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Ignition light on, but Alternator appears to be charging

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Night before Gurston after preping his car, Chris comes back in after a quick test run and says Oh by the way I forgot to say but my ignition light has been on a lot when I've taken it out this week.

Is it on Now!?

Yes

Bugg.r (why do these last min jobs always happen?)

Voltmeter seems to be reading about right place, Battery showing around 13+ volts.

Fiddle with the plug on back of alternator, its a bit close to the front header pipe on the V8, so alternating between desperately trying to avoid burning on that, whilst going ouch as my arm touch the hot expansion tank.  Occasionally whilst fiddling with the wiring the ignition light dims then comes back, did flick out once but came back. 

Getting late in evening, early start, car going to be driven 2+ hours in the morning, and then 2+ back later.  Ok seems to be charging but put two spare batteries on charge over night, plus will have other car on trailer so have some options if alternator does fail.

So question what, why would ignition light come on if alternator is charging OK, clues to initial tests?  

Alan

 

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So what actual voltage is it holding at when running?  Wants to be  13.8 - 14.5 ish.  If below 13.8v then the answer is probably that it's charging a bit and might work ok for a while running round in dry daylight, but will all go pear shaped (or dark) when driving in a dark wet night.

Could be a crappy connection (esp if the multiplug and wires are a bit crispy), could be voltage reg on way out, could be brushes worn right down or might be a popped diode.

Nick

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I had wondered, the tr7/8 dash electronics are not wonderful ever, and rely on a lot of voodoo to keep all the lights and instruments working at the same time :biggrin: there are a couple of instrument lights on the blink "literally" so could be worth a good look, I'd just assumed failure was a likelihood, not sticking on.

alan

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OK had plug out, contacts nice and clean, and wiring good and firm, Fairly sure this car had a new loom in 2005-2007 period.

Ignition light on and dim at idle (circa 800 rpm) gets brighter as you bring the revs up.  Voltage at idle 17/18V rev it goes to 20/21V measured at battery in the boot,  so I guess its the Alternator breaking down and time to send to Alternator Repair Man?

Alan

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Regulator is shagged. What type of alternator is it? regulator is a very easy swap on some (e.g. Bosch) and can be done in situ.

Battery may be clapped also, depedent on how long this has been going on.

Nick

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Thanks Nick!

Don't know make, will take a look in the morning, this is normally the point where I tell him take it to a friend of our garage, who will easily order and and fit what is required (that way I avoid breaking something which I have to spend even more unpaid time fixing!)   I like doing the interesting stuff on the TR8 not the routine stuff :thumbsup:

Apart from the Gurston run and back I suspect its only done a couple of very short trips, car lives here and it only went out a couple of times the preceding week. From way battery is behaving it seems OK at the moment, but will get it tested to see if its fried!

Alan

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Surprised the battery didn't barf it's guts if it's being seeing 20+ volts for a couple of hundred miles.  Generally there is a sulphurous stink as a warning.  Perhaps the voltage hasn't been that high all the time.  Worth checking battering electrolyte levels if you can actually get access as it is likely to have been gassing a bit!

No issue with telling him to take it to the garage - just saying!

Nick 

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Hi Alan,

I would suspect the voltage regulator module.

But, I suspect the voltage you are measuring as suspect as well. At that voltage; you would have lights like the sun and your bulbs would have half the life of a fruit fly.

As mentioned above; your battery would be past dead by now.

If it's a modern replacement alternator you have, I have loads of new 14.2V- 14.5V regulators. You are welcome to one FOC.

In the unlikely event that the battery is charging at over 15 volts; you will be generating a nice explosive mix of hydrogen and oxygen!

Cheers,

Iain.

PS. send a picture of the rear of the alternator where the regulator is mounted.

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32 minutes ago, spitfire6 said:

I would suspect the voltage regulator module.

But, I suspect the voltage you are measuring as suspect as well. 

In the unlikely event that the battery is charging at over 15 volts; you will be generating a nice explosive mix of hydrogen and oxygen!

Chris took it to a friends garage yesterday, voltage is fluctuating all over the shop from 9V up to 17V on their equipment. Its a Lucas unit, so they have just ordered a new one for fitting next week (and keeps me out of the loop).

If its an explosive mix, good job its in the boot next to the fuel tank!

Alan

PS thanks for the offer of a regulator, if I ever drag the Vitesse into the modern charging world I may appreciate.

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