General Stop/Start not working

[Johnrambo18]

Starting point has got to be checking the battery open circuit voltage. So, after a reasonable run, say half an hour, to charge the battery, let the car stand for a couple of hours to let the surface charge dissipate from the plates. You can achieve a similar effect by turning the headlights on for 5 to 10 minutes if you're in a hurry but many modern vehicles won't let heavy loads - head lights, rear screen heater, etc - be turned on unless the engine is running. Then, without starting the engine or turning any electrical load on, check the battery voltage with a voltmeter/multimeter. If you decide to do this then post the result on here and we'll all have a think about the result.

Like Baglady, If I'm in a car with stop/start I turn it off every time I start up in sympathy with the starter motor/battery/flywheel ring gear/avoiding localized boiling of coolant/turbo/and other stuff which doesn't come to mind at the moment. So, for me, I take failure of the stop/start as an early warning to check battery condition and if that's ok then the the fact stop/start isn't kicking in is a bonus!

EDIT Just because it's such a commonly reported failure, I'd have a quick look at the gearbox earth strap (under the battery box) for evidence of rot, but it's unlikely to be the problem if the engine is starting normally and the car is working well in all other respects. You could also try your local Halfords and ask if they'll do a free battery condition check for you - ours is happy to do this. This procedure is very quick and involves using a battery condition analyser to check the battery's internal cell resistance. The result gives you a much better idea of the battery condition than any simple test you can do at home - unless you have a condition analyser yourself?

Here's the "DIY" one Gendan does in case anyone is interested: https://www.gendan.co.uk/product_FXBT100.html And just to show I'm not biased, another that interests me greatly is the Topdon BT 200: https://www.topdon.com/products/battery-tester-bt200

Latest in stop/start saga. The car is otherwise fine, so I thought I'd wait until service is due. It has now been in for this, and the dealer is supposed to have investigated the s/s issue. All they seem to have done is charged the battery, telling me it is now fully charged and should be ok. But it is no different. I wondered about getting a battery tester for about £20 to put my mind at ease. What do people think?

 

[jrkitching]

I wondered about getting a battery tester for about £20 to put my mind at ease

A £20 battery tester isn't going to be up to the job of telling you whether your battery is up to scratch.

I've said before that the gold standard test of a battery is to put it into a S/S Fiat and see if the S/S still works - and I'm only half joking!

If you've bought a secondhand 500 and are having intermittent issues with S/S not working correctly, just spending £80-£100 on a new battery is pragmatically probably easier than trying to convince the dealer that sold you the car that there's anything wrong with the battery it was sold with.

Used cars often sit for some time in lots, which does the battery no good at all unless it's regularly charged, and most used car dealers don't bother. I would always budget for a battery replacement when buying a used or preregistered car .

 

[Johnrambo18]

A £20 battery tester isn't going to be up to the job of telling you whether your battery is up to scratch.

I've said before that the gold standard test of a battery is to put it into a S/S Fiat and see if the S/S still works - and I'm only half joking!

If you've bought a secondhand 500 and are having intermittent issues with S/S not working correctly, just spending £80-£100 on a new battery is pragmatically probably easier than trying to convince the dealer that sold you the car that there's anything wrong with the battery it was sold with.

Used cars often sit for some time in lots, which does the battery no good at all unless it's regularly charged, and most used car dealers don't bother. I would always budget for a battery replacement when buying a used or preregistered car .

Maybe worth considering a battery. The car was pre registered but only had delivery mileage so the issue of sitting uncharged is possible. It's a bit annoying but I don't know if I want the hassle of keep going back to the dealer..

 

[jrkitching]

The car was pre registered but only had delivery mileage so the issue of sitting uncharged is possible

Might be worth trying to find out how long it had been sitting between manufacture and sale. Most of the component parts (including the battery) will have date codes or stamps.

 

[Pugglt Auld Jock]

Maybe worth considering a battery. The car was pre registered but only had delivery mileage so the issue of sitting uncharged is possible. It's a bit annoying but I don't know if I want the hassle of keep going back to the dealer..

Our new Skoda Scala was a prereg actually registered end of 2023 but delivered to me last day of Feb 2024 with 9 miles on the clock. I'd guess she has been in store somewhere without being run until then. Stop Start didn't work for best part of the first week of my ownership then suddenly started working. Now it doesn't work for about the first couple of miles after startup but then kicks in for the rest of the journey. If the car is left without starting for a day and a half to two days, which happens quite often with us being now retired, and I check battery voltage after that time it shows about 12.3 to 12.4 volts which is ok but not brilliant. I've reported it to the supplying dealer - with whom I have a 2 year service package - but was not enthusiastically received. I don't think the'll do anything unless it fails to start. I won't be surprised if a battery is required in the future (probably just when she's out of warranty!) Must say it doesn't worry me because I cancel stop/start and lane assist on every startup.

If I was a betting man, and knowing these wee FIATs are renowned for it, I'd be confidently betting a new battery will solve your stop/start woes.

 

[The Panda Nut]

I'm wondering if the energy used to recharge the battery, after a stop/start, is greater than the energy saved stopping it for 30 seconds (or however long the short delay is) ?

A few years ago I had a Renault Laguna 2.2dtr. I decided to see of switching off whenever stationary made a difference. It made a staggering 6mpg improvement, so there is at least potential to save. My experiments however suggested that you needed to be switched off for 20 seconds or more before the payback was this good. My stop start has been totally reliable for nearly 6 years but after the car was left for 2 weeks while were on holiday it has become a little reticent. I will probably change the battery if we get any cold weather as there are other signs of its aging like reduced number of bars showing on the charager when connected. It still spins up fine but its probably starting to slide into oblivion and I am not getting caught out for the cost of a battery. If it gets to 6 years old I shall still feel a little short changed. The Seat Managed 12 years. I need to find out the change procedure to reset the battery sensor. I suspect the car may still think it has an old batery if this is not done correctly?

 

[Piccolo Nero e Bella]

Might be worth trying to find out how long it had been sitting between manufacture and sale. Most of the component parts (including the battery) will have date codes or stamps.

I had exactly this problem with S/S when my car was new - hounding the dealer (with information gleaned from this forum!) finally resulted in them replacing the faulty battery, after twelve months, and the issues with S/S disappeared. Be warned though, they fitted a standard battery instead of the proper EFB. I didn't know the difference back then. However, it worked faultlessly for three years till I had the EFB fitted. That one's still in the car and the S/S works to spec (when I choose to switch it on!).

The compliance plate in the boot tells me my car was built 10/12, but it was first registered nearly ten months later, 07/13, with only 4 miles up!