First of all, let me state that I do not like working on electrical problems and electricity doesn't like me. (my DW's phone even turns off when she hands it to me)
OK, here goes. The rebuilt last fall Leese/Neville alternator on our coach, according to the dash gauge, was only putting out 11.5 volts. So, two days ago, with temps up in low 90s and high humidity I crawled under the raised bed and proceeded to remove the alternator. Red wire (+) off first. Then black wire (-) off. Then small red "exciter" wire off. This wire is SUPPOSED to be "dead" until the ignition key is turned on. I think I am OK. The key is out of the ignition and laying on the lower dash. YEAH!!! SURE!!! The exciter wire touched the black ground wire and suddenly I have sparks, smoke, and can't see squat!!! So why is the exciter wire live? I can only see about a foot of the now melted wire so where does this wire go?
Oh, by the way, the rebuilder checked the alternator and 14.4V. He said if the "exciter wire was "hot" all the time that it would draw down the battery. YUP, that was what was happening.
Norm,
The typical Leece/Neville DUVAC alternator requires TWO small wires. One is the "excite" wire, which is hot ONLY when ignition key is ON. The other is the "sense" wire, which is typically hot all the time.
Without knowing exactly what model alternator you are working with, hard to say what the single small wire does or where it goes. However, if it was hot with the ignition key off, it sure sounds more like a "sense" wire than a "excite" wire.
Do you know the model number of your alternator, or can you post a photo of the back side of your alternator?
Only number I could find was #102200 on the Leese/Neville nameplate, along with the 14V number.
I took pics of the back of the alternator, but haven't yet figured how to send them, so here is a description of what it looks like:
Far left (slightly large post) the negative post
Far right (large post) the positive post
About 1" to right of the negative post is the small post referred to as the "exciter" post.
Below this post is a recess with three small posts, with the right one slightly separated from the other two posts.
In all the years we have had the coach, with the alternator working correctly, we have never had more than the positive, negative, and the small wire to the alternator.
On my electrical schematic there is no mention of either the exciter wire or a sense wire. Not even lines or words.
My problem is that I was only a mechanical engineer and left the electronics to the electrical engineering dept.
Photos below (from Forum archives) of the typical L/N DUVAC alternator. Do these look like your alternator?
102200 is the voltage regulator number. Should be another plate on the alternator body somewhere with different model number.
Nope. Looked all over while the alternator was on the counter. Where else might it be hidden?
Any paperwork (that might show the model number) from when you bought it or when you last had it worked on?
If your schematic doesn't mention or show
either wire, why do you assume the small wire is a "excite" wire? It could just as easily be a "sense" wire. In fact, that would make more
sense (sorry - pun not intended).
There are some alternators that are "self excited". That is, they do not require external excitation to start outputting voltage. If this is how your mystery alternator works, then perhaps the small wire is indeed a "sense" wire.
Does your coach have a diode battery isolator?
The rebuilder yesterday showed us how the alternator did not charge without an exciter wire. Zero volts without and 14.4 volts with. He was quite knowledgeable about Leese/Neville and had rebuilt the same alternator about eight years ago.
Guess my getting the start battery cable crossed two years ago didn't help much either. Spark display and heat were nice to watch, tho.
No names here please---just dumbass will do.
Does your coach have a diode battery isolator?
Where would it be and what does it look like?
I don't know where it would be located on your coach.
Finned aluminum case with 3 or 4 large battery cable posts...something like the one below.
Mine is on the driver's side frame rail in the engine compartment. Someone built a "platform" above the frame rail to hold the 50A cord. Also, right under that is a small fan cooled tranny radiator. (nice, huh?)
Got to leave for awhile--Drs appointments for my cancer followup.
OK
I am back now, but it is raining "a little bit". We are in a Flood Watch until 7:00 PM tonight so no sense in going out in the downpour.
But I am still curious as to where the red wire (that smoked and melted) goes to from the alternator.
If you can't find the wire on a wiring schematic, then you will have to either physically follow the wire by hand to see where it goes, or use a circuit tracing device to locate the other end of the wire.
If you have a diode based battery isolator on your coach, and if your alternator does not have a "sense" wire connected, then I don't understand how your charging system works.
On some models of the earlier rear engine diesel engines the alternator had to be revved up to a little over a 1000 rpm to start charging. That has been too long ago for me to remember the wiring, they didn't have duvac alternators then. I know this isn't much help. I wonder what would happen if you hooked up an ignition hot to that terminal and tape off the small wire that is hot all the time.
My excite wire is about 9 in long. And runs from the fuel solenoid to the little post on the alternator.
