Alternator charging
Discussion
Hi all , just put my engine ancillaries back on after manifold / hoses replacement on my v6 S3, on the first run out today the voltage gauge shows charging very slightly over the lower red line although the battery charge light never came on , my question is could this be down to an undertensioned belt ?
I have tensioned the belt to around 1.5 cm flex either side of the belt static position.
The alternator charging was fine before I messed around and used to charge at around the 18v mark.
Any ideas chaps ?
cheers/regards Paul.
I have tensioned the belt to around 1.5 cm flex either side of the belt static position.
The alternator charging was fine before I messed around and used to charge at around the 18v mark.
Any ideas chaps ?
cheers/regards Paul.
Hi guys , sorry I haven't responded sooner , [lure of the kebab was too much !] , I did wonder if it was overcharging myself ,I think a check with a meter as Mike suggested will be the first port of call.
Just one other thing I noticed was the battery light does not come on when I switch on the ignition before I start the car , was that usual ? I cant remember if it is or not,
The earth may be worth looking at too although I never had any charging or battery probs previously .
Im not even sure if this IS a problem as the needle sits just above the red ,im just not sure what the correct charge reading on the voltmeter should be ,the voltage does rise slightly on high revs .
I really don't know .
Cheers for the help so far guys ,
cheers/regards Paul.
Just one other thing I noticed was the battery light does not come on when I switch on the ignition before I start the car , was that usual ? I cant remember if it is or not,
The earth may be worth looking at too although I never had any charging or battery probs previously .
Im not even sure if this IS a problem as the needle sits just above the red ,im just not sure what the correct charge reading on the voltmeter should be ,the voltage does rise slightly on high revs .
I really don't know .
Cheers for the help so far guys ,
cheers/regards Paul.
The red ignition light should come on with the ignition and go out with a "few revs".
If it's not working (bulb blown?)the alternator won't start working and hence voltmeter will read low!
A fully charged battery should read about 13.2 volts, yours may read a bit less then drop even further as you crank the engine over but voltmeter should then rise to 14 or so once engine is running and alternator is "doing its job"
Hi Mike , thanks for that info , I will check that out with the meter , yes I can remember the battery light going out after giving it a bit of revs after starting , I was more thinking did the battery light come on after two clicks of the ignition key prior to starting ?
Still had a good 20 mins of flying about in the sun today , lovely it was too !!!
cheers/regards Paul.
Still had a good 20 mins of flying about in the sun today , lovely it was too !!!
cheers/regards Paul.
Paul,
to answer your question; on my S2, the red battery 'caption' is lit at the point of second stage ignition, turnover and idle until the engine is revved when it goes out. I believe the revving 'excites' the charging circuit and at the same time the battery caption clears and my voltmeter then indicates a 2-3V rise (surely varies between each S!).
Earlier this year I had what I thought was a charging fault that sounds similar to yours. I had no battery light at any stage of ignition and the indicated gauge voltage remained low even when the engine was revved a little. However, at considerably higher revs than usual the gauge would begin indicating 2-3V higher as if the alternator was now charging. I found out (from this forum) that the alternator has the ability to 'self-excite' at high enough revs. This is what I was experiencing. The source problem was as simple as the bulb for my battery 'caption' was damaged. It is a very specific rating of bulb (5W?) that must be replaced like for like as it is a critical part of the automatic charging circuit. I was able to repair mine with some solder and the problem was solved.
I hope this helps and that you sort your charging problem soon.
David
to answer your question; on my S2, the red battery 'caption' is lit at the point of second stage ignition, turnover and idle until the engine is revved when it goes out. I believe the revving 'excites' the charging circuit and at the same time the battery caption clears and my voltmeter then indicates a 2-3V rise (surely varies between each S!).
Earlier this year I had what I thought was a charging fault that sounds similar to yours. I had no battery light at any stage of ignition and the indicated gauge voltage remained low even when the engine was revved a little. However, at considerably higher revs than usual the gauge would begin indicating 2-3V higher as if the alternator was now charging. I found out (from this forum) that the alternator has the ability to 'self-excite' at high enough revs. This is what I was experiencing. The source problem was as simple as the bulb for my battery 'caption' was damaged. It is a very specific rating of bulb (5W?) that must be replaced like for like as it is a critical part of the automatic charging circuit. I was able to repair mine with some solder and the problem was solved.
I hope this helps and that you sort your charging problem soon.
David
Hi chaps , steve thanks for the info re the alternator brushes , that's handy to know , David , your problem sounds exactly like what I have now so I think I will check the bulb first . Is the bulb awkward to change can you remember ? I won't be doing much till the weekend but will update as soon as I have more info . Once again thanks guys for the info / help , what a great forum this is , I wish I could help others a bit more but alas I'm a relative newbie to the S series . Cheers/regards Paul
fozzy280472 said:
Is the bulb awkward to change ?
.... It's a TVR, what do you think !The bulb holder just pulls out from behind the dash, access may be a little awkward with steering column and so on getting in the way a bit.
Careful you don't disturb anything else while messing behind there
I believe if you change the bulb to a different wattage it just changes the "exciter" threshold (often down rather than up) so it's not a big deal really.
In fact IIRC changing it to a slightly higher wattage bulb might make the exciter kick in without the need to rev it to ~2k to excite the alternator. I doubt it's worth experimenting with though LOL.
In fact IIRC changing it to a slightly higher wattage bulb might make the exciter kick in without the need to rev it to ~2k to excite the alternator. I doubt it's worth experimenting with though LOL.
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