# The infamous blue exciter wire!!!



## RyanBabros (Jul 2, 2010)

I need EVERYONE'S input:

1. Is there anything in the blue exciter wire circuit; instrument cluster, ignition switch, etc that can fail causing a complete failure of the alternator?

2. If I supply 12 volts to the exciter wire alternator terminal from the coil will it cause damage to the voltage regulator? I was told that doing so without adding a bulb in line to reduce voltage it could possibly cause the voltage regulator to fail, is this true?

3. What beer should I drink after I finish the repair? :laugh: :beer: :beer: :beer:x how many people help me!!!


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## antichristonwheels (Jun 14, 2001)

1. Is there anything in the blue exciter wire circuit; instrument cluster, ignition switch, etc that can fail causing a complete failure of the alternator?


If there isn't 12V present on the blue wire, the alternator will not charge, so yes. A break in the wire or where it feeds thru the diode in the instrument cluster and the alternator will not charge.



2. If I supply 12 volts to the exciter wire alternator terminal from the coil will it cause damage to the voltage regulator?

No, but...

I was told that doing so without adding a bulb in line to reduce voltage it could possibly cause the voltage regulator to fail, is this true?


You need a diode in line to allow current flow only to the alternator.


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## RyanBabros (Jul 2, 2010)

antichristonwheels said:


> 1. Is there anything in the blue exciter wire circuit; instrument cluster, ignition switch, etc that can fail causing a complete failure of the alternator?
> 
> 
> If there isn't 12V present on the blue wire, the alternator will not charge, so yes. A break in the wire or where it feeds thru the diode in the instrument cluster and the alternator will not charge.
> ...


-SO, 12v is absolutely necessary to run the alternator? Not the 10v I am getting now? I just want to make sure that I dont take out my alternator again. Something caused the reman I just recently bought to fail almost immediately. I did two things: ran the car with the factory harness connected to the alternator(2 red charge wires/1 blue exciter) and then I tried running 12v to the exciter at the connector. One of the two things I did killed it. I know it. Pretty slim chances I got a junk alternator. Any ideas?

-If the Diode with the instrument cluster fails will it or CAN it cause the alternator itself to fail internally? Normally this diode would keep the battery from draining?


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## Seax_Smith (Jun 1, 2007)

Worked in Parts for a lot of years.... junk remans (starters, alts, etc.) are sort of common depending on the reman company. [the really cheap remans come form palces which gut the core, slpa in new intrenals and ship them out WITHOUT checking anything].

There isn't much in an alt to go bad. Usually it is the brush pack (aka regulator).If you got a bad reman, just go back and get another one. Once you get one that works, get a second brush pack for it which is a lot less expensive than a new alt.

Have you checked the voltage BEFORE the diode in the cluster?

If you are really stuck: use a relay and battery power.

Control current = any Black/Yellow wire (cross over relay power) this will cut out when you try to start, just like the head lights, but will be fine while you are running, so you will be charging as normal OR use the 10 v you are getting out of your blue exciter wire (10 v should be enough to trip most relays)

Control ground = body ground anywhere

Primary power = Battery -> inline fuse -> diode -> alt.


FIY: alt in my current daily has seen use in a daily for over ten years, granted I have repalce the brush pack several times, but the alt itself is still strong. Brush packs for me kind of suffer becasue of my forward lighting (2x 130/90W H4's, 2x 100W H3's, 2x 100 W H3's in aftermarket fogs)


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## WaterWheels (Aug 14, 2005)

First a correction to make regarding what's in the instrument cluster or exciter circuit. There is no diode, two resistors but no diodes. The alternator does not require 12v to get it charging and the resistors are there, I believe, so that the “battery” light does not come on or flicker everytime the voltage drops below battery voltage for a few seconds or so. Lets say the exciter wire did provide battery power to the regulator. That is about 12.6V in most cars. So everytime you flipped on some heavy draw items, high beams, heater blower on high, brake lights and rear window de-fogger, your battery warning light would either come on for a short period or flicker. If the exciter power is say 10v it would not do that until the alternator or battery power drops below that level. Diodes on the other hand are one-way valves for electricity. In the exciter circuit you need power to be able to flow both ways so it does its job.

