Alternator wiring.

Topic: Alternator wiring. (Read 945 times) previous topic - next topic

Alternator wiring.

April 14, 2021, 11:55:58 am

Please don't judge......

Been dealing with low charge from alternator since I got Alice.
Finally got looking at it and I only see two charge cables attached.
See attached.
This CANT be right.

Service tech says he saw wires hanging down while underneath.
What color goes where?

Re: Alternator wiring.

Reply #1 – April 14, 2021, 12:03:39 pm

Should be numbers on the wires-- check against your wiring diagram.

OR post the wire numbers and someone else with a diagram can look them up.

Re: Alternator wiring.

Reply #2 – April 14, 2021, 12:05:44 pm

Moby,
We gonna need more info and some better photos.

1. Are you still running the original type battery isolator?
2. Is your alternator original, or has it been replaced?
3. Do you have any paperwork describing your alternator make or model?
4. How many "extra" wires are hanging down below the alternator?

Can you get some better photos of the back end of the alternator? Pull back a little so it is easier to "get the big picture".
Would be helpful to see all of the terminals, and also a photo of the id plate (or sticker) on the alternator.

Re: Alternator wiring.

Reply #3 – April 14, 2021, 12:07:13 pm

Looks like someone did some creative wiring for the DUVAC system your coach had OEM. If you still have the battery isolator then you need to have all 4 wires hooked up. One of the small wires goes to the ignition and the other goes to the sense side. Now you will have to trace which wire is which as the color may lead you down the wrong road.
Like Chuck above we sure could use some more info and better pics.
Mike

Re: Alternator wiring.

Reply #4 – April 14, 2021, 12:29:21 pm

Quote from: Chuck & Jeannie – April 14, 2021, 12:05:44 pm

Moby,
We gonna need more info and some better photos.

1. Are you still running the original type battery isolator?
Yes, as far as I know

2. Is your alternator original, or has it been replaced?
Been replaced.
3. Do you have any paperwork describing your alternator make or model?
Sadly, no
4. How many "extra" wires are hanging down below the alternator?
Tech on lunch, will ask on return

Can you get some better photos of the back end of the alternator? Pull back a little so it is easier to "get the big picture".
Would be helpful to see all of the terminals, and also a photo of the id plate (or sticker) on the alternator.

Can't find the id plate.

Re: Alternator wiring.

Reply #5 – April 14, 2021, 12:42:39 pm

Best I could do, for right now as far as new pics.

If it helps, I've located one small wire, yellow in color, terminated at the LEFT heavy duty wire. Most noticeable in the last picture.
By length, I'd guess it went to the left most smaller terminal.

Re: Alternator wiring.

Reply #6 – April 14, 2021, 12:54:51 pm

I can't tell anything from those photos. Sorry.

Without some way of identifying your replacement alternator, any advice anybody gives you is just shooting in the dark.

See if the tech can get in there and somehow clean up the area around the small terminals. It would help to know if any of them have any kind of marking. Looking for something like a "S" or a "I" or "SENSE" or "IGN".

Would also help to know where the yellow wire is terminated on the other end. Also where the "extra" wires go.

As a last resort, you may need to remove the alternator and get it out on a bench where you can get a good look at it and make positive ID.

Re: Alternator wiring.

Reply #7 – April 14, 2021, 04:21:25 pm

Sorry about the poor pictures.
Perhaps a schematic would help.

(two wires from wiring harness)
Yellow Y1
Blue B1
(both hang free)

Terminal T2 T3
(T1)

REAR OF ALTINATOR

T5 T4

T5 has a large red wire attached to it, T4 Has one large Red wire attached to it. (battery lead) it also has a small (20G?) yellow wire attached to it. Y2
Y2 is only long enough to connect to T1.

I am assuming Y2 is the "exciter" or "IGN" wire as it would constantly have a 12VDC charge on it (assuming battery is charged).
I am also assuming it goes to T1 as thats the only terminal it can reach.
The two other wires (Y1 + B1) are, I'm assuming are the sensor wires - the wires that tell the alternator which bank needs charge based on the voltage delivered. I can (but have not yet) verified that they normally have some charge on them but present 0 VDC when one of the battery's are disconnected. I will do this and hope to find out which color wire goes to which battery bank..
This being the case, I only need to find out which sensor wire goes where.
Yes, I plan on having my much more flexible son in law look for definitive labels.
Other suggestions?

Re: Alternator wiring.

Reply #8 – April 14, 2021, 05:06:07 pm

Other than reading the numbers on the wires, easy to differentiate between IGN from SENSE.

