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Finding a stray load


RAW1969
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Brand new member. First post. Please go easy!

 

Just bought a Mk1 Vitesse 2L and its battery is draining overnight. Following the Haynes manual trouble-shooter suggestion of "find fault and rectify"....I'm searching....

 

The car's had its original dynamo upgraded to an alternator some years ago by a previous owner.

 

I've taken the battery out and measured the resistance across the connectors and have 15Ohms. I've disconnected all the connectors from the fuse box one by one and re-measured across the battery terminals - to try and isolate the circuit the fault is in. Nothing changed. So I'm none the wiser.

 

Concluded the alternator was the problem (as pulling the fuses had no effect) - so have taken it out and had it bench tested. It's giving readings of 14V and 20A. The guy testing it suggested 20A is a bit weak - but he didn't think it was the source of the drain.

 

The alternator was bench tested as the car currently struggles to turn over on the recharged battery, won't fire up and battery soon tires. (So car won't start anymore - it did when I first got it a few weeks ago). The alternator testing guy suggested it might be the starter motor that's at fault. Not sure why that would drain the battery with the ignition off though.

 

The other thing I've noticed is that the part of the loom at by the bonnet hinge is unbound & a couple of the wire look like they've been caught as the bonnet's shut on them at some stage. Will fix in due course - but don't think this is the main fault. All the lights/ horns work fine. 

 

Any thoughts/ suggestions on the next step in the process of elimination would be much appreciated!

 

Richard

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Not sure about the Vitesse but The GT6 has no fuses for the headlamps!  Battery, to light switch, to lights. Triumph were a bit cavalier about fuses!  So there maybe some battery drain there. I would disconnect the alternator and battery and measure again. 

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I don't know if this will be it but I had a similar issue - mine was two issues, I had a slow discharge through the starter solenoid which I replaced, plus the battery was knackered anyway, replaced that and no problems since plus I'm still on a dynamo!

 

Aidan

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Thanks for your comments - I'll follow these up.

 

Just to add - the battery is new (not to say it's not already suffered some harm though?).

 

Also - I'd disconnected the alternator and measured 15Ohms to ground off its "big tab" - it was on this basis I'd taken it out to get it bench tested. Is there a chance it can be "working" (ie giving 14V and 20A) - but still be the stray load?

 

Suspect as Aidan suggests there's more than one thing going on with it!

 

Richard

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Here is an interesting link, a bit rambling but 2/3 of the way down he suggests a much lower resistance on the alternator.

 

http://kawtriple.com/mraxl/trbl_alt.html

 

I believe if a diode is gone in the diode pack you get a higher resistance. I had to replace my diode pack (my son-in-law reversed charged my battery! Bang!) It's an easy enough job.

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Power loss from a failed diode is a good possible, also indicsted by the low charge rate

 

there should be no current drain or resistance between the alt and the battery ,

 

as the diodes should close this down. If one in the bank has failed then current passes both ways

not just one way

 

connect a panel lamp bulb between battery post and its terminal if it lights there.s a loss going on

so then you just keep disconnnecting or dis bulbing till you find the action that puts the lamp out

 

pete

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Many thanks for your comments. I'll admit there's a degree of assumed knowledge that I just don't have - being at the start of the learning journey.

However - I'm thinking what you're saying is that even though the Alternator "passed" the bench test - it may still be the culprit & I now need to find out if one of the diodes has failed. Presumably the diode pack replacement referred to by Doug then applies.......

 

I'm sure I'll get there sometime!

Thanks again

Richard

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Such a small drain current is likely to be small enough to measure with your Multimeter - they can usually tackle up to 10A.

 

So start at the battery and check that there is such a small current when the ignition is off.   And fripperies such as clocks disconnected.

If there is, trace it through the loom, using the circuit diagram.  EG next is the starter solenoid, which has three ways the current could go, starter motor, starter switch and control box.

Obviously the possibilities multiply after that, but your meter will light the way, and lead you to the short circuit, or faulty unit.

 

Method makes all simple, or as Holmes would say, " when you have eliminated the impossible, whatever remains must be the truth"

So much better than guessing.

 

JOhn 

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Thanks again for comments/ suggestions.

 

Had another tinker last night. Put it all back in the car. Battery disconnected. Alternator disconnected.  Resistance between battery's earth strap & big tab on alternator is 15 Ohms. Can't help but think this is a problem. BUT then connected alternator & connected battery to earth and put multi-meter in series with battery's +ve post and could see no current at all reading even on the most sensitive setting. No sign of a trickle.

 

Also tested battery by putting headlights on - looks fine (no sign of them dimming).

 

Out of curiosity I then tried to start the car - it started second time. Voltage across battery 13.5V. So the whole "car won't start" scenario looks like a red herring. 

 

Next set of newbie questions:

- Having not looked closely at the "other" side (offside) of the engine before now (been staring at the alternator for weeks) - it looks like access to the starter solenoid (and more so the starter) - is a bit tight from above (big hands). Is it better accessed from below? Or better with air filter off?

 

- If I do settle on the problem being in the alternator - my decision then would be "replace or repair". Replacement unit would have warranty - any thoughts?

 

- Alternator - labelled LRA100 - which I understand is an older version of ACR15 or ACR17? The guy at the alternator place suggested that the 20A output was weak - and that a replacement he'd sell would push around 50A. Is that excessive? Is there a way to tell what the unit is from the label (there are some other numbers alongside LRA100) - I'll need to know that before seriously contemplating a repair.

 

As you will see I'm no Sherlock Holmes.......and the electronics I learned at O-level seem a lifetime ago.

 

Your time spent replying is very much appreciated.

 

Thanks

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Any of the lucas ACR alernators will be fine (as long as they have a built in regulator, most do. And it is correctly handed, though that is easy to swap)

 

Plenty available, and reliability seems better these days, a few years ago new units were terrible. And in all honesty they are not expensive either. Buy from a reputable supplier.

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you may find the old wire from the alt to the control box in the left foot side well is poorly co joined to convert from dyno to alternator. ,best remove it and run a good sized cable direct from alt to starter solenoid, ( if thats the case)

 

On recon alternators it was found common that  a failed diode would just be cut off at its stem wire ,  solves the warning lamp glow and drops the charge capability,  saves fitting a regulator  .....nice box. and clean though.

 

 

easy to check the diaodes on these packs with a multimeter on ohms as it will pass current only one way if you get a reading when reversing the probes

its gone .

 

Pete

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In the immortal words of Steffi Graff when a spectator shouted "Will you marry me?" She replied "How much money do you haff?"

 

If your a skinflint like me, repair it. If you've got the dosh get a newer model with a warranty. The increased output is not a problem. 

 

You can do the starter motor from the top. Easiest to take off air filters and side panel (if you have it!). Once you've got it off clean up the shaft but, do not grease or oil it, this attracts crud and makes it worse than before. I'm told graphite, pencil lead, is good to lubricate it.

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Yes I expect that is true!

 

One further question on the Lucas alternator. The brass bolts that appear to hold the plastic cover on. Am I right in thinking I need a box spanner to undo them and if so can anyone confirm size. Guessing 3 16ths? But knowing would be good before buying the wrong tool. Thanks chaps.

Richard

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