I don't think that any other small wires are used.
Mike? Say what?? The wire goes from the fuel solenoid to which "small post"?
It would go to the SENSE terminal.
There is a voltage loss across the diode-based battery isolator. By having the sense wire on the chassis battery side of the isolator, the voltage regulator compensates for the loss. So for example alternator puts out 14.7 VDC. There is a .7 VDC loss in the isolator. The batteries then get 14.0 VDC.
Sob, whimper, cry, tear what remaining hair I have out!! My alternator DOES NOT have a post labeled "sensor.
Then it is not the correct alternator to be used with a diode-based battery isolator, as the isolator reduces voltage by about .7 VDC and the remote sense wire (to the chassis battery side of the isolator) compensates for the voltage loss in the isolator by telling the regulator what voltage is actually getting to the chassis battery. Yes, the sense wire can "come from" any location that shows chassis battery voltage-- does not need to be at any particular connection. On many, it is on the chassis battery lug of the battery isolator.
With engine at 1,000+ RPM, check voltage at alternator B+ to ground and then at the center lug of the diode-based battery isolator to ground and then at the two outer lugs to ground. Let us know what you find.
There ARE workarounds that are a lot less $$ than a new alternator.
Hey Brett. How do I know if I have a diode-based battery isolator alternator thingee??
Follow the wire from the B+ terminal of the alternator. Should go right to the center lug of the rectangular, finned diode-based battery isolator.
OK!! Except I have to remove a platform one of the previous owners installed as a place to coil up the 50A cord when the temperatures drop. Kind of tests one's patience, no??
Right now I just got the alternator in place and managed to thread the two bolts that hold the alternator in the bracket. Little different from some coaches. We have a rear radiator, so I have to assemble a platform under the bed (after raising the bed) and then drag all the necessary tools under with me. Drop one and I have to crawl out of that cavity, go outside and try to find the bolt or tool under the rear end of the coach--and hope the item didn't drop somewhere up in the framework.
Of course, lots of dropsy with my arthritic thumbs so lots of "calisthenics" climbing in and out at 83. For some reason I am not as spry/limber as I was last year. :)) :))
After dropping the alternator two times (just down on to the frame) I got a brain strain. I took the bolt that goes thru the slotted adjustment arm and chamfered the threads about 1/16x45*. Went right in and held the alternator while I fished around for the pivot bolt holes on the bottom side. Now back out to put the three belts on, tension and then tighten the bolts, then hook up the wires-----after finding out where the "little red wire" goes. I will need to cut cable ties and get the wire out of the protective ribbed sheathing.
Temp outside is 78* and my brain temp is 140* Wonder why.
Well, alternator is in. Small red wire goes from exciter post on the alternator down to the right post on the Powerline Model PL1-130-2
Duh. Didn't check which large red wire is under it on the post on the Powerline.
Just checked and the little red wire from the "exciter" post is on the same post as the black cable going to the starter?
Schematic found in our Excellent Forum Library. I added the "little red wire" that melted.
Note that the 2 GA "black cable going to the starter" connects directly to the 000 GA BLACK cable, which is connected to the POS (+) terminal on the ENGINE battery.
Therefore this black cable would be HOT all the time with ENGINE battery voltage.
Since the black cable is HOT all the time, it follows that the "little red wire"
would be HOT all the time with ENGINE battery voltage.
Something strange here. There is ANOTHER little red wire on the same post, right under "my" little red wire, and it disappears in the maze of wiring under the driver's side of the engine. So, what does THAT wire do? I guess I will have to trace it thru all the grease and 36 years of accumulated gunk.
If I reconnect a red wire from the (-) terminal to the "EXCITE" terminal then there should be a constant draw on the battery, should then cause my battery to see gradual voltage loss. And that is what has happened ever since we got the coach.
The red wire seemed to have been done very well at the factory, and not an add-on.
Does that little red wire that you found have voltage all the time or only when the ignition is on? Maybe it is supposed to have a duvac alternator and someone before you put on the wrong one.
Being clamped on the same post as the main battery cable I believe it has/had constant voltage.
But the Leese/Neville alternator is set up with an "excite" post on the back and thus should not be "hot" all the time, even when the engine and ignition are off.
So, should I run a new wire to the accessories position on the ignition switch?
No matter what, what is causing my system to only register about 11.5 volts?
Since you don't know the model number of your alternator, it's anybody's guess how it should be wired.
If you could determine the alternator model number, then it should be easy to find wiring instructions online.
I will call the rebuilder Monday. Thanks
It's very probable that one small post is the sense , and another is the excitement post.
