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Charging Issues


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Hi All,

My TR5 has presented me with a new challenge! A few weeks ago I went for a long drive out with the West Wales based TR Group. It was a baking hot day and the car ran perfectly. At the weekend I decided to run up the engine and unusually it didn't start first time so the engine was cranked for a while. I tried again and the battery was unable to crank the engine. The car has a battery isolation switch so was most surprised. I put the battery on charge and was able to start the car readily. On start up the ignition light goes out but I noticed that the ammeter remains in discharge. I did some tests with a multimeter. The initial battery voltage was 12.57V but when the car was running this dropped to 12.06V at idle. Does this mean that the alternator has failed? Are there any other tests I could do? The alternator is a Lucas 15AC unit.

Many thanks.

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Yes  - sounds like a duff alternator.  It is a bit odd that the ignition light goes out though. It might be that the main rectifier stack has failed, because the warning light is driven from a separate set of diodes and that bit may still be working.

You might struggle to find parts to repair a 15AC yourself. One option is to replace it with an 18ACR - not a straight swap as the wiring is a bit different but at least it has a decent output whereas the 15 is decidedly weedy.

Edited by RobH
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Hi Rob,

Thanks for your reply. Do think it might be worthwhile changing the brushes and rectifier rather than sourcing a replacement alternator? I can get both from Rimmer Bros.

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Worth a go if you can actually get the bits. Do Rimmer really have them?  It has to be for the 15AC - I don't believe that parts for the ACR type will fit.  Failing that you might find a specialist who can repair it for you. 

Before you do though, one thing worth looking at is the regulator. If you have the four-terminal version, one of the terminals is a battery-sense wire and that may have a bad connection.  

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Hi

I agree with Rob you could hunt around for the correct parts for the 15ac alternator some time ago (many years) you were able to pick up an overhaul kit but I think these are now hard to find I would be inclined to look for a local auto electrical repair company who could repair or may have some old stock

Chris    

 

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Hi All,

I'll check out the connections on the regulator before removing the alternator. I have found a company called Carl's Starters and Alternators that are based in Tredegar, which is a short drive from me. I have spoken to them and they are confident that they can fix it. I am keen to keep the period Lucas 15AC alternator, so if I can get it repaired then so much the better. I am relieved that the alternator must have failed towards the end of the drive out I mentioned as I must have been running on battery only!

Thanks for your help.

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On 8/24/2021 at 2:25 PM, DenisMc said:

Hi All,

I'll check out the connections on the regulator before removing the alternator. I have found a company called Carl's Starters and Alternators that are based in Tredegar, which is a short drive from me. I have spoken to them and they are confident that they can fix it. I am keen to keep the period Lucas 15AC alternator, so if I can get it repaired then so much the better. I am relieved that the alternator must have failed towards the end of the drive out I mentioned as I must have been running on battery only!

Thanks for your help.

You might be advised to take the control box as well to the alternator repair people, perhaps they will be able to check it after the alternator has been repaired and confirm it works with the alternator.

Moss do still sell the carbon brush set GGB503 - all other bits are now not listed.

Peter W

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50 minutes ago, tr graham said:

It’s easy to damage those alternators if you do not disconnect before using a modern battery charger

Are you sure about that Graham?  Technically that would be very odd. The rectifier diodes in the alternator should block any current flowing from the battery into the alternator, so there is no reason why damage should occur unless the charging voltage rises to silly levels - which cannot happen if the battery and its connections are OK.  

 

 

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  • 2 weeks later...

Hi All,

I removed the alternator and Carl Evans of Carl's Starters and Alternators repaired it. A very quick turnaround and £28. He replaced the brushes as one of the connections had failed. All is fine now with the battery voltage at about 13.6 V at tick over going up to 14V if I rev it up. Before I removed the alternator I noticed that the jacket over the 3/8" Lucar power connector had melted at some point. In fact the connection had corroded quite badly. Carl cleaned up the blade and I the connector with some wire wool, Though a bit of trickery I managed to fit a new jacket. However, after running the car up in my garage I noticed that the new jacket had melted! The Lucar connector was a loose fit so perhaps it was a high resistance connection. I have now tightened the fit and it doesn't seem to be getting as hot. Should I still have the problem, is there anything else I should check?

Thanks,

Denis

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Nothing else to check Denis - a high-resistance connection will get very hot if you pass a lot of current through it.  The Lucar should be a pretty tight push as in "go on you B*****."  If it slides on easily that is not good.  Bending in the edges and making sure it is clean and shiny metal usually fixes things. 

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