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Trying to work out if the alernator or starter motor are on the way out?
Our Punto struggles to start from cold quite a lot, turns over slowly initially. In the winter on the coldest day it wouldn't turn over at all, but that's the only time it hasn't started. I fitted a new battery last summer with 4 year warranty.
On the way to the MOT the other day after the usual struggling start and a 25 mins run it wouldn't restart, never done that before. Normally turns over much quicker after a run.
This morning put the meter on battery and it was 12.6V and running was 13.8V.
Do these figures sound ok or is it time for a new alternator or should I test over a longer period than the 20 seconds or so I did to make sure?
Or is the starter motor on the way out....
Cheers if you can help me out.
Not a mechanic but 13.8v sounds within range for an ok alternator. Does the starter get slower as you struggle to start it, or just turn slowly at the same rate.
my guess would be starter motor in the first instance
Your readings show a charged battery and working alternator. Tired starter or corroded loose or damaged earth connections could cause the slow turn over and non starting.
Check the earth connection to the starter motor carefully, it will probably be attached to the gearbox housing and an inside chassis leg - if this earth is corroded it will create a current drain and may lead to poor turnover, or like you say it may just turn out to be a poorly starter motor - i doubt it is the alternator.
Start by cleaning all the connections.. probably a bad contact
Clean the battery terminals before anything else, then earth leads, then leads to the starter motor. The get back to us.
check the battery terminal voltage under the following conditions, after driving the car for at least 30 min:
1) At idle, min electrical load (ie, everything electrical off that can be turned off)
2) At fast idle (hold engine at 2500rpm for 30sec) min elec load
3) At idle, max electrical load (turn on everything you can, lights, heated screens/seats, fans etc etc)
4) at idle after 3min with max elect load (same as 3) but wait for 3 mins before taking reading
5) at fast idle, max electrical load
6) at fast idle, max elect load, after 3min
Do those tests and post up the results!
Not so sure, 13.8 volts sounds on the low side of the acceptance band to me. I'd like the reading to be in the 14's. Switch on all your electrics, lights, full beam, blower, heated windows and mirrors, a/c, everything you can and if you've still got 12.5v minimum you're in the clear.
13.8 is as close to perfect as a multi-meter is accurate.
What everyone else has said and you can check for poor earth's by connecting a jump lead from the -ve battery terminal to the starter (or bit of engine/gearbox if the starter is hidden) and see if it turns over faster.
Thanks guys will try those suggestions over next couple of days.
What everyone else has said and you can check for poor earth's by connecting a jump lead from the -ve battery terminal to the starter (or bit of engine/gearbox if the starter is hidden) and see if it turns over faster.
Make sure its not in gear 😉
My standard response is what MikeG said. Creates a temporary earth...you only need one jump lead. Connect negative battery terminal to engine block.
The other test is to grab the negative lead on the battery, and give both ends a firm yank. If it breaks off, you've found your problem (but will have properly broken down until you fix it!)
I'd prefer to see 14.5 volts across the battery with the engine running.
Starter motor.
My Megane did this in January. Sluggish to turn over in the mornings, I thought it was the battery, so bought a new one, and it turned over just as slowly.
Changed the starter motor, and it whizzed round.
I wasnt too annoyed at having changed the battery for no reason, it was the original at 7 years old, so the obvious thing to go wrong.