EDIT: Amp test is showing 0.6 not being connected to Alt, jumps to 0.72 when i connect the Alt. (disconnect Neg lead from battery. VOM set to 10A terminal 200ma setting. One lead from Vom to battery Neg other to Neg lead.)



Hi folks I bought a bit of a monster here. Had it 3 weeks and it's had a problem every day since.

Most recently I left the rear doors open for a few hours and drained the battery. It was turning but not firing. I have another thread relating to this but it was a fuel leak that is now sorted.

Anyway, I only had a 50ah charger, so put the battery on for a couple hours then it fired up again. Took it for a run and parked it. Went to start the next day and it turned slowly but wouldn't fire.

I bought a Multimeter and checked the battery. It was showing around 12v, so i took it off and charged it over night. Bearing in mind my battery is 70ah, my little trusty 50ah charged it fully. I put my VOM on it and it was showing 13.2v. I put it back on the van and boom. Started Fast and Furious. I thought I'd sorted it.

Next morning I went out and before anything I checked the battery on the van. 12.1v. disappointed I turned the key. It started right away but I knew the drop in voltage wasn't a good sign. The van had previously been stood so I figued the battery was simply knackered as it wasn't holding a charge, so i went straight out and bought a new one.

Here's where it gets comlicated;for me anyway.

The old battery has been in the garden holding afull charge of 12.7v for 3 days!
The new battery keep dropping to 12.4 over night.



Here's what I know now.


VOM showing 13-14v while running telling me it's charging. Turn it off and the battery is showing 13+ volts, but then it visually drops in V's as the seconds pass.

If I remove the negative lead, the V's return to normal or at least stop dropping. Connect the Negative and it starts dropping again. (OK so this is a Positive Parasitic Draw)

Removed the aftermarket stereo, but no change. it still drops.

I don't know how this van should be wired, but there is a negative lead from teh battery to the starter. I'm assuming it's a ground? Held to the bottom of the starter by a small nut.
The positive lead comes from the battery to the starter first then on to the Alternator. Assuming this is normal? I have checked using my VOM that the Diodes are ok; i think. I set my VOM to Diode, touched the Positive on the Alt and touched the casing with the negative terminal. No reading. swapped the red and black and reading around 550.


This is a simply van. No remote locking, interior lights off, doors shut.

If i connect only the starter, the VOM shows no drain. Only when I connect the Alt does the V's drop. All of these testes on Start and Alt were with engine off.


I'm a bit stuck.~



Only other thing i could add is that the single wire from the alternator that I've assumed it for the Bash light for the battery, was recently snapped. I've reattached it.

Hi Barascudo

I am a bit unsure of your parasitic drain current measurement. If your meter is set to the 200 mA current range, a reading of 0.6 means 0.6 mA i.e. negligible. On the other hand, if you are on the 2 A range a reading of 0.6 means 0.6 A which is rather more than I would expect. Can you clarify what you are seeing ? A typical parasitic drain would be 100 mA which would flatten a fully charged 100Ah battery in very roughly 1000 Hours, so we are talking 6 weeks, not overnight.

Be aware that the background drain in modern vehicles may take a while to settle to its lowest figure, as different systems shut down progressively at different times after you have removed the key. I'd suggest checking it for 5 or 10 minutes to see if things change (you might need crocodile clips to avoid arm ache !)


A batttery under alternator charge should show about 14.5 volts, 14.0 is a bit on the low side to give a full charge. Once charging stops, the voltage will immediately drop to something like 13.5 volts, then more gradually decrease to something like 12.5 volts. This is normal behaviour.

If the battery is OK but starting is sluggish, the first thing to check is the whole of the earth return cable from starter to battery. If your van is the type that has a teed-off connection lug to the vehicle body part-way along this cable, check that carefully too.

Hi Barascudo,

Like Anthony489, I am puzzled by your reading your multimeter. I have access to two multimeters with 10A internal shunts, both meters have a switch selectable 10A range to use in conjunction with the dedicated 10A socket.

You mention a broken small single wire from the alternator. This will be the D+ connection, this connection does connect to the battery warning light on the dash, but as well as the warning function it has an important second purpose. With the ignition ON, a small current flows through the warning bulb, and the alternator field circuit. This current helps the alternator to start generating, and without that help the alternator may not start generating. You would then be running on the battery only.