IGN will only have 12VDC between it and chassis ground (any clean metal on the engine) with the ignition ON.

SENSE will have exactly the same voltage as the chassis battery all the time.

Again, we don't now if this is an OE alternator or some other variant that is wired differently.

Re: Alternator wiring.

Reply #9 – April 14, 2021, 07:00:31 pm

Given that Y2 is directly connected to a battery cable, I'm gonna assume its a sense wire.
Brett, I totally get your caution here, and I plan on using due diligence to figure this out
NO GUESSING.

But, if I have to pull the unit. How hard is it to remove?

Re: Alternator wiring.

Reply #10 – April 14, 2021, 07:19:32 pm

Pulling the alternator is not complicated, but can be difficult, depending on how tight the mounting bolts are. Remove the belt, remove the cables on the back, remove the mounting bolts, remove the alternator.

If you start connecting wires (carrying voltage) to the screws on the alternator without knowing what you are doing, you can easily cause damage to the alternator or the voltage regulator.

Re: Alternator wiring.

Reply #11 – April 14, 2021, 07:43:41 pm

Can you be specific on your symptoms, like voltage. Also measure voltage at all three of your isolator.

Also nice for me to know your first name.

Re: Alternator wiring.

Reply #12 – April 14, 2021, 07:50:41 pm

You have the rear radiator which complicates the removal.

Re: Alternator wiring.

Reply #13 – April 14, 2021, 08:03:20 pm

Quote from: Barry & Cindy – April 14, 2021, 07:43:41 pm

Can you be specific on your symptoms, like voltage. Also measure voltage at all three of your isolator.

Also nice for me to know your first name.

Its Rich.
Symptoms are simple....battery's are not charging unless I run the genny.

Re: Alternator wiring.

Reply #14 – April 14, 2021, 08:06:37 pm

Quote from: Chuck & Jeannie – April 14, 2021, 07:19:32 pm

remove the cables on the back

Well.......
3/5 ths of THAT is done!

Anybody know if the idler pully right next to the alternator is a spring loaded tensioner ?

Re: Alternator wiring.

Reply #15 – April 14, 2021, 08:07:25 pm

Quote from: red tractor – April 14, 2021, 07:50:41 pm

You have the rear radiator which complicates the removal.

How so?
Looks accessible from up top.

Re: Alternator wiring.

Reply #16 – April 14, 2021, 08:10:22 pm

If you look in the back of a side radiator coach you will immediately see what I mean.

Re: Alternator wiring.

Reply #17 – April 14, 2021, 08:22:54 pm

Quote from: red tractor – April 14, 2021, 08:10:22 pm

If you look in the back of a side radiator coach you will immediately see what I mean.

Yes - pretty easy with no radiator in the way.

The idler pulley on my C8.3 is spring loaded. Use a 1/2" breaker bar to release the tension (which is considerable so watch yer fingers).

Re: Alternator wiring.

Reply #18 – April 14, 2021, 08:48:29 pm

Ok.
So the question becomes, if I HAVE to pull the alternator are y'all saying I HAVE to pull the radiator?
Or, it's just harder with a rear radiator?

Re: Alternator wiring.

Reply #19 – April 14, 2021, 09:00:59 pm

Just harder. No need to pull the radiator just to remove the alternator.

Mike

Re: Alternator wiring.

Reply #20 – April 14, 2021, 10:14:20 pm

Quote from: Moby – April 14, 2021, 04:21:25 pm

T5 has a large red wire attached to it, T4 Has one large Red wire attached to it. (battery lead) it also has a small (20G?) yellow wire attached to it. Y2
Y2 is only long enough to connect to T1.

I am assuming Y2 is the "exciter" or "IGN" wire as it would constantly have a 12VDC charge on it (assuming battery is charged).
I am also assuming it goes to T1 as thats the only terminal it can reach.

The two other wires (Y1 + B1) I'm assuming are the sensor wires - the wires that tell the alternator which bank needs charge based on the voltage delivered. I can (but have not yet) verify that they normally have some charge on them but present 0 VDC when one of the battery's are disconnected. I will do this and hope to find out which color wire goes to which battery bank..

Rich,

Your alternator has two large red cables attached. First order of business is to determine which one is the ground cable. Easy to do - just follow them both to see where they lead. The ground cable is usually short and grounds on the engine block near the alternator. The other cable will be the B+ (charging cable) that goes to the center post on the battery isolator.