I would use a fused jumper from 12v to each post and see which one turns on the charge circuit .
At the rebuilder's facility he showed me how, when zero voltage is on the "excite" post there is zero voltage being generated. When he applied 12V to the "excite" post the alternator output read 14.4 Volts.
How many post are there ?
I believe nitehawk said that the alternator is a powerline. This is a knockoff to a Leece Neville. I believe that some people who had worked for Leece Neville left and started the power line company. If your rebuilder understands a duvac alternator, then he can probably modify it to be a duvac alternator. You could take a volt meter and check the large positive terminal with the engine not running and it should have no voltage. Take a jumper wire from a 12 volt source to the excite terminal with the engine running and see what the voltage is then. I do think that you will have to have it modified in order to get proper charging to the engine and house batteries. Wish I was close, I would come and help you.
Sorry Red, my alternator says Leese/Neville right on the nameplate. The isolator is a Powerline Model PLI-130-2.
The rebuilder demonstrated that my (+) terminal on the alternator put out ZERO voltage until 12V was touched to the Excite terminal. Then He got 14.4 volts from the (+) terminal.
Most vehicle alternators use an "excite" or other means to get the alternator started. Usually it is part of the charging warning lamp system. Having a failed bulb can cause the alternator to "not" turn on. It is possible that the excite circuit is fuse protected. Most likely it is powered from the ignition for fuel stop circuit.
Sorry I didn't understand the power line regulator.
Let us know if you are able to determine the alternator model number.
DUH! Totally forgot to call yesterday. Too many things going on here, but none serious. Just forgetful on my part.
I called this afternoon. Greg will get back to me, hopefully tomorrow (busy, busy).
So today I proceeded to dismantle and clean ALL the cable connections and then reconnected them After I get all done, protective anti-corrosion spray.
Voltage went up a little bit on the house battery gauge after cleaning and reassembly. 12.6V
What do you mean by "the house battery gauge"? Are you talking about the instrument panel volt meter, or another gauge?
Have you tried measuring the voltage directly at the battery posts?
Yup. Voltage went from 12.2 up to 12.6 on my little red voltage test instrument. Not a heck of a lot but nothing was different other than newly cleaned wire ends and contact points like battery terminals.
Tomorrow is predicted to be wet and sloppy weather with storms off and on tomorrow and Thursday.
12.2 and 12.6 is a huge difference when talking battery voltage not being charging
OK, here is the info I got from my rebuilder: Alternator is a Leece-Neville 130A Model 2670LC
Hope this helps. Isolator is a 130A also.
From post #22. When the alternator is reinstalled, let us know the voltages.
In looking up the specs for your alternator (so I presume Prestolite bought Leece Neville):
2670LC PRESTOLITE LEECE NEVILLE 2600 12V 130A BRUSH ALTERNATOR (https://www.peivinlookup.com/Category/A0012670LC)
PRESTOLITE LEECE NEVILLE 2600 12V 130A BRUSH ALTERNATOR
SPECIFICATIONS
Brand Name PRESTOLITE ELECTRIC Condition New
Voltage (V) 12 Brush or Brushless Brush
Output (A) 130 Ignition terminal No
Polarity Insulated return Sense terminal No
Rotation Reversible Lamp terminal No
Mounting type J-180 (Long) Pulley fitted (Type,OD) tbc
Field isolation terminal No Overhang position (mm) tbc
Multipower terminal No Product family 2000
Excitation type Self excite EAN code 5052629013812
Regulator included Integrated
SO. that just seems to add to the confusion. Self exciting or needs 12 VDC excitation??? No sense terminal???
As I mentioned earlier, that alternator may work very well, just NOT with a diode-based battery isolator.
Easy to test: Move the battery cable for the chassis battery lug on the battery isolator to the center lug of the battery isolator that is directly connected to the alternator B+. What is the voltage now?
If it 13+ VDC, there are some relatively inexpensive "work arounds". I did one of these "work arounds" a long time ago, not because of a failed isolator, but because I like KISS (Keep It Simple Stupid). I used a Perko simple ON-OFF marine battery switch. Wire from alternator B+ and wire to chassis battery to one lug of the switch. Wire to the house battery to the other lug. Switch off, chassis battery gets charged. Switch on, both banks get charged but can discharge as one. Also serves as an excellent battery combine.
Mount is somewhere that you can easily get to inside the coach or in a basement compartment. On our 1993 U240, I mounted it on the vertical wall at the foot of the bed next to the other electrical equipment. Raise the bed dust cover and it is right there.
What I don't understand is that the original isolator came with the coach back in '89. (the rust surrounding the isolator and frame mounts give that impression of age. No witness marks from anything else mounted there.
