Viva GT under-charging alternator issue

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Viva GT under-charging alternator issue

Postby Colin » Fri Nov 18, 2016 8:26 pm

My Mk I Viva GT runs a standard alternator with separate voltage regulator. This is just about okay for normal daylight running, however I found that running it under load on the way back from the NEC last Sunday - in the rain, with lights and wipers operating, the car began to lose battery power.

The lights gradually dimmed and the wipers slowed to a virtual standstill over the cold, wet, sixty five mile drive home. I just about made it!

The alternator was last checked about five years ago and was charging okay at that time, but the issue was apparent even back then. Obviously I don't usually drive it on cold wet nights!

Can anyone suggest a possible cause or suitable upgrade? My GT has a standard spec 1975cc engine (and 48 year old wiring!)

Thanks very much.
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Re: Viva GT under-charging alternator issue

Postby Fred Dukes » Sat Nov 19, 2016 2:00 pm

Best solution I would think would be to go for the self contained alternator with the DC conversion in the in the alternator as fitted to the HC OHC models. I think the type is covered in the Haynes manual ( its not in the factory training manual) and the wiring differences can be worked out.
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Re: Viva GT under-charging alternator issue

Postby Colin » Sun Nov 20, 2016 7:24 pm

Thanks for that, Fred. I will research some suitable alternatives as suggested. :D
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Re: Viva GT under-charging alternator issue

Postby StefanM » Wed Nov 23, 2016 10:48 am

if the output is the same a modern alternator will not give any improvement. I would suggest that you repair your existing parts and make shure everything is 100% ok instead.
This particular Lucas setup is not the worlds most reliable system but I think that you should retain the original system as long as possible. Especially if it has not been modified in the past.
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Re: Viva GT under-charging alternator issue

Postby jpsmit » Wed Nov 23, 2016 3:25 pm

I am inclined to agree with Stefan, these are not complicated beasties. I once had an alternator under charging due to the amount of dust in it (Saskatchewan roads) no one believed me - took it apart, cleaned it and it was fine. Sounds like your brushes might be getting worn - not a difficult fix and certainly cheap enough to try first.
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Re: Viva GT under-charging alternator issue

Postby Colin » Wed Nov 23, 2016 11:58 pm

Thanks both. That does seem to make sense. A forty eight year old alternator with 120,000 miles under its belt is surely going to be worn!
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Re: Viva GT under-charging alternator issue

Postby ADRIAN » Thu Nov 24, 2016 12:02 pm

My own experience is that the fan belt must be good and tight, and no slipping. Thought that Ebay item number 252649830678 could be a useful spare? Adrian
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Re: Viva GT under-charging alternator issue

Postby Colin » Thu Nov 24, 2016 1:16 pm

ADRIAN wrote:My own experience is that the fan belt must be good and tight, and no slipping. Thought that Ebay item number 252649830678 could be a useful spare? Adrian


Thanks, Adrian, that will indeed be a useful spare, although my car had a new voltage regulator five years ago too.

My understanding is that the voltage regulator converts the alternating current produced by the alternator into the 12V direct current used in the car's various electrical systems. Hence if the voltage regulator fails then obviously the charging system won't charge and the battery will very quickly go flat.

Another symptom is that the battery goes flat if the car is left with the battery connected (and obviously the ignition switched off) for more than a day or so - which would tend to indicate a short somewhere in the ignition or lighting circuits between battery and ignition / lighting switches....

I'm not the brightest spark (sorry!) but I think I might be onto something here.... :lol:
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