Alternator exciter connection

RobWid

RobWid

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Hi

Just had to stop off in my travels to get a new alternator fitted. Overall great service and now back in the road.

But ... they didn’t reconnect the exciter cable which activates the relay - so no charge to my leisure battery and I’m now a long long way away from the garage.

So question 1 - is it obvious where to connect the blue cable to? I believe it’s the D+ but just wary of putting it somewhere it doesn’t belong!

Question 2 - The présent cable simply has a crocodile clip on the end! Seems to have worked fine for 18 months of ownership but is it possible to buy the correct connector and what am I actually looking for?

(Vehicle is 2003 2.2HDi AutoSleeper Symbol)
 
As a temporary measure clip it to the battery positive terminal.
At least that will get the split charge working but don't forget to unclip it when you stop.

Depends on the alternator but it may have a heavy wire and a much smaller wire, both on studs with nuts.(most likely if there's a Croc clip) Connect to the smaller terminal.
If its a smart alternator it will probably have a few wires and plug in connectors so the above won't work.
 
If it has a crocodile clip on the end then I guess it was clipped to the terminal at the back of the alternator, that is at the opposite end of the alternator form the drive belt.. This will have a fairly heavy lead already fitted to it and the terminal should be around 6mm or so in diameter. This should get you going for now.

The cable with the clip should be about the right length to reach to this point. If it doesn't, don't force it as it must have been attached somewhere else! There may be a terminal under a cover on the alternator which only becomes live when the alternator is running. A voltmeter will help you identify this.
 
DBK said:
This will have a fairly heavy lead already fitted to it and the terminal should be around 6mm or so in diameter. This should get you going for now.
Click to expand...
That's the battery feed wire and permenantly live.
It should be to the thin wire... Ign switched field wire.... D+
 
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pappajohn said:
That's the battery feed wire and permenantly live.
It should be to the thin wire... Ign switched field wire.... D+
Click to expand...
Yes, you're right of course. :) It's the crocodile clip which is weird.

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Thanks for all the suggestions - I must admit to being surprised about the crocodile clip and yes it is the (very) thin blue wire I was referring to.

Will crawl down under once I find a clean safe space to work in the next day or so. My initial look on the roadside didn’t feel the best idea!

thanks
 
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Reactions: DBK
Hi still struggling with this ? even after a cold morning under the van.

As mentioned new alternator fitted - thin blue wire not reconnected by garage - a long way a way from where I am now so can’t go back. Alternator seems to work fine and charges Vehicle battery fine.

There is a D+ post but checking this with a volt meter I simply get a slight negative voltage - a few milliamps.

Mu solar set up is working fine On the leisure battery for the mo but want to get everything set up as it should be again.

Can’t remove the plastic cover over the back of the alternator due to the proximity to the oil filter.

Reading up on this then many people say an alternator won’t work without a D+ connection? Doesn’t seem true for mine!

Have tried connecting to vehicle battery to trigger the relay and works well but only ok for a temporary solution.

So ...

(1) Any ideas as to why no voltage from the D+ terminal - am I missing something daft?

(2) Would it be easier to simply fit a voltage sensing relay which avoids the need for the alternator link?

Thanks in advance - Rob
 
did you have the engine running when testing for voltage from D+ terminal
 
I wonder if the garage fitted a "Single Wire Alternator" for ease ? We looked a fitting one on our Unimog when that was playing up. on
Plenty of info and pictures online about installing them, maybe you could get some ideas from them ?

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Hi Thanks - Yes and nothing at all directly off the alternator. Will explore again tomorrow.

Will take a look at ‘single wire’ alternators - again thanks.

Decided I am probably going to remove the oil filter which is presently blocking access to the rear of the alternator so I can see what’s where more clearly.

Thanks again for all the suggestions.

Rob
 
Not very well up on alternators but the D+ is ignition triggered and lights the ign warning light.
Once the alternator begins charging the warning light goes out, meaning there is no voltage, the warning light goes out and the alternator is then self exciting.
Try connecting the blue wire to D+ and see what it does then with the engine running using your meter on the HAB BATTERY.
Nothing to lose by trying.
 
Ok thinking again ...

Guessing that Jockaneezer is right in that it’s a single wire alternator - based on the fact that it only has a single wire and works - ie doesn’t need that wire connecting for the vehicle to start, run and charge! (Will crawl under tomorrow and try and see a label to get to some info to confirm.)

However would be great to be able to use the alternator to charge the leisure battery when driving.

So it seems there are two choices, fitting a voltage sensing relay (more cost) or tapping into an ignition switched cable to activate the existing relay (zero cost?).

It’s only a trigger voltage and very light cable so assume no real issues about perhaps connecting into the feed for the driving lights which come on with the ignition?

Any other suggestions of convenient and perhaps better places?

Rob
 
Pappajohn - yes the rear of the alternator is virtually inaccessible unless you perhaps remove the oil filter which was going to be my next step but ...

Having tested the post marked D+ and it’s dead and connected the wire up to see what happens and nothing at all. Wondering if with the single wire alternator (assuming it is) this is just legacy markings on the case and effectively meaningless on this device?

So since the alternator seems fine from the vehicle perspective now looking for an easy way to simply trigger the relay on start up for the leisure battery - see above post.
 
Can you find the wire which originally connected to the D+ post.
If so connect the blue wire to that, its ign switched and now redundant.

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Hi The only blue wire I can see is the one that was connected to the old alternator and that ran directly (unfused) to the relay. But thanks will explore tomorrow and am getting there - at least in understanding!

rob
 
pappajohn said:
Not very well up on alternators but the D+ is ignition triggered and lights the ign warning light.
Once the alternator begins charging the warning light goes out, meaning there is no voltage, the warning light goes out and the alternator is then self exciting.
Click to expand...

Not quite, The small wire to the alternator acts as an "earth" for the ignition warning light which is a low wattage lamp.
When the ignition is turned on the current passes to the lamp which is earthed through alternator winding. When the alternator starts charging, the small post becomes live & the light goes out as it is now positive to both sides.

DP
 
Just read this from 12V Planet

“it is important that the relay closes only once the engine is running so that the leisure battery is not connected to the starter during engine cranking, so a switched ignition signal should not be used”.

So back to finding a D+ feed or switching over to a VSR that doesn’t require this feed.
 
Hi Fixed ????? Finally found the D+ live after removing quite a few bits. Sadly found a protective plate that needed welding but at this age no surprise!

In the process have been recommended to replace my Battey to battery cables with more substantial ones - 16mm2... a job for later.

But just to say thanks for all the the thoughts and encouragement that stopped me giving up!

Rob

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Phil - Thanks will make interesting reading - still all very puzzling at times compared to a car!
 

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