I don't believe supplying 12v to the regulator via the exciter wire all the time will damage anything, but it could be possible. As pointed out, rebuilt alternators are very much a hit or miss situation as not many places do a good job of rebuilding. My thoughts are that there as say three people working in a company. Say each one has 10 or more alternators which come to them to rebuild on a given day. Each begins work on an alternator and the rest are cleaned, painted and a sticker slapped on and boxed up for sale. It's no problem as the 9 they just cleaned and resold will be back sooner or later again. So it is possible it is/was bad from the start, it does happen.

If you take a multi-meter reading of the battery power with the engine off and everything else turned off and then start the engine, bring it up to say 1500-2000RPM with a few electrical items turned on and the voltage reading is the same or less, it is not charging. That or the cables, connections or battery are bad. You can not do a full field test on these alternators if I remember, so the only cheap check is to replace the regulator. If no improvement the the alternator needs to be checked out.


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## antichristonwheels (Jun 14, 2001)

Connect a wire from the 12V at the coil to the exciter without a diode. If you have a carb and mechanical pump the engine will not turn off...

If the alternator didn't need the 12 V the wire would not be there.

I watched someone start a Golf in cold weather and not rev it a bit to get it charging, came in the house to let it warm up. A few minutes later the car died because the battery was drained due to the alternator never coming on.

When I have a problematic exciter circuit I run a wire from B+ to the exciter lug with the diode inline done.


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## WaterWheels (Aug 14, 2005)

antichristonwheels said:


> Connect a wire from the 12V at the coil to the exciter without a diode. If you have a carb and mechanical pump the engine will not turn off...


OK, not to insult you in any way, I hope, but it only takes a little common sense and knowledge of automobiles to understand why that happens. Alternator turning, electricity comes out of the terminal that the exciter wire connects to (that is one reason the battery light works the way it does) and runs to the coil terminal (15), turn off the ignition and because the alternator is still sending power to that terminal, the engine keeps running. Carburetors do not require any electric power to work, just low pressure created by the turning engine. For that reason, and others too, you should not connect a wire between these two locations.



antichristonwheels said:


> If the alternator didn't need the 12 V the wire would not be there.


I could really get sarcastic with this one but will hold back as that is not the purpose of this response. I mean think about all the "If it didn't need _______, then ______ would not be there." little examples you can say about items in a car. Fact is it does not need "12v" to become excited. Only a few volts would most likely be enough to excite the field and get it working. In fact most times there is enough residual electricity that if only turned off for a short time, the exciter really would not be needed. Once the charging process starts the regulator monitors voltage and only allows the alternator to produce the amount it needs to to maintain the battery by varying stator current. It is as simple as looking at a wiring diagram and noting that the exciter circuit has a light and two rectangle shaped things also in the wiring. Match those shapes to the "key" and it will tell you they are resistors, easy. IF you need me to post a diagram, for this vehicle or in geneeral, of the exciter circuit and charging system I can, but you "should" be able to do that on your own.



antichristonwheels said:


> I watched someone start a Golf in cold weather and not rev it a bit to get it charging, came in the house to let it warm up. A few minutes later the car died because the battery was drained due to the alternator never coming on.


That is only a testimonial to maybe one or two things. One being the battery is not in very good shape or there were a lot of electricity consumers turned on (fan on high, rear window defroster on, seat heater, etc) and the second, the alternator requires a little work as it should not by design require the engine speed to be increased for it to begin charging. Yes it is talked about in the manual, but if you read it as written and not try to make it mean something else, it is telling you if it does not begin charging "after" the engine speed is increased there could be a problem. The manual does not, none do, inform you to start the engine and increase the engine speed "in order to" get the charging system working.


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## antichristonwheels (Jun 14, 2001)

please everyone remove the blue wire. In fact remove the exciter lug from the alternator. 
let us know how long the battery lasts.

Regardless of what any manual says or doesn't say the Bosch or Motorola alternators on our cars will often not begin to charge until the rpms blip up

The OP asked about connecting to the coil and I don't know where the carbs and strom comment came from.

"residual electricity???" :facepalm: Don't worry about being sarcastic, or insulting me, Mr. Oersted.