Given the manufacturing year, 2005, your vehicle will be an x244 model, similar to my 2.8 JTD. eLearn shows the same wiring diagram for "Starting and Recharging" for both the 2.0 JTD, and the 2.8 JTD. From this I am puzzled by you description of the alternator being connected via the starter motor. eLearn shows a dedicated alternator fuse at the battery positive pole. eLearn diagram E5010 attached.


The battery negative or earth cable on my x244 drops from the battery terminal to a flag terminal on the RH inner wing, just in front of the RH engine mounting. The same cable continues at the bottom of the intercooler and radiator, before terminating on an extended 8mm starter stud (RHS of third photo). Your description of a small screw on the starter motor seems different.

Thank you both for replying. I'll reply in kind in order.

OK, so while I'm a keen DIY'er I've little to no knowledge re Miltimeters or Electricity. it's on my list.

Let me try again with less words.


I was initally reading 0.72 when set to 10A.

This has somehow settles to 0.350-60

I mistkenly had my inital Multi setting to the 10A socket but turned it to 200ma. I don't know how that multi works but I have another where it'a Automatic.

This is for sure.

Charing current or Volts (I don't know) while running is over 14. the battery after engine off is above 13v. If I remove Neg lead from battery, Volts slowly drops to nominal levels. i/e 12.6 If I leave it on over night it'll drop to around 12.4

In real time If I disconnect the neg lead from battery the voltage will stop dropping and even rise. Good battery, Brand New. Cells working.

For all intents and purpose, the Alt is working. It charges and the Battery light goes out. Engine off all doors closed, radio disconnected. Neg lead off battery and Multi set to 10A with red lead in 10A socket. Red lead to Neg lead. Ned or Com lead to battery. 0.350............If I remove the Alt from the Starter motor it's drops to 0.02 which I would assume is normal.

So, I've done a Diot Test while on the vehicle. Removed the red lead from Starter to Alt. Put multi in Diote Test. Reading 550 one way, then reverse cables and no reading. This is supposed to suggest the Diodes are good?

So to clarify.

I have a draw on my battery that goes away if I disconnect my Alternator. However the Alt is charging as it should and the batteries are both Good. I've had the van 4 weeks. If i don't use it for 2 days it will turn over but not start. Last Low reading was 12.1 but it still started.


Can I have a positive result from the Alternator Diode Test on the vehicle and it still draw volts from battery?



Communicator' something is seriously wrong or changed for the worse with how my van is set up. I'll add pics tomorrow for clarity, but I'll expalin here now.


My Neg lead has 2 wires from it. One main Black one that does indeed attach to the inner wing. It appears solid but the van is rusty. However on the surface it looks good.. On the same neg lead from the battery is another, but it's RED! This wanders across the engine bay and down to the starter Motor base and it attached by a small nut. I removed it and it has a very long thin threaded bolt that appears to run the length of the starter.

Chasing from the Positive lead from teh batter it meanders under the radiator then up to the starter. One thick red cable. Another reed cable runs from the alt to the starter, completing the connection.

My finger is pointing the the Red Neg lead from battery neg.

Sorry finger missing from image.

The pic with the starter showing the black lead (which is red internally) attaching to bottom of starter.

Jeeeez the more I look at the pics the more i realise what a state this poor thing is in!.

Apologies for Typo's I can actually spell very well

Hi again Barascudo

This is a quick reply as I am busy hedge cutting today. I will look at your pics in more detail later.

From your description, the parasitic drain on the battery is a good fraction of an amp, which is much more than I would expect. If you think of voltage as like water pressure and current (Amps) as like water flow (gallons per minute) it might help visualise things.

It would seem that your van has been rewired in a rather shoddy fashion. This may have been an attempt to circumvent a problem rather than diagnose and fix it properly. In view of the visible surface corrosion, I would be deeply suspicious that one or more electrical connections are also internally corroded, especially the earths.

I'd recommend tackling the wiring first, by replacing/cleaning wires and connectors so as to put it back to standard spec. Then you can chase the parasitic drain, if it's still there.

Anthony489 said:

Hi again Barascudo

This is a quick reply as I am busy hedge cutting today. I will look at your pics in more detail later.

From your description, the parasitic drain on the battery is a good fraction of an amp, which is much more than I would expect. If you think of voltage as like water pressure and current (Amps) as like water flow (gallons per minute) it might help visualise things.

It would seem that your van has been rewired in a rather shoddy fashion. This may have been an attempt to circumvent a problem rather than diagnose and fix it properly. In view of the visible surface corrosion, I would be deeply suspicious that one or more electrical connections are also internally corroded, especially the earths.

