04. C70. 80K miles. 2000 ragtop.

Anyone know where to find / battery charging data? I have seen a lot of data but not in simple english.

history of problem.
Having a few sudden flat batteries a new battery fitted 6 months ago (AA said it was knackered)
1 or 2 flat batteries since.
last night no start again, AA put volt meter on (battery only) & said 11 volts, its yer .
No warning lights, checked voltages today myself, at 3k revs battery shows 13.16, Alternator shows 13.23 is this ok or low?
Battery + lug was loose & the B+ cable snapped easily at the terminal.
removed said cable tested fine so soldered new end on.
readings at battery & alternator are the same as b4.
Cant understand why it was at 11V last night,, regulator?
I aded some long cables to my volt meter and went for a spin, started off at over 13V, as it got hotter voltage dropped, after 10 mins driving battery was 11.9V = is it heat related?.
Only other electrical issue is the brake lights stay on sometimes, I thought this is why I had the odd flat battery. (its the switch sticking)

 

Have auto parts store do a complete battery/starting/max load test, its free. Also Batteries Plus/Bulbs will do it free. I would replace that switch. Do you have the right rear fog light option ? I do.

 

no 1 does anything for free in birmingham uk :-(

developments = I decided to tackle the jobs I knew needed doing (I have a fault reader)
replaced
1 X lamba censor
1X blown bulb in E/management dash light
1X Coil that had intermittent error
then the battery warning light comes on :-(
meter says less than 13 V constant at battery
checked V at alternator again less than 13V
All warning lights are now out but I know the alternator is faulty so will swap that out the weekend or maybe change the regulator in it?
I think alternator has been the problem all along, I had gut feeling the old battery was ok as it was a large one off my diesel mondao that was 2 years old
odd how the battery light cam on when it did though
I hope this is not the start of my C70 being a money pit as I really like the car
BobT

 

Highly possible it is down to the regulator needing renewal.
I would start with that and see what happens, after all you know the alternator does in fact charge,even if variably.
Presumably the drive belt is okay and tensioned adequately?

 

Sounds like the altnerator or voltage regulator is bad. Typical test voltages should be 12.6 for the battery with engine off, 14.5ish for engine on at speed (say 1500+ RPM) maybe 14.x at idle, and 13.high at idle when fully loaded (blower on full, high beams on, rear defrost on, AC/DC CD playing loud etc). The voltage regulator is designed to keep voltage from exceeding a set amount (ie to limit the max to say 14.9V) but if bad, what happens is as the current demand goes up (like charging a drained battery, powering the accessories) if the system can push enough amps, the voltage goes down. Your voltage output is low so you can either try replacing the regulator or the entire unit. (if you install a new/rebuilt alternator you'd get a new regulator).

 

Is that what I was doing wrong.. I was playing Black Sabbeth.
The regulator guys need a number from alternator, need to remove alternator get number re fit alternator. will go to the breakers and get a used alternator up one of the days, been too busy to do so. will get some speakers too. what they like to fit? seems ozzy blew all of em :-(
BT