner is not right there to help "Hoplitus", a good shop that understands DUVAC/remote sensing/dual battery banks/diode isolators may be the most cost effective way to avoid all of that.
HTH,
Neal

Re: Alternator Problem

Reply #10 – December 25, 2018, 09:55:17 pm

Neal,

Thanks for the clarification.

Suspect this is how I would proceed given that info:
At the battery isolator combine wire from alternator B+ with wire going to chassis battery (just "add" the alternator wire to the chassis battery wire/lug). Just basically bypassing the battery isolator.

Start engine and see what voltage you get at that terminal and at chassis battery with engine at 1000 RPM.

Several reasonable "work arounds" to a remote sense alternator. Some with added owner controls.

Re: Alternator Problem

Reply #11 – December 26, 2018, 10:59:42 pm

Chuck, I haven't tracked down the isolator cables yet (it's been a little too cold and wet to get under the rig), but think battery 1 goes directly to the starting battery. I'll be sure to track them down when I get home (we're enjoying a bit of holiday cheer for a few days).

According to Neal, my current alternator cannot be easily modified for use with my diode isolator and two battery banks. After reading an earlier post in which Brett offered this solution to upgrading an electrical system--the use of an on/off Perko switch instead of an isolator--I think we'll go this route rather than replace the generator or try the external regulator hack. My interpretation is that by connecting the B+ and chassis battery to one lug and the house battery to the other, in the OFF position the alternator charges the chassis battery, while the ON position charges both chassis and house banks. Did I get that correct? With this fix, I'll abandon the diode isolator (for the time being, I"ll keep it just in case) and gain a little control over how my banks are managed.

This solution seems like a reasonable fix for us; we sometimes travel from CG to CG, in which case wouldn't need to recharge house batteries between stops. When we do camp off grid, we either start the trip with charged batteries from our home shore power, or could switch ON to charge up the house batteries on our way.

Would something like this be adequate?
250 Amp Battery Selector Switch| Wholesale Marine

My next step when I get back home is to connect the alternator output directly to the chassis battery cable and measure the voltage at the starting battery (yes, I do have a voltmeter). This should tell me if the alternator is still working.

I have a few other questions I'd welcome some advice on, regarding my converter and ATS. I'm guessing it's best to start new posts to keep issues separate?

Thanks again,

Byron (Hoplitus is a genus of wild bees)

Re: Alternator Problem

Reply #12 – December 27, 2018, 08:55:06 am

Quote from: Hoplitus – December 26, 2018, 10:59:42 pm

Chuck, I haven't tracked down the isolator cables yet (it's been a little too cold and wet to get under the rig), but think battery 1 goes directly to the starting battery. I'll be sure to track them down when I get home.

Byron,

I will be interested to hear what you find when you trace the isolator cables. You are probably correct - the big cable on the "battery 1" isolator post most likely goes to the start battery. This is the logical arrangement - to make the start battery "primary", and the coach battery secondary. By the way, that black cable on the "battery 1" post looks "non factory". You can tell the other two red cables (on the isolator) are factory original, because they have white numbered labels on them. The label number identifies the cable on the 12V wiring diagram that should be included in the Owner's Manual (that I HOPE you received with the coach).

The point I was making about the BOOST switch is this: on my coach there are two big cables connected to each of the isolator battery posts. From each post, one cable goes to the appropriate battery bank, and the other cable goes to the boost solenoid. When the dash BOOST switch is activated, the solenoid closes, and the batteries are connected into one single bank. Since I only see one big cable on your isolator "battery 1" post, I was wondering if your boost solenoid is even connected. That was why I commented.

It is possible that your boost solenoid is located in another place, like perhaps in the battery compartment? I don't know how your batteries are arranged, or even how many batteries you have. After you get a chance to trace the cables, you may find out if the boost solenoid is actually functional. Solenoids are easy to test - ask if you need any guidance.

As to the rest of your "PLAN", it sounds fine to me. Replacing your isolator with a mechanical switch is a great way to solve your current (Ha, Ha) problem. It gives you much greater control over your battery charging process, but it does require a bit more thought on the part of the operator. Sounds like you have a good understanding of how the system should be managed, so you will be fine with a manual switch. Just remember, when the battery banks are connected, it is possible to draw your start battery down so low that you would not be able to start the coach.

The switch you linked should work fine, or Brett may have other suggestions. He is a big proponent of manual switches, based on his extensive experience in the sailing world. Any advice he gives you is GOLDEN. Since you mention the ATS, I will tell you that I (based on Brett's comments) replaced our shore power/generator ATS with a manual switch, and it works great!

What did you do to your coach today IV

Blue Sea Systems also makes some excellent battery switches...for instance:

Amazon.com: Blue Sea Systems e-Series On/Off Battery Switch: Blue Sea...

Amazon.com: Blue Sea Systems HD-Series Heavy Duty On-Off Battery Switch:...

And yes, starting a new thread for each separate question is a good idea. Helps keep responses more on track, and makes it easier for members to "search" for the info in the future. When you start a thread, always try to make the title something that would be logical to search for, exactly like you did when you started this thread.

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Re: Alternator Problem

Reply #13 – December 27, 2018, 02:37:18 pm

Quote from: Chuck & Jeannie – December 27, 2018, 08:55:06 am

Just remember, when the battery banks are connected, it is possible to draw your start battery down so low that you would not be able to start the coach.

Byron,

The manual switch is good, an excellent way to use the alternator you have. For a few more dollars you could go with a smart isolator that automates the battery connections. This one (I have used with excellent results) has a boost option, you could replace your existing boost relay with this smart relay, or leave the old boost relay as a backup.

Cole Hersee 48530 Smart Battery Isolator 200A

Cole Hersee 48530 Spec sheet

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Alternator Problem

December 23, 2018, 11:14:43 pm

Re: Alternator Problem

Reply #1 – December 23, 2018, 11:29:33 pm

Re: Alternator Problem

Reply #2 – December 23, 2018, 11:33:57 pm

Re: Alternator Problem

Reply #3 – December 24, 2018, 01:29:12 am

Re: Alternator Problem

Reply #4 – December 24, 2018, 07:54:48 am

Re: Alternator Problem

Reply #5 – December 24, 2018, 10:04:33 am

Re: Alternator Problem

Reply #6 – December 24, 2018, 10:44:55 am

Re: Alternator Problem

Reply #7 – December 25, 2018, 12:59:50 pm

Re: Alternator Problem

Reply #8 – December 25, 2018, 04:58:41 pm

Re: Alternator Problem

Reply #9 – December 25, 2018, 07:33:45 pm

Re: Alternator Problem

Reply #10 – December 25, 2018, 09:55:17 pm

Re: Alternator Problem

Reply #11 – December 26, 2018, 10:59:42 pm

Re: Alternator Problem

Reply #12 – December 27, 2018, 08:55:06 am

Re: Alternator Problem

Reply #13 – December 27, 2018, 02:37:18 pm

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