I'd recommend tackling the wiring first, by replacing/cleaning wires and connectors so as to put it back to standard spec. Then you can chase the parasitic drain, if it's still there.

Click to expand...

Hmmm, so I am not the only person to be involved in hedge cutting. I also have trees to contend with. While I have being attending to this and getting my PVC back on the road, Mr Mole has taken over the front lawn. Will be away for two days, first trip in nearly 3 years. May not be online.

BaraScudo,

Your red negative lead is in effect the return lead for the starter motor current, which current, while of short duration is by far the highest current in any part of the vehicle electrics. The same wire is also the engine block earth, and as such is part of the connection between the alternator and the battery. A poor connection here will have a bad effect on battery charging.

The long bolt used to connect to the starter motor is one of the carcase bolts, which hold the starter motor together.

Yes I think that's a good idea.

But would a bad ground create a parasitic draw from the alternator only?

The system works. It starts, It charges, it runs daily. I don't have any flickering lights or radio problems. It literally only occurs when I connect the alternator to the starter.

Communicator said:

Hmmm, so I am not the only person to be involved in hedge cutting. I also have trees to contend with. While I have being attending to this and getting my PVC back on the road, Mr Mole has taken over the front lawn. Will be away for two days, first trip in nearly 3 years. May not be online.

BaraScudo,

Your red negative lead is in effect the return lead for the starter motor current, which current, while of short duration is by far the highest current in any part of the vehicle electrics. The same wire is also the engine block earth, and as such is part of the connection between the alternator and the battery. A poor connection here will have a bad effect on battery charging.

The long bolt used to connect to the starter motor is one of the carcase bolts, which hold the starter motor together.

Click to expand...

I see so although it may not be to spec the circuit is probably ffine?

It must be. It's charging. The battery dies charge. It'll charge to over 13v then if I remove the neg lead it will hold its charge indefinitely it seems.


The only thing left for me to know or check is if I can still get a good Diode test result but have one failing diode causing a drain.?

That fact there are no other wires or connections visible to the alternator is starting to look like a case closed conclusion.

With no engine running and nothing turned on it only drops when I connect the circuit to the Alt. So it must be the Alt?? ??

Well I'll be damned.......

Come out this morning and done the Amp draw test. It's now showing .005..........

I'm baffled.

Nope false alarm folks

I disconnected the Alt last night so the reading was low for that reason.

I've just done a 50 mile trip with no issues. Stopped and resting battery voltage is 13.2 I'm going to leave it for now. Maybe I'll take a close look at the ground points instead.

An update folks.

Turns out there must have been a bad ground issue in the past. The Earth on the right side under or near the airfilter housing was almost hanging off. I'm going to assume the way it was was a work around to the ground issue. Looks this this was the main engine ground. Anyway, I've fixed that ground issue and connected the alt directly to the battery and not the starter. Everything is working but I still have a parasitic draw of around 450ma. I'm saying 450ma as I have it on 10A and it's showing 0.450.


So, I have done a Diode test. Diode setting on Multi m touch B post and alt casing. Only 450 this time one way but nothing when reversed.


So, here's my final question (i hope)

Parasitic draw from Alt. Can a positive Diode Test using MultiM still mean I have at aleast one diode failed and creating a draw?

Charging volts are 14.5 even with lights blower and radio on. Battery is charging. Battery holds it's charge if i remove Alt.

I can't find a single video that tells me otherwise. Every single reference is saying that if it's charging, it's Good. If the Diode Test is a pass then they're good too.

I'm starting to think every video on YT is copying from the one before.


An alternator MUST BE ABLE to work even with only one diode gone and still create a draw issue.


OR is it the regulator?


Come on people. Must be a genious or two in here.

BaraScudo said:

=======================================================

I have checked using my VOM that the Diodes are ok; i think. I set my VOM to Diode, touched the Positive on the Alt and touched the casing with the negative terminal. No reading. swapped the red and black and reading around 550.
=======================================================

Click to expand...

Hi,
Having read the above section of post #1 in this thread, I think that you may not be interpreting your results correctly. Normal silicon diodes have a forward voltage drop of about 0.55V, and even more efficient types have a drop of about 0.45V.

