No excitement anymore

[Smcknighty]

My blue exciter doesn't get me going anymore..

Now I've made my attempt to get into the innuendo thread.. I'm only seeing 4v from the business end of the blue exciter and 12v on the battery. If I put a 12v feed to the blue exciter I get an alternator charge 13.9 or so and all is good. (Engine suddenly under full alt load etc)

So from this test I conclude the alt works but that the blue exciter is no longer exciting enough at 4v - is this just a natural ageing thing? Should I be getting some Viagra shaped battery's and adding them in line to give him a pep?

I've replaced the alt brushes and volt regulator fairly recently, not keen to do it again unless this def points at that. The red light of no charge is on.

Only linked factor is I've just started trying to sort out the split charge relay which was pretty messed up - the blue exciter is of course present here.. I fully admit the electrical stuff is a challenge to me..

[Smcknighty]

12v at the blue exciter when ignition is on but van not going 4v when its going

Red light stays on

[Oldiebut goodie]

Remove the exciter connection to the split charge relay - it may well be interfering with the alternator excitement. Then check that the alternator is charging as it should. If it is redo the split charging system from scratch and use a voltage sensitive relay instead.
Interfering and excitement in one sentence!

[Smcknighty]

And when I split the exciter the red light goes out

I'm starting to think I've somehow broken this with my work on the split relay - but how I don't know

[Smcknighty]

Sorry obg didn't see that - I will pull all the split relay wiring out of the equation

[Smcknighty]

Pulled all the wiring - no difference. I get 12 v when the blue is not connected to the alt at idle , 1.5v when it is. When I give a constant 12v it charges - hmm is the conclusion that the voltage regulator has barely made it nine months?

[Smcknighty]

I'm reading this

http://www.pelicanparts.com/techarticle ... eshoot.htm" onclick="window.open(this.href);return false;


I've got to this part having passed the first test I think


To check the D+ portion of the system, it is necessary to find out if the D+ output can produce enough current to drive the alternator to full output. To do this, short the D+ and DF terminals on the relay board. This will provide the maximum field current to the alternator that the alternator ITSELF can supply (not the battery, as in the earlier check) and so checks the remainder of the circuitry. If this test puts the light out, then the alternator is good, and the trouble is elsewhere. If it doesn't, then the alternator is almost certainly bad, with one other possibility:


Anyone any idea how/ where I can do that test??

[Oldiebut goodie]

Rev it up above idle and see if it charges - a lot of alternators don't charge at tickover. I know mine doesn't nor does mine in my boat - I have to give them both a bit of throttle to get them charging. Several other people have this also.

[Smcknighty]

Yeah it used to need a blip after starting to get the light to go off. No joy now though even if I give it some beans for a while. I've swapped the voltage reg as it was only a tenner, didn't make any odds, I'm now thinking its just a dead alternator. At least it didn't happen in France..

[Oldiebut goodie]

Have you tried putting 12v direct to the blue wire or alternator terminal from the battery to see if that works?

[Smcknighty]

Yeah - so if I put 12v from the battery direct to the blue I get an immediate rise in output to standard alt output e.g. 13v. But if I take it away again it goes. I read this to mean that the alternator isn't kicking out enough charge to sustain its self - from what ive read i thought it takes the blue exciter charge to get going but should then sustain itself (hence volts go back up and light goes off?)

This is completely not my area though..

[Smcknighty]

The below sounds exactly the same as me

Vw heritage don't have an alternator till mid week anyways. I have tools and a burning urge to break stuff, what's the worst that can happen?


Fireman Comments: Hi great read and very useful. I have a VW transporter that gives battery voltage to the D+ wire until you connect it then its 1.6v regardless of engine running or not. Light stays on and no charge. Make up a wire direct from battery + with an inline bulb and this extinguishes when the engine starts and new alternator charges fine?
February 3, 2011
Followup from the Pelican Staff: I'm not a super alternator expert, but I believe that you will see this behavior when the diodes in the alternator fail. The light will sometimes stay on all the time, and you may even run your battery down from the light being on all the time. The solution is to replace the three or so diodes in your alternator - I think that will fix your issue. - Wayne at Pelican Parts

[Smcknighty]

Am staring blankly at the alternator.. - I know, I'll chuck it back in, go for a run n hope higher revs sorts it

[Smcknighty]

So I put it back in, went for a run all the way to vw heritage.. Still didn't magically fix itself. The alt I have was on speshul order but I looked at the 86 on alt and it was the same just with bolt on connectors. So now have this fitted. For a minute I thought my foolish spend didn't work as the light stayed on but blip of the throttle and I was off.

Vw heritage kindly threw in a push start (rofl!) - don't think they expected that - above and beyond!