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Update

Many thanks for all the help received so far.  As promised here is an update.  I managed to burn out the earth wires to most of the instruments by accidentally touching the live ammeter terminal to earth with battery connected!  However, it encouraged me to test all other connections.

* Removed all dials from the dash, replaced all earth wiring and checked that all connections were secure.

* Instruments now have LED backlights with the exception of the ignition light which retains the original bulb.  We thought that this should be 5W but the manual states 2.2W in common with all other bulbs.

* Second new alternator installed and properly connected.  Ignition light still stubbornly refuses to go out completely and ammeter shows a slight discharge - switching on lights causes the ammeter to respond appropriately.

* I am getting good readings at all relevant points - fuse box, large terminal at alternator, exciter wire, etc.  The problem of no charge persists and everything seems to point to the alternator.  Can I really have three faulty units?  The original and two new alternators have all failed to charge the battery.  My very knowledgeable mechanic at Amrest Classics measured an output of 28 volts from the latest alternator!  Internal regulator problem?

We are now pondering our next step which will probably involve taking the alternator to a company in Milton Keynes who can test and possibly correct any faults.  At least this will eliminate the alternator as the source of the problem - or not.

Will post any further results for information.

Bob

NB  We have printed all advice given on this forum all of which makes good sense and well worth following up - thank you.

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It's very unlikely you had three duff alternators Bob, although I am a bit concerned about the test your mechanic did. It sounds as though he ran it without any connection - else the voltage wouldn't have been so high - so there is a distinct possibility he has damaged the diode stack by over-volting.  Even if it wasn't duff before, it might be now.  Alternators should not be run while disconnected as there is no reference voltage for the regulator as Nobbyc pointed out in his post. That causes the voltage to rise uncontrollably as there is no load either when disconnected.

Can you tell us what these 'good readings at all relevant points' are and what instrument you are using to take those readings? The numbers you posted before are definitely not good and pointed to a wiring problem so unless you have fixed a fault, what has changed? 

From what you have told us this all started after you changed the dash bulbs, so it would seem most likely it results from something you have done during that process.  Perhaps you haven't told us the full story?

Edited by RobH
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Rob

I've tried to be as honest as I can and have certainly not held anything back.  I am not a mechanical or electrical guru and rely very heavily on people that I pay to sort out any problems.  I am also an avid reader of this forum and value highly the advice offered in many areas.  I am quite happy to admit my shortcomings and would certainly not be afraid to report any idiotic errors that I make due to uninformed fiddling - hence the burning of earth wires that nearly sent the car up in smoke..

Having spent all day yesterday passing tools and checking lights (and watching a new screen being put in the backlight of my surrey top) I am now waiting patiently for the next report from my highly competent friend at Amrest.  I simply posted the above text in order to keep you helpful people informed of any progress (or lack of progress) made so far.  I felt it was the polite thing to do when people have taken the trouble to help..

I have told you the full story as I know it "perhaps not in the right order" but the best that I can offer.  I don't have the technical knowledge to relate all of the more intricate details but I do try.

Sorry.

Bob

 

Edited by Bobble
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Bobble,

You mentioned "all earth wiring" above, but I think about your gauges.    Have you checked your engine earth?

I had a similar charging problem, which was due to the lack of a 'formal' engine earth.     The original was a manky length of braided strap, that either corrodes away or is lost in a rebuild.    Without it, current must find its way back to the battery via the transmission and more bizarre pathways, like the choke cable!     Check yours - is it warm or even hot?

My problem was cured by fitting a length ofsubstantial cable between the engine block and the battery earthing point (doing it properly!).      Starter cable is best,as the earth must carry the same current as is supplied to the starter.

John

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14 minutes ago, Bobble said:

I have told you the full story as I know it "perhaps not in the right order" but the best that I can offer.  I don't have the technical knowledge to relate all of the more intricate details but I do try.

Sorry.

Bob

You've nothing to apologise for Bob -  its just that many times people have posted problems here only for the real cause  to come out many days later as a 'by the way I didn't say...' remark. I wasn't accusing you of anything, so sorry if my post came across that way. As for your little accident with the wiring - easily done and most of us will have done similar things so your honesty is refreshing. 

Your update is appreciated as it all adds to the body of knowledge - this problem is certainly a bit of a puzzler. Sometimes the result is never revealed once the problem gets fixed, so we never get to know, so please keep us posted on the progress.

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Further thought Bob. Under what circumstance was the 28v measured?  I assumed that was off the car but as usual my assumption may well be wrong.

If it was with the alternator on the car and the engine running, a voltage like that indicates a bad connection between the alternator and the ammeter. 

The regulator in the alternator needs to 'see' the battery voltage in order to work. If that connection is not there, the output voltage will increase way above the normal level as there is nothing for the regulator to compare it against. 

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OK - some progress to report but thanks for further comments.  It certainly wouldn't hurt to ensure that the engine is earthed properly and I will certainly make sure that this is done.

