Alternator Good or Bad?

[Howy]

Evening Gents,Maybe something or nothing,started the motor today,battery voltage shot to 15v,driving from cold went down to 14.5/6 volts and now seems settled,this was done on the dic.Any thoughts,thought the voltage reg maybe on the way out?

[Howy]

#Bump#

[LondonsFinest009]

Evening Gents,Maybe something or nothing,started the motor today,battery voltage shot to 15v,driving from cold went down to 14.5/6 volts and now seems settled,this was done on the dic.Any thoughts,thought the voltage reg maybe on the way out?

mine normally jumps to 15v until I start to drive then drops to about 14.5v and stays there.

never bothered me and always thought it was normal.

first noticed it on a 12v usb socket with the display and it corresponded with my OBD scan app.

[LondonsFinest009]

Sooo Sod’s law for me really, on the way to work it shot upto 15v from cold, started driving and it dropped to 14.5 then as I was driving it crept to 15v and stayed there the entire journey.

first noticed 15v last September on my way to Devon and it’s started on the button every time since.

battery’s showing 12.6v on my multi meter with the engine off.

Is the regulator on its own or built into the alternator?

would be good to know what other members are getting whilst the engines running.

[LondonsFinest009]

Sooo Sod’s law for me really, on the way to work it shot upto 15v from cold, started driving and it dropped to 14.5 then as I was driving it crept to 15v and stayed there the entire journey.

first noticed 15v last September on my way to Devon and it’s started on the button every time since.

battery’s showing 12.6v on my multi meter with the engine off.

Is the regulator on its own or built into the alternator?

would be good to know what other members are getting whilst the engines running.

on my way home it sat happily at 14.4v, maybe take ambient temp into account and overcompensates in the morning when temps near 0.

[Drew]

That's where mine sits, that's with the engine cold..

[Howy]

I'm wondering if these alternators are of the'smart' type and compensate for as said temp etc.I'm having mine checked out on Monday and will post findings and results.

[0011728]

Hi Howy, this may answer your query?

https://workshop-manuals.com/vauxhall/astra-j/engine/engine_electrical/description_and_operation/charging_system_description_and_operation/

[Howy]

Thankyou for that interesting read/info.Looks like my alternator is operating as it should,just not noticed the varying battery voltages before on the dic,will try it again this weekend.Thankyou again.

[peterdw]

Mine (2105 Holden Insignia VXR) has always moved about from around 12V to around 15V - doesn't seem to be a pattern to it; never bothered me. What does irritate me is why the voltage guage only has 4 graduations between 9V and 14V ... 9 + 4 = 13! Did they save money through a 20% reduction in graduation marks between the main numbers?! How many people count in modulo 1.25?

[Howy]

Update,thanks @0011728,confirmed my alternator and charging system is 100% ok,me getting paranoid,the system is behaving as it should

[LondonsFinest009]

Update,thanks @0011728,confirmed my alternator and charging system is 100% ok,me getting paranoid,the system is behaving as it should

just thought to myself, I wonder what happened with this.

that’s good, put my mind at rest about mine now

[Guest]

Is has an type for 'smart generator' yes that adjust the voltage after how much power needed and the state of charge of the battery.

I have a battery monitor in my diagnostic tool, sometimes i see 15v, sometimes 13.7v, depends on how cold it outside and i have driven longear trips or if it has been much 'small' driving with alot of starts and stops.

It also can high the ide rpm upto 1100rpm if the battery is low, and does high the ide rpm when it get's below a surtan temp, i do not remember at what temp thow..

[LondonsFinest009]

Sorry to bring up an old thread..

so I noticed after a 60min drive on the motorway my voltage is sitting at 12.3v whilst the engines running?

in the morning it sits at 14.7v which is normal. Never noticed it drop to 12.3v with the engine on. I’m guessing I’ve got a really smart alternator that doesn’t charge the battery when it doesn’t need to?

or just a bad battery/alternator.

[LondonsFinest009]

Sorry to bring up an old thread..

so I noticed after a 60min drive on the motorway my voltage is sitting at 12.3v whilst the engines running?

in the morning it sits at 14.7v which is normal. Never noticed it drop to 12.3v with the engine on. I’m guessing I’ve got a really smart alternator that doesn’t charge the battery when it doesn’t need to?

or just a bad battery/alternator.

just had it checked, alternators knackered.