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## Seax_Smith (Jun 1, 2007)

Battery light coming on and staying on at start up unless the throttle is blipped..... my exprerience is that it is a true statement for about 85% of Mark II's I have ever encountered. Not how VW designed them, I am sure, but I am equally sure of the fact that it happens with most cars. (I like to thing that VW did not design in the lower left windshield corner leak, the rust holes in the floors and all the little rattles and squeaks as well, but sometimes I wonder about that.)

My current car is the first mark II I have owned that didn't have this issue. Then again it came with completely hacked up foreward harnesses which I had to rebuild, so every electrical connection was cleaned and coated with dielectric grease and every wire which was sketchy in any way was repalced (1" twist, soldered well/ saturated, and covered with a thing coat of 'liquid electrical tape' and then as the liquid vinyl was setting up, heat shink was slid over the top of it and heated from the center out, forcing the semi-set up liqid vinyl out the ends - (best wire splice I know how to make)

Will also second, if you don't blip the throttle at start up if the battery light comes on that it is only a matter of time before the car dies due ot lack of charge in the battery.

Will also second that supplying B+ with a diode (with or without a fuse and relay) will make the charging system come on and stay on without having to blip the throttle, SO LONG AS the electrical connections are clean, solid and not adding resistence to the power flow.

As for "residual electricy" in an electrical component..... Can an electric device hold a residual static charge for a while? Yes. Is the charge significant and reliable? Not often. Then again a cathode ray tube can hold enough static charge to really mess you up after a week of being unplugged, but that is a rare exception.

Carbs or no carbs.... if you are not getting 12 clean volts with a diode to the blue exciter wire post on the alt, your battery light will come on at start up.

Don't claim to know all the fine points and details as to why, but I do have a lot of first hand expereince with mark II's needing a throttle blip at start up to get the battery light to go off, and how to circumvent that situation.

I think this thread is mostly an argument about theory vs real-world-fuctionability.


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## WaterWheels (Aug 14, 2005)

>>antichristonwheels


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## WaterWheels (Aug 14, 2005)

>>Seax_Smith


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## WaterWheels (Aug 14, 2005)

Sorry for this being late and not part of the above, but I forgot so here it is . . .



antichristonwheels said:


> . . . I don't know where the carbs and strom comment came from.


if you are asking that as why did I add somthing about it to my post, then I can only state that you brought it up.



antichristonwheels said:


> Connect a wire from the 12V at the coil to the exciter without a diode. If you have a carb and mechanical pump the engine will not turn off...


If you are asking yourself in a round about way why you brought it up or what caused you to make the statement, you will have to answer that on your own.


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## antichristonwheels (Jun 14, 2001)

There is no "residual electricity" total BS, shows your real ignorance about electronics. What you think the blue wire is like a battery? Magic electrons are there just waiting? Again if your are correct, go ahead and pull that blue wire and let us know how it goes. These are not self exciting alternators. It will not work. blipping the throttle is required because the delta is not enough to induce enough current to get the alternator "on" at idle speed. This show your real ignorance about the alternators in our cars.

"Of course this is guess work on my part and my understand of the way it should work." This means you are really talking out your backside. I have run cars like this for years. you don't know how it works so this might be a good time to shut up.


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## WaterWheels (Aug 14, 2005)

I don’t know what your problem is or just why you are having a such a tissy fit like some 10 year old, but OK, I’m game. Have you Googled the phrase “residual electricity” like I suggested? Somehow I think you did not or that asinine statement above would never have been written, “There is no "residual electricity" total BS”. If and when you do make an Internet search on that phrase, you will not only have all those millions of web sites to read through but can also contact each and every person who wrote or posted information or comments about it letters telling them they are full of crap. My commenting about residual electricity does not show ignorance on my part, it shows that I do read up on things in an attempt to understand them. You on the other hand don’t seem to do that kind of dificult and tedious work which leaves you on the in the dark, so just who is the ignorant one?

What is this constant “pull the blue wire” rant? I am fully aware that these alternators are not self exciting, that is why there is an “exciter wire”, duh. I am also aware that due to age and neglect on the part of owners it is sometime necessary to raise the engine speed to make the alternator start the charging process. But un-like yourself it seems, I know how the system is “supposed” to work and “blipping” the throttle is not written in the owners manual anywhere to be found. I would even go so far as to challenge you, that right a challenge, to find and report back one article, manual, repair book, instructions or whatever that says it is “required” to do that when you start the engine. Then we can all determine just who is being ignorant and who is not. Up for the challenge?

