Member Since: 05 May 2016
Location: Stockport
Posts: 96
Think Alternator is dying Help. Think its fixed its self
Hi guys think my alternator is on its way out as usually 14.5-9v then dropped to 12.7 😭
Also just realised when car is idling the voltage is around 12.7 & also when driving & accelerating but when you let off the accelerator the voltage then jumps upto 14.5v then drops when accelerate
Last edited by RickoD3HSE on 6th Jan 2019 10:42 pm. Edited 1 time in total
5th Jan 2019 4:29 pm
eightfoot
Member Since: 12 Apr 2015
Location: sunny essex
Posts: 762
have you just done a battery reset by any chanceplease excuse any grammer/punctuation mistakes,i'm thick,thankyou
current vehicles 2005 d3 2013 d4
5th Jan 2019 4:49 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4629
Either the alternator is on the way out or the belt is slipping, the latter being much less likely. Check the tension and if OK its new alternator time before it takes the battery with it.yµ (idµ - eAµ) ψ=mψ
5th Jan 2019 4:54 pm
RickoD3HSE
Member Since: 05 May 2016
Location: Stockport
Posts: 96
eightfoot wrote:
have you just done a battery reset by any chance
Hi no not done a battery reset but i have replaced the battery boxing day with an Exide EA1000 that was the same as what was on it but to be honest it didn't need replacing.
5th Jan 2019 5:30 pm
RickoD3HSE
Member Since: 05 May 2016
Location: Stockport
Posts: 96
PROFSR G wrote:
Either the alternator is on the way out or the belt is slipping, the latter being much less likely. Check the tension and if OK its new alternator time before it takes the battery with it.
Well ive just been & bought a Denso Alternator from ECP
& got back in the car to drive home & everything seems to be working as it was this morning now showing 14.1v on idle 🤔
i have also double checked voltage on my proper volt meter which is showing the same charging rate.
Belt & tensioner etc are perfect btw
5th Jan 2019 5:38 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4629
Above 15v is what you would expect from a cold start, dropping back to around 14.7 at idle when warm. The fluctuations you are experiencing are typical of an alternator about to fail. Looks like you will have a busy day tomorrow. yµ (idµ - eAµ) ψ=mψ
5th Jan 2019 6:32 pm
eightfoot
Member Since: 12 Apr 2015
Location: sunny essex
Posts: 762
RickoD3HSE wrote:
eightfoot wrote:
have you just done a battery reset by any chance
Hi no not done a battery reset but i have replaced the battery boxing day with an Exide EA1000 that was the same as what was on it but to be honest it didn't need replacing.
this is not the correct batt for your car,think you should have a agm batt fittedplease excuse any grammer/punctuation mistakes,i'm thick,thankyou
current vehicles 2005 d3 2013 d4
5th Jan 2019 7:09 pm
RickoD3HSE
Member Since: 05 May 2016
Location: Stockport
Posts: 96
PROFSR G wrote:
Above 15v is what you would expect from a cold start, dropping back to around 14.7 at idle when warm. The fluctuations you are experiencing are typical of an alternator about to fail. Looks like you will have a busy day tomorrow.
yeah the voltages have been all over the show today & nearly back to normal this evening but not the same as last few weeks. looks like a date with the disco tomorrow
thanks for your input
5th Jan 2019 8:07 pm
RickoD3HSE
Member Since: 05 May 2016
Location: Stockport
Posts: 96
eightfoot wrote:
RickoD3HSE wrote:
eightfoot wrote:
have you just done a battery reset by any chance
Hi no not done a battery reset but i have replaced the battery boxing day with an Exide EA1000 that was the same as what was on it but to be honest it didn't need replacing.
this is not the correct batt for your car,think you should have a agm batt fitted
it is a 2010 none start stop D4, my mate works for guy salmon & found out the original battery was a Varta 90Ah 900CCA wet battery so assuming it lasted 4-5 years the 2nd fitted was an Exide EA1000 100Ah 900CCA so assuming that was 3-4 years when i changed it for a like for like it is the right battery
Last edited by RickoD3HSE on 5th Jan 2019 10:24 pm. Edited 1 time in total
5th Jan 2019 8:16 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26701
Ricko, I wouldn’t be too hasty spending your money, I think your car is behaving like it should.
D4 does have a smart charging capability which will cut the alternator output when the engine is under load, and increase the alternator load when cruising or decelerating. I have a volt meter like you, plugged in the same place and regularly see what you describe.
When it’s cold, the car puts the heated screen and rear screen on itself, in this situation the volts will be low.
5th Jan 2019 9:37 pm
RickoD3HSE
Member Since: 05 May 2016
Location: Stockport
Posts: 96
Hi Gareth,
Thanks for you reply, in a way i know what your saying & i'm not convinced there is a lot wrong either as we haven't had any warning lights/bongs (touching wood) or anything it runs beautifully its just what we have been used to seeing on the volt meter over the last 2 months when stationary with engine on/off & when starting & running etc that after it started showing no charging today its got me a bit worried as we are going on a family holiday with 11 month old to Aviemore beginning of Feb & trying to iron out any problems if poss before we go away.
It was showing 12.6 before starting, started no problem then 1st few seconds gradually rose 12.9 13.2 13.8 14.3 14.8-9 we went few miles other side of hazel grove to pick something up i sat in car running while wif popped out then went to esso garage at the Fiveways where i got out with Smart key & went in shop & left wif in car running when i got back in & went to put car into drive that's when noticed battery voltage dropped to 12.2 & not doing much more even when driving & pretty much been like that through the day untill i went ECP bredbury about 3.30 & bought alternator got back in started it up & all seems back to normal
Before i fit new alternator im maybe going to see how it is over next week & check the obvious battery terminals, earth straps etc tomorrow
5th Jan 2019 10:56 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26701
What you are seeing is normal when you have a fully charged battery. If you have recently fitted a new battery, that figures.
If I were you, I’d keep the new alternator as a spare in the car, and don’t worry too much at this stage.
If there are no warning lights, and the car is behaving itself, I’d let a sleeping dog lay! It’s too easy to overthink these things. 👍
5th Jan 2019 11:17 pm
DaveJLBI
Member Since: 07 Mar 2014
Location: Clare
Posts: 661
Hey there, just revisiting this thread.
I have a new (to me) D4HSE (MY2014 facelift with 60k miles) which has just replaced a D4XE (MY2015) - private sale to get a lower mileage / higher spec vehicle.
Just had the main and stop/start batteries replaced on day of sale as the stop start was failing and main / original battery at end of life. It is exhibiting the same voltage behaviour as above - on a journey it runs at about 12.8 to 13.0, but when I lift off or am cruising / slowing, it rises to 14.7ish. Yesterday morning on the first journey of the day (20mins) it stayed at higher voltages but then dropped to lower running voltages.
When not running, it is at 12.6. Voltages are being measured on cheap voltage cig lighter type unit.
Gareth refers to smart charging capability, but on my previous MY2015 it seemed to run near enough to a constant 14.5V, although I only owned that vehicle from 63k miles to 98k miles
Question - is it normal for voltage to raising and lowering?
It will raise when you ease off the accelerator and drop when you accelerate.
16th Mar 2020 7:06 pm
DaveJLBI
Member Since: 07 Mar 2014
Location: Clare
Posts: 661
It does that alright. Watched it a little today. First journey of 25 mins it stayed up at 14.8V and then on next few journeys it hovered between 12.4V and 12.8V when driving but rose when lifting off or breaking.
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