You think the big red wire on the T4 lug is the charging cable, which may or may not be true. However, even if it is true, that wire will not be constantly HOT because it connects to the center lug on the isolator, which should not show any real voltage (unless alternator is turning). With engine off, only the two outside posts on the isolator will read actual battery voltage (unless the isolator has failed).

You think that the small yellow wire is the "exciter" or "IGN" wire, because it is connected to one of the large lugs and can only reach T1. This is incorrect. The "excite" wire on a DUVAC alternator must be connected to a source that is only hot when the ignition switch is turned to the ON position. Connecting the "excite" wire to a constantly hot source would not work.

You think the other wires (Y1 & B1) are the "sensor wires - the wires that tell the alternator which bank needs charge based on the voltage delivered." This is also incorrect. IF your alternator is DUVAC it will only have one "sense" terminal. There will only be one "sense" wire. That wire will be connected to a source that reads the START battery bank voltage. It is usually connected to the START battery post on the isolator, but may be connected directly to a POS (+) post on a start battery. Either way works fine.

Your statements above indicate you may not be completely clear on how the DUVAC alternator works. Of course, we don't even know yet if you have a DUVAC alternator. But in case you do, the thread linked below will help explain how it should work. (If it turns out you do not have a DUVAC alternator, this discussion will go off in a completely different direction.)

What is DUVAC?

Re: Alternator wiring.

Reply #21 – April 14, 2021, 10:42:49 pm

Chuck,
I'm starting (see what I did there?) to understand more and more.
I'll check both large lines to see if ones a ground and see if B1 or Y1 are the ignition wires.
Still don't understand why there are three small terminals, but patience.

Just flushed the antifreeze out of the water lines, and freezing temperatures forecast for tomorrow. Gotta address that first.

Re: Alternator wiring.

Reply #22 – April 14, 2021, 10:50:35 pm

Quote from: Moby – April 14, 2021, 10:42:49 pm

Still don't understand why there are three small terminals...

Many alternators have several small terminals that are not to be used except under special circumstances. This is why it is essential to determine the correct wiring hookup for your specific alternator model.

Link below to a little light reading:

https://www.prestolite.com/literature/tech/alts/TSB-1057_Universal_alternator_wiring.pdf

Re: Alternator wiring.

Reply #23 – April 15, 2021, 08:49:28 am

Rich,

You have a confusing alternator problem. Here is one possible explanation that we have seen several times on this Forum. Your coach was factory equipped with a DUVAC alternator which was specifically designed to work with the factory installed diode based battery isolator and two battery banks. Your original DUVAC alternator most likely had both a "sense" wire and a "excite" wire. So far, so good.

At some point your factory alternator was replaced...probably by a mechanic (or owner) who was not familiar with the DUVAC alternator and the two battery bank electrical system on your coach. This mechanic may have used some no-name generic replacement alternator that he thought would work fine. He thinks "It's just like replacing a truck alternator". So he disconnects all the wires hooked to the old DUVAC alternator, pulls it out, installs the new alternator, and connects the large charging (B+) cable and the ground (NEG) cable. Just like he would on a truck. However, since there is no obvious place on the new alternator to attach the two small wires, he just ignores them and lets them hang down (worst case) or he wraps them with electrical tape and tucks them away (best case).

The happy coach owner drives off thinking he has a nice new alternator. Sooner or later he will discover "it is not working right". In some cases, it might not charge at all because it never turns on (needs a "excite" wire connected). Note: the alternator may come with a short "excite" jumper wire. The instructions will say to connect the jumper between one of the small terminals and the large (B+) charging post (sounding familiar?). On a single start battery truck engine, this will work. It will not work on coach with two battery banks and a isolator. Sometimes the new alternator will be "self excited" and it will turn on and try to charge the batteries, but will not fully charge them due to voltage loss going through the isolator (needs a "sense" wire connected). Sometimes the "mechanic" will try hooking the two small wires to one of the small terminals on the new alternator without knowing what they are for. Often results in damaged alternator, or melted small wires and possible engine compartment fire hazard.

I think this is the sort of scenario that has got you where you are. Once we have a positive identification of your alternator, we will know how to proceed. It may mean simply attaching wires correctly. If your alternator is non-DUVAC there are ways to make it work. Or, you may decide to make some changes to your setup...but you should not do that until you positively ID the alternator (and make sure it is actually functional).

Re: Alternator wiring.

Reply #24 – April 15, 2021, 08:59:30 am

Or, if I can't identify, get a new alternator.
I mean, if it's a hassle to pull why put back a used part?

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