I took my second car - a 2014 Škoda Superb estate - to Bristol & back for a work meeting.

It is fitted with an aftermarket Head Up Display - which means I've been looking at this display for 400-odd miles...

So - here's the question. You can see that it's idling, and the voltmeter is showing 11.8 volts. It has been reading similarly for the entire trip, with the occasional foray to just over 12 volts. The rpm doesn't seem to make much difference, although there did seem to be an increase in the voltage when electrical load was increased (lights; fan blower etc).

I'm pretty sure that it generally showed 13–14 volts when I've been driving it. 🤔

Has my memory failed me? I've not been using it much lately, as the convertible has been out during the good weather.

Might this be an indication that the alternator is on its way out? The car starts easily and there's no alternator light appearing on the dash. 

The car as 82k miles on, and had a new battery in 2023. Even after the long distances I have covered in it over the last couple of days, the Stop/Start mechanism has not kicked in.

Any advice appreciated. If you are really miffed at me asking, you can pretend it's an Audi A6 Avant...😆

Cheers,

Mike 😎

 

 

 

Best thing to do is get a diagnostic check to see if any fault codes flag up or get an auto electrician to take a look

Hello Mike,

Yes alternator output should be around 14.5 v. Suggest you get it checked and expect a failed diode or similar. If it were mine, I would simply get yours repaired, since new alternators can be of rather poor quality.

Low alternator output/ low battery voltage will result in the S/s system shutting down, so there is at least a positive here if this engineering averse system isn’t working! 
Regards,

Gareth. 

Thanks for the replies 👍

I'm about to go away for a fortnight or so and - despite Gareth's advice about new alternators - will likely buy a new one and have it swapped. I'll then get a voltage regulator for the old one and keep it as a spare.

Mike 😎

 

PS I'll post the results up here when done...

That’s fine Mike,

Where are you going to buy a new alternator from?

Regards, 

Gareth. 

Probably one of the Usual Suspects: ECP, GSF, eBay - a brief search revealed this for £218 delivered.

I'll do a good search before ordering. I like to think that a manufacturer like Bosch should be a fair sign of quality (although I don't know what's actually fitted to the car at present, and it's a job to get to see). Certainly not something I want to do before flying on Monday... 😆

Mike😎 

I have dealt with Parts in Motion for number of years, and I find their prices are competitive, and their service has been faultless. 
Yes, you should expect Bosch to give you good service - make sure you order by 2/9 to get a remarkable 20% of the quoted price. 
Exchange item,where you have to return your existing one??

Please let us know how you get on. 

Yep - I think I'm going to buy that now - it brings the price down to just under £175 delivered. I'll get it sent to my mate's house, since I'll be away.

It being an exchange item puts the kibosh on my plan to repair and keep the other as a spare, but that's acceptable, given the price... 🙂

Mike 😎

So - I got the car back from the garage yesterday, with a new Bosch alternator, plus belt and tensioner fitted (it's a pig for access, so it makes sense to do the extras while you're in there).

Result? Not what I'd hoped... ☹️

The volts never drop below 12, but tend to be in the 12.8-13.0v range. By way of contrast, my A4 displays 14.7v on average.

Is this liveable (ie, not going to drain the battery)? If not, where should my next stop be? 

I don't have to tell the car it's got a new alternator (like I do with a new battery), do I?

Cheers,
Mike 

 

 

 

1 hour ago, gsmdo said:

I don't have to tell the car it's got a new alternator (like I do with a new battery), do I?

It was necessary I would expect a decent garage to have done it. It wouldn't hurt to phone the garage and ask.

Edited September 25, 2025Sep 25 by cliffcoggin
correction

So — an update.

Took the car for a 40-odd mile round trip today. On the outbound leg, the voltage never dropped below 12, and was generally in the 12.8-13v range. The Stop/Start actually worked when I stopped at temporary traffic lights.

On the way back, however, the voltage rarely reached 12v — mostly around 11.4-11.8v. When stopped at the same lights, the Stop/Start didn't operate.

So, basically, fitting the alternator hasn't solved the problem. 

I plugged my Carly device in this evening, and it found no faults or codes in the electrical system, other than the fact that I have a non-standard stereo fitted and non-standard indicators in the door mirrors. 

It did find a possible fault in the Haldex switch in the 4WD system, though — oh joy… 

So, my next step will be to find an auto electrician and ask them to look at it… 

Mike 🙄

 

2 hours ago, gsmdo said:

 

So, my next step will be to find an auto electrician and ask them to look at it… 

 

 A good decision. Did you phone the garage?

21 hours ago, cliffcoggin said:

 A good decision. Did you phone the garage?

Popped in to see them. They weren't aware of any action needed to tell the car there was a new alternator. Nothing came up on my Carly scan, either...

I've emailed a local mobile auto-electrician to ask for him to look at it. I'll report back once he's been...

Mike 😎