Just had a call from John at Amrest.  In the limited time he has had this morning he has conducted further tests.  Much of his report has gone over my head but in addition to what I have already reported he by-passed the ammeter with the same result as before so no fault there.  All his readings indicated that all was well with the wiring but he decided to "excite" the alternator direct from the battery (I think) rather than through the ignition.  The result was a proper charge indicating that the alternator is definitely not faulty - to some extent this is a relief and I will certainly inform TRGB of this development.

Next job I am told is to check all wiring/connections between the ignition switch and the alternator (and earth strap to engine - thanks John R).  If this all checks out OK then it probably indicates a problem with the ignition switch.  I'll report back once the problem is solved (hopefully later this week).  I am told that the wiring system on the TR4A is quite straightforward but hopefully this will be part of the learning curve for many of us amateurs.

Rob H - I am sure that the alternator was tested on the car and running (I had gone to the loo at the time!).  Could your idea of a bad connection be attributed to the starter switch?  By the way I almost neglected to say that he has had the starter solenoid "apart" with no fault found.

I am feeling a bit more optimistic today.

Bob

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3 hours ago, Bobble said:

Rob H - I am sure that the alternator was tested on the car and running (I had gone to the loo at the time!).  Could your idea of a bad connection be attributed to the starter switch?  By the way I almost neglected to say that he has had the starter solenoid "apart" with no fault found.

 

No Bob, there is no reason why the starter switch or solenoid should affect this.  If the ignition warning lamp turns on with the ignition switch and is brightly lit before you start the engine, and if the engine actually starts and runs, the switch is working OK. The connection point for both the ignition lamp and the coil is from the same place on the switch. That leaves you with the ignition-bulb-to-alternator wiring. 

By the sound of it we are really back to the original suggestion of the alternator field not being properly 'started' through the ignition bulb connection, as it looks like he did the check I suggested in post 9.  I wonder if he made the connection direct from the field terminal to the battery or whether he used a bulb in series ? 

 

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.

Excuse me for enquiring Bob, but in your original post you said that you went out for a night-time drive and your instrument lights were dim ..which led you to change their bulbs for LED ones - but unless I'm misreading it,  you don't actually say whether the ignition warning light was previously flickering.  As you made no mention of it - then might we assume it was not flickering and the alternator charge was previously fine ?  

if so., the engine earth was fine, as was the ignition switch, solenoid  ..as was all else.

And again  if so.,  then ..again from what I gather,  the only thing you changed were the instrument lights (but not the ign. warning light) for LED and the ammeter (with a two rather than three terminal one).  Noted also ; the earth leads to all instruments have subsequently been renewed.

Might I suggest, as was proposed by Roger H -  you isolate those parts in their entirety (unplugging every one of them), and you also temporarily refit the original ammeter (using the three terminals) ..which again you did not say was previously reading low.  Or else bypass it by bridging across the two terminals (..I presume the third terminal was only for its own illumination).  

In short,  bypass everything you changed..  

 

Might I also recommend one of these < here >..   I have one and it works great.   I bought it because another car's battery was weak (from standing many years)  and I wanted to quickly check its state (without even opening the bonnet) and that the car's charging system was working. 

s-l1600.png.920d5a8f8274c7e357df1617f9fec774.png

^ It simply plugs into the cigarette lighter / power point, and digitally displays your battery's voltage.

NB. It doesn't even have a switch, so don't leave it plugged in when you're not in the car.

On my car,   before I start the engine - if it reads below 11.5v  then I know that car will not start (it's a quick and convenient check on a car which I don't use all the time).  If the voltage reads about that figure or above then the engine will start. Once started the voltage goes up to 14.7volts.  That's all it does ..but for £1.53 (including shipping from Hong Kong) it tells me when the battery needs to go on a charger / whether the engine will or will not start,  and that the alternator is working great.  It's very reliable and easier to understand (for a numpty like me) than an ammeter.  And of course it plugs into other cars ..so is handy to keep in a tool kit.

Pete

 

Edited by Bfg
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Hi Bob

if your still have the warning light glowing after all the other checks  it sounds that there is a high resistance (bad connection) in the warning light circuit. If you can understand with the ignition on 12v is fed via the small wire to excite the alternator when it starts charging the current on this wire is equal and so light goes out ie it loses its earth through the alternator. Who ever did the conversion should have used the old dynamo voltage regulator as a connector block what I mean is removed the innards , and this bit you should take note of , joined all the large wires together from terminals A .A+ and D together(brown/green, brown/ white and brown/blue) the two small wires{brown/yellow) which are the warning light wires together ,this is where you might have the bad connection and left the earth wire disconnected. I would double check all connections in this area        

 Hope this makes sense Chris

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Bob: Might be worth reading my original article about conversion to alternator, now to be found in Section J4 of the Technicalities CD.

In addition, James Christie and I published an article about fitting the Moss alternator kit - this can be found in TR Action 248 (March 2011), which is available on-line through the Register's main site.