The alternator came with the coach when we bought the coach about12-14 years ago.
Never had any problem with this alternator, even the first rebuild. But, after some dumbass (no name here, please) in the dark of the storage place, accidently hooked up the second start battery back-asswards. WOW!! Lots of spark and smoke there for about 10 seconds!!
So, now 1 newly rebuilt (and very recently double checked) anternator puts out 14.4 volts on the test stand but only reads about 11.5 on the coach dash gauge (a needle indicator not an idiot light).
So, what is the opinion? Did I blow the isolator? If the excite post wired to the engine battery post worked all these years, should I just hook a new (untoasted burnt) wire from engine bat post to the excite post and see what happens?? {The old wire got cremated because the hot "excite" wire touched the black ground wire the dumbass had removed off the alternator and didn't know the excite wire was HOT!!}
Try Brett's idea of hooking the alternator B+ cable directly to the engine battery post on the isolator. This takes the isolator out of the equation. You would then be able to use a short excite wire from the B+ post on the alternator to the excite post and see if it starts charging.
Now I am really confused. Brett, I looked up the alternator on your last post. It shows two yellow wires connected to two of the small posts on the lower recess on the back of the alternator but NO "exciter" post at all.
My alternator doesn't have those two wires but does have those three small posts AND the "exciter" post above them.
Now I am worried that if I try your idea of changing the wiring I might "blow" the alternator or some other item.
Does it look more like the alternator in photo below?
Leece-Neville Alternator 2670LC (543-10347) | eBay (https://www.ebay.com/itm/316254981981)
Your alternator has the older model voltage regulator. See your Reply #2 in this thread. It was apparently later replaced with a different regulator.
Alternator: Regulator change 102200 to 103450 - All Things Foretravel (https://www.allthingsforetravel.com/2020/02/24/alternator-regulator-change-102200-to-103450/)
You will NOT hurt anything by directly wiring the alternator B+ to the wire to the chassis battery.
This will just remove the diode-based battery isolator from the equation (the isolator could be failed and if working correctly, it WILL have a .7 VDC voltage drop). That voltafge drop across the isolator is the reason for the remote sense wire (which tells the regulator what voltage is reaching the chassis battery.
So what should I do? Make a jumper wire from the "excite" post to the center smaller post just below?
If you hook up the B+ directly to the chassis battery cable at the battery isolator end (just move the chassis battery cable and ADD IT to the cable from the B+), then if you do need 12 VDC to the excite terminal (not saying you do or don't, as the description and what you see are different) then a short jumper from alternator B+ to the excite terminal will do it since you not have chassis battery voltage at the B+ terminal.
Anyone else concur/disagree???
Brett is saying to move the chassis battery cable from its post on the isolator to the center terminal on the isolator and then try it to see what voltage you have with the engine running.
Yes, thanks for the clarification, I went back and added:
B+ directly to the chassis battery cable
at the battery isolator end
Got it, but I have an issue with all the standing water on our drive and on the lawn. We got 2-1/2" of rain this afternoon, and more predicted for tomorrow.
So, knowing that water and electricity don't mix, I will hold off awhile.
How do I know? When I was about 12 my farmer uncle told me and my cousin that the electric fence on the dew covered clover hay field wasn't on. (He was wearing rubber boots) My cousin and I started to straddle the low electric wire and discovered that my uncle had lied. My voice didn't come back down for two years. :)) >:(
Was going to go out and start moving wires around this morning. BUT!!!! The humidity is way, way up there. I thought I saw a school of small minnows go by my office window a few moments ago.
So am putting off any working outside until maybe this afternoon, altho rain is predicted--AGAIN.