When applying the diode test as you describe above, you are effecively looking at two groups of three diodes in series. This means that with the negative lead of the multimeter connected to B+, and the positive lead connected to chassis, you should not read less the 0.9V, and more probably about 1.10V. You are not seeing this. Also when connected with the positive lead to B+, you should read OL for overload, or 3V, which is typically, the maximum voltage used on the diode test range of a multimeter. You should not get a zero reading, except for a short circuit. One interpretation of your results is that one of the diodes has failed, but is not a full short circuit.

As an aid to understanding, I have modified eLearn diagram E5010 by adding some annotations to the alternator, in particular 3 off letter"o" at the points where the diode packs, and the windings are connected together.

To further diagnose your fault, I suggest using a small 12V test lamp or bulb, between the battery +ve pole and the alternator B+. The bulb should not illuminate. Also note that the current ranges of most multimeters add a small, but significant resistance into the circuit. This could result in a false low reading. The true current could be greater than that which you are reading on your meter.

I am sorry if the above confirms your fears, and threatens your wallet.


Do please take care when working around batteries. They store a lot of energy.

I've Been following this thread with interest but can't add to the excellent technical knowledge of other contributors but do recollect an occasion when I had a battery discharging overnight for no obvious reason. I had (and still don't!) no knowledge of diodes and such but changed the alternator on a hunch (and a prayer) which cured the issue.

Much more recently I fitted a double din Chinese-branded sat-nav unit into my van only to find that it's constant ambient current draw was nearly 1 amp! This might be ok for a vehicle that is used daily but not for a motorhome which might be parked up for a couple of months.

Thanks for stepping in once again guys I really appreciate it.

As I've gone on it's becoming clear it is the Alternator after all. It has to be right? It only drains when it's connected!


I'm disappointed in my decision to buy this. I've never bought a vehicle in such bad shape, but I do enjoy fixing old motors with new parts and giving them a new lease of life, but with the amount of rust on this old girl, it's becoming a futile endeavor.

I paid £1000 for it over a month ago and so far it've spent £320 on welding (but it needs more) 30 or new rear lock, 30 on caliper piston kit, 30 on o-ring kit for fuel pump leak 20 on power steering fluid to flush it. It keeps going up. I've just ordered two roll bar drop link as N/S has snapped. Now it needs an Alternator and a Clutch soon.

Not sure she'll see another month with me at this rate. If it wasn't for the rust I'd fix her up no problem.


Anyway, off on a Tangent there. Thanks for the PDF and the earlier pics you sent Communicatator. It highlighted the state of mine. The cabin is near mint but it seems the underside etc has been neglected. The fuel filter was jet black. It's all serviced now. I'll sort the drop links and put it up for sale i think before it becomes a money pit. Alternator is only an issue if it's not used for 3 days. I can get a new one of Ebay for less than £100, but I can only anticipate the suspension parts failing in sequence too then the clutch becoming a problem.


As for the readings I posted my Bad. I'd assumed it would be interpreted as 0.450 or 0.550v when set to Diode test. With this said, Neg black VOM to B-Post and Red lead to Casing it's showing 0.450v

Swapping it's started at 0.350v and it keeps rising to over 0.800v. I never had a reading last week the other way. Maybe swapping earth and connecting direct to battery has worsened it or clearly defined the problem? I don't know. I just know I tested it many times and only had a reading one way.

Addage to last post:

I kept the connector on the alternator for the diode test and it went from 350 to 900+ then zeroed and stopped. Turned the VOM off and did it again and it repeated. Not sure how to interpret these readings.

I think I'm going to assume Alt needs replacing?

All in agreement?

If you are trying to perform a diode test with the battery connected to the alternator, you will not obtain sensible results.

Before embarking on the work and expenditure involved, have you considered the simple test lamp check?

This test could be performed using a traditional metal filament, metal capped, warning or sidelight bulb.

Hi, Communicator, no i have not ried the lamp test yet as as come to no other conclusion.

The battery drains when I connect the Alternator. There are no other wires of connections involved.

If the battery drain when I connect the Positive to b-post, then my Alternator is draining my battery. It stops when i disconnect it.

I've always know this was the case, but according to many many video's on YT for instance, a diode test can confirm this and initially the Diode Test appeared to prove it was OK.

My latest readings using Diode Test aare as above. 0.450v one way and 0.350 up to 0.999 then resets to zero the other.

What I'm really asking is can there be something else draining the battery when I connect the alternator if nothing else is connected to the alternator? What I'd also like confirmed is the valdity of the Diode test purported by so many videos on the Internet.

Occams razor. All points to Alt failing.