If you can't find these, send me a PM with your email address and I'll forward MS Word versions to you.

Ian Cornish

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  • 2 weeks later...

Sorted!

First of all a big thank you to all those of you who took the time to help with my problem - all suggestions were quite valid and ensured that everything was checked out.  Chris's comment above made us revisit the old regulator box despite having previously checked the connections and found them to be OK (we thought).  I hope that the following explanation follows the briefing from the auto-electrician closely enough to make some sense.  You will have gathered that my own expertise is seriously limited.

When I converted from generator to alternator part of the process involved joining all the terminals in the old regulator box as this function is now performed in the workings of the alternator itself.  Basically, my method of linking the original terminals was to screw a copper strip across the five connectors and replace the box on the inner wing to retain some level of authenticity.  This has worked perfectly since the conversion and it was not obvious why it suddenly decided to malfunction at this point just because I changed the ammeter and the dash bulbs.  From the comments in this post it will be obvious that we tried "everything" that could possibly be the root cause of the problem.  However, while conducting further tests inside the old regulator box with a multi-meter the battery started to accept a charge somewhere just over 14 volts.  It turns out that one of the five screws used to fix the copper strip had come loose and the pressure applied by the muti-meter probe exerted enough force to ensure a more secure contact.  With all five terminals now securely attached to the copper strip (using tiny nuts and bolts rather than screws which can turn in the original connectors without actually getting fully tight) we have a proper charge from alternator to battery "under load".

I am not sure that this makes any sense to the more knowledgeable owners out there but it seems to me that I could have saved a great deal of time, effort and head scratching if I had done a better job in the first place.  Was it just coincidence that made the connections malfunction at the same time that I fiddled with dashboard instruments?  Who knows but we are up and running again.

Once again, many thanks for the help and advice received from this forum - it's brilliant.

Regards

Bob

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Glad you've fixed it Bob. You must be relieved after such a saga. 

Thanks for posting with the solution.

 

 

 

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Well done, Bobble!

I fear this demonstrates the verity of the adage, "When something goes wrong, it's due to the last thing you did!"

Did you mention that you had converted from dynamo to alternator?    If so, that was the clue!

JOhn

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John

At the time I didn't feel that this was the problem as it had been working quite well for around four years following the conversion.  The previous work carried out was ammeter and dash bulbs so I was tending to suspect these were the cause.

All done now and a further bit of knowledge to add to my tiny database - probably won't need it again!

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Here’s my alternator wiring. It’s a modern small alternator - three terminals including the big one back to the battery.

Something is wrong as the ignition warning lamp doesn’t illuminate. Checked and it’s not that!

Separate ignition controlled fuse box feeds a supply to both the alternator and warning lamp. These are off the same fuse but I cannot see why that should cause any issue. If needs be, I can take the lamp feed and feed to the alternator from separate places.

The cable from alternator to the warning lamp is also there. This should provide the earth when alternator not generating charge back to the battery.

So, you can see that in theory the wiring seems correct, but the warning lamp isn’t working.

I  could do with this not being the case for a variety of reasons including knowing that the fan belt hasn’t fallen off or failed leading to no water circulation and overheating - it’s a race car!

Help gratefully received.

Thanks in advance.

David

 

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Three questions Dave:

1) Has it ever worked?

2) What alternator is it (make and type)?

3) Is the battery getting a charge?

14 minutes ago, david ferry said:

The cable from alternator to the warning lamp is also there. This should provide the earth when alternator not generating charge back to the battery.

That bit is unclear. Can you add more detail as that is obviously not standard TR. A diagram would help. 

Some alternators have the warning lamp connected to earth rather than to supply.

Edited by RobH
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Variety of alternators tried. All small alternators of the Kubota/Brise type.

Pretty sure the battery is being charged but intend to check this next time I’m in the workshop.

The car is a new build so no alternator has yet worked. The alternator currently fitted has previously worked. It has a Bastuck label stuck to it.

Hopefully, wiring diagram attached. This is as described in the post I made a little earlier, hence my lack of understanding of why it’s not working.

David

654C3704-0E87-4978-A799-D1BF0E6456A7.thumb.jpeg.49351de5d3a1f90ac370a7353f0bef42.jpeg

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Well if that was the wiring diagram supplied with the alternator, your setup sounds identical apart from the fuse which should make no difference. If you have done an end-to-end continuity check on the wires in the two-pin plug there isn't much else.  The only other thing is the earth connection to the alternator body. 

Did you test the bulb by earthing it's connection in the plug? 

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All sorted. Replaced alternator having established that the wiring was correct and working properly.

End result is a properly working ignition warning lamp.

Interestingly, the replaced alternator was in fact charging the battery, it’s just the warning lamp side of things that wasn’t working properly. The reason for this was that the earth terminal wasn’t/isn’t going to earth when the engine isn’t running. I may open it hand see if there’s anything obvious.

David

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