Just wear rubber boots like your uncle ;D
Just reading your post , my original alternator was a leece Neville 160 amp output with this duvac system that I've read about , anyway after lengthy searching ,I came up with a leece Neville alternator which I was told was the correct one , so I bought it had it shipped to UK probably 4 or 5 year ago now , it looked identical but it was only a 120 amp version so I knew it was wrong , but I wasn't too bothered I thought oh well IL fit it anyway and when i started the engine obviously it wouldn't charge , I think it's because of the battery isolator ,and because there is no direct power direct from the battery to the alternator it wouldn't self excite hence why the duvac system is important , a normal vehicle without a separate battery system like all the rvs have would be connected direct to battery , anyway someone said to me all I need to do to get the alternator charging was to run a hot wire onto one of the spare terminals I have on the alternator which I did and as soon as I started the engine all I did was strike one of the smaller terminals with a hot wire just quickly and that was enough to get the alternator charging , so once I discovered that ,rather than go through all the hassle of sending the alternator back and getting the correct one, cause I can't really remember who's fault it was mine or whoever I bought it from now but what I did in the end I connected 1 wire to the terminal that set the alternator charging and ran it all the way underneath up into the dash and connected to a spring return switch and the other to a hot wire , so all I have to do now is start the engine ,press the switch just for a fraction of a second and let go and that gives me just enough power for the alternator to start charging, and it will stay charging till I switch engine off , and the next time I start the engine I have to do the same, it works fine ,I was a bit concerned that it was only a 120 amp alternator, but it is plenty I have no issues with the system at all works fine even if I was driving at night with headlamps on there is still enough power to keep the batteries fully charged ,and also I do have the solar panels fitted on the roof which I bought from windy nation ,was recommended this company by one of the forum members ages ago , IL take a photo of my alternator in a bit ,I mean for all I know it has got a duvac system fitted to it without my knowing and maybe if I wired it up differently it would start charging without having to flick the switch , mind you I have done this so many times now that it just comes naturally , turn the key flick the switch , at first I would sometimes forget until I looked at the voltmeter , IL send this and then I will take a photo of my alternator and upload , I can't even see any numbers on it , maybe the numbers are there but I have over the past few years sprayed with water resistant spray which contains PTFE ,which helps keep moisture out , I'm always going around with spray grease ,it's probably had that many coats of it that it's just covered the label maybe ,IL have a look in just a sec and send the photo kev
Well, I did what Brett told me to do. I connected the alternator cable to the black #2 battery cable, along with the two red wires.
Then I went in the coach and started it up.
YAHOO!!!! Absolutely amazing. My meter now reads 14.3 volts!!
So now I am waiting on the selector switch to mount on the foot of the bed. (here tomorrow)
Got to go shopping for 4Ga cable and ends later today.
Thank you Brett and all the rest of you for helping a dumbass (no name here, please)
How times change-- only 36 years old and the battery isolator craps out. What is the world coming to?
Ah brilliant I'm glad you have sorted it out ,IL still send a photo of mine , cause maybe it does have a duvac system on it and I don't know maybe ,that's why it works when I flick the switch on the dash ,but would mutch prefer if I could wire it up so I don't have to flick a switch on the dash , cause occasionally I do forget to flick the switch and then I suddenly remember when I see the voltage has gone down , just been doing a touch of welding , I'm just packing up and IL send that pic of my alternator ,hope you get well soon
Kev,
If you want some help with the correct wiring for your alternator, I would suggest you start a new separate thread on that subject. It will help if you can post some photos of the back side of your alternator, showing the wiring terminals, and a photo of your battery isolator. Getting the alternator hooked up correctly isn't rocket science, but depends a lot on the alternator model and battery charging setup in your coach.
Here is the switch I used: PERKO Inc. - Catalog - Battery Switches - Medium Duty Battery Disconnect... (https://www.perko.com/catalog/battery_switches/150/medium_duty_battery_disconnect_switch/)
Rated for 250 AMPS Continuous, 360 AMPS 5 Mins. Intermittent.
Wiring:
Wire from alternator B+ and wire to chassis battery to one lug.
Wire to house battery bank to the other lug.
Yeah I get that , now thanks ,I've been thinking about that one for a long time, as long as that alternator has a direct source of power from the house batteries it will automatically excite , yeah that makes sense cheers ,
Here is a pick of the back of my alternator you can see where I have attached the thinner 18 gauge wire the one that I've run to the spring switch on dash that would probably be the b plus terminal you mentioned ,is that correct please,
No, the B+ is the large lug on the right marked +. It is the 12 VDC positive that goes to the isolator center lug (assuming you still have the diode-based battery isolator).
Looks like you probably have the same (or similar) type alternator model as nitehawk.
The terminal you have your "thinner 18 gauge wire" attached to is called a "AC tap". It is definitely
not a "excite" terminal.
I don't know how your "spring switch on dash" works to turn on your alternator. Not a normal setup, but if it does the job.........why not?
Perhaps this video will help....or not.
https://www.youtube.com/watch?v=hJB7cMeLwbI
Yeah will watch now thanks alot
Yeah just watched the video briefly very interesting have subscribed to that channel , Il watch it later when not doing anything else I can concentrate better ,mutch appreciated thankyou
Yes I do have the same set up as nitehawk , with the diode battery isolator ,it is attached to the chassis drivers rear, and yes it works fine with the switch,it just needs a mili second of power and you can see the voltmeter go up and working fine , so IL leave well alone at the moment , I find electrics very interesting,