Have you ever heard the phrase, “taken out of context”? It is what people do, like reporters or people trying to save face or detract from the truth, to boost their agenda by using a small part of what someone said to paint a totally different picture of some kind often in their favour. My saying that something was a guess on my part was said while talking about a particular area. Now if you want to go back and discuss that area and what I said, fine, we can do that. But for you to convert one commenet in one area to a general overall statement of things again does not show “my” ignorance or talking out “my” backside, but how about you and yours?

I’m sorry if I hurt your feelings, really. I’m sorry if you just don’t know how to crawl out from under this rock you placed yourself under, again, really. But if you want to act like the superior being then you need to come up with something that rings superior, not these childish rantings and temper tantrums. I challanged you on one (1) thing, although more could have been done, and it still stands. Now show me just how wrong I am and if you can’t then maybe someone else should shut up, no?


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## antichristonwheels (Jun 14, 2001)

I was just trying to help the op out with valid answers. I don't need to type a bunch of BS to satisfy my ego.

try this:


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## RyanBabros (Jul 2, 2010)

Hahahahaha! Wow! I fixed my charging problem, but I see some problems never go away. Haha. :beer:


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## WaterWheels (Aug 14, 2005)

antichristonwheels said:


> I was just trying to help the op out with valid answers. I don't need to type a bunch of BS to satisfy my ego.
> 
> try this:


More or less exactly what I expected. Thanks for not disapointing me :wave:


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## jorge r (Apr 27, 2006)

RyanBabros said:


> Hahahahaha! Wow! I fixed my charging problem, but I see some problems never go away. Haha. :beer:


:thumbup::beer: I'll drink to that!
The alternator's blue wire terminal grounds the line so the dummie lamp lights up in the dash, once the alternator is chargning, the blue wire is not grounded anymore, it becomes positive. Having two positives on each side of the dummie lamp in the dash will not cause the lamp to light up. 
I wouldnt ground or put +12 volts directly on the alternator's blue wire terminal unless there is a lamp in the jumper line and only connect to +12v.


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## mk4boost (Jul 31, 2010)

hoping to bring back an old thread... 84' 1.6L diesel, same issue... 

I tracked the exciter wire into the dash, it runs into a relay that I found near the glow plug relay... the relay itself is corroded and rusted... anyone know what relay that is? I think that's what's causing no signal to the alternator


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## j2crawford (Feb 18, 2016)

*battery no charging/ not battery light on start up*

I have a MKIV and I have the same problem. I see what the problem is, the exciter circuit is not working. I cannot find how to fix it. I check the blue wire under the battery and it seems fine, I replaced the fuse box, I replaced the alternator, I replaced the battery.... how do I fix this?


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## Mr.loops (May 27, 2010)

j2crawford said:


> I have a MKIV and I have the same problem. I see what the problem is, the exciter circuit is not working. I cannot find how to fix it. I check the blue wire under the battery and* it seems fine*, I replaced the fuse box, I replaced the alternator, I replaced the battery.... how do I fix this?


Was this a visual check or did you use a DVOM?


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## InlinePerformance (Oct 25, 2008)

I can say this-their is a lot of actual useful information here and some nit picking as well......with that aside i myself ran my rabbit with aba swap for close to 6 years with the alt exciter wire hot (12v) key on and it charged fine, never burned up any alternators and never ran after killing the ignition (turning key off). Their was no diodes, no resistor, no bulb. As long as the excitor received 12v my alt began charging. On cars previous to this ie mkii's and mki's that were stock and had epic cluster working disasters i did the same-never had problems on these either. My teaching said yes-a bulb and or diode is recommended for excitor circuit for load AND current back feed safety but when push come to shove its really only their to keep the alt "active" ie regulator "turned on" -put in simple words. So no,12v to the excitor in my experience would not damage an alternator. And as far as low rpm/reving to get the alt charging is not unusual as well its old technology.....its not that great and every alt has a min rpm and some of these cars just idle very low after 30 years of running . I worked at advance auto as a kid- cheap remans are just that-cheap 


Sent from my iPhone using Tapatalk


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## j2crawford (Feb 18, 2016)

*blue wire*

I am getting 5 volts at the exciter wire and 12 volts going into the cluster. the 5 volts is not getting the alternator going. I cant find and breaks or reasons for the exciter not producing 12.


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## InlinePerformance (Oct 25, 2008)

Bad connection or just bad cluster. A bad connection can cause a voltage drop.


Sent from my iPhone using Tapatalk


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## Seax_Smith (Jun 1, 2007)

Just went threw a round of this today....Long story but I ended up having to swap in a low amp 8 valve alt that had been sitting around for way too long.

Got the alt installed and driven. Went to check to see if it worked. battery light stayed on in the cluster and +B was 12.4 volts. Car was fine before the swap. Cleaned up the male connector on the alt and jumped +B to it directly fron the lug on the alt. Battery light went out and I had 14.4 volts across the battery (HUCO brush pack). Put a new connector on the blue wire while I was trying to think of a solution and trying to remeber what I did with the new wire I ran 5 or 6 years ago. Took the jumper off, plugged the new connector restarted the car and still had 14.4 at the battery ..... 
Connector looked fine to me. only reason I replaced it was that it gave me something to do while I thought about where to start trouble shooting.

Thing that makes me happy is the battery light still goes off by itself without a throttle blip.


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## epic designs (Feb 4, 2004)

I kind of like the throttle blip thing. 

During harder cold starts it reduces the load on the engine. After it warms up a bit I can give it a blip and the rpm drops a couple hundred rpm as it starts charging. 

All my vws have always done this. Are they not supposed to?


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## Seax_Smith (Jun 1, 2007)

epic designs said:


> I kind of like the throttle blip thing.
> 
> During harder cold starts it reduces the load on the engine. After it warms up a bit I can give it a blip and the rpm drops a couple hundred rpm as it starts charging.
> 
> All my vws have always done this. Are they not supposed to?


They didn't come out of the factory needing a throttle blip the get the alt excited and charging.

It is about as common as "I filled up the tank and drove 300 something miles and now I need to fill up again"

Generally speaking, it is caused my pristinenessly-challenged grounds and/or resistance in the wiring. Sometimes it is the exciter stuff inside the alt. Rarely is it ever first on issues to address for most people.


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## vwbobby (Apr 5, 2009)

Seax_Smith said:


> Worked in Parts for a lot of years.... junk remans (starters, alts, etc.) are sort of common depending on the reman company. [the really cheap remans come form palces which gut the core, slpa in new intrenals and ship them out WITHOUT checking anything].
> 
> so you will be charging as normal OR use the 10 v you are getting out of your blue exciter wire (10 v should be enough to trip most relays)
> Control ground = body ground anywhere
> ...


_____ME: You probably need regulator part number 1 197 311 022, EL 14V 4C OR on eBay or Amazon Transpo part number IB354. They are $55-65 at Autozone and $14-18 online. This part is a generic German part used on Mercedes, BMW and let's see, uh... VW
_____ME: This is what I'm starting to do anytime I work on a VW. I make 2 ground wires with 10G wire. Ground (extra wire) the negative on the battery to the fender well - Don't use the top bolt near the fender joint due to rain, etc. Then with the other 10G wire I ground the engine (maybe valve cover bolt) to the fire wall. Then I get a black battery cable and ground the engine block to the frame. There is a metric allen bolt just below the (top) alternators that should work on the block ground. This procedure should be step #1 before you do anything else. Hope this helps.


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## chickenfriend (Jan 31, 2005)

epic designs said:


> I kind of like the throttle blip thing.
> 
> During harder cold starts it reduces the load on the engine. After it warms up a bit I can give it a blip and the rpm drops a couple hundred rpm as it starts charging.
> 
> All my vws have always done this. Are they not supposed to?


You might have a poor blue wire connection or the blue wire itself is frayed at the connector to the alternator.

Why the revving might help could be due to residual magnetism on the alternator rotor--revving the alternator would boost the ability of that to excite the alternator, on top of whatever the blue wire is bringing in (which might not be much at all).

Also consider that during starting, the battery voltage will dip and then recover. The recovery in system voltage might be enough to finally get current to the exciter circuit in the alternator.


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