Battery, alternator or starter motor?

longwalks1

Drove home from work yesterday (5 miles) and when I started it, it took a couple of turns to start. Sure as ever, this morning it didn’t turn over at all and I needed a jump start to get it started.  Currently have it on charge.

How can you tell what’s at fault please?  What simple tests can I do to determine if it’s the battery that’s knackered, or the alternator, or the starter motor? 

Thank you everyone in advance 

roddydogs

Well, how old is the car and battery? If battery's more than 5years old its probably the battery. But always get the charging checked out, not really a diy job.

oldagetraveller1

If it's turning over and starts when charged or jumped that would possibly rule out the starter motor.

Goudy

Short tripping (5 miles) and the cold weather has probably killed off your battery if it jump starts, as Oldagetraveller states, the starter motor appears to work ok when the battery is jumped.

With a voltmeter you can gauge the alternator output.
With the car is running, set the meter to read volts and check the reading at the battery terminals.
An alternator in decent condition should put out 14.4 volts to the battery.

But while you have the bonnet up, check the belt the runs the alternator.
If it's missing, loose or cracked and crispy, you'll want to replace it so you get a good reading at the battery.

It's harder to test a battery, ok a multimeter can test for volts (12.6 ish is about right with the engine off) but you need more than volts to start an engine, you also need amps and there are special tools to test batteries for amps. 
A battery can still read 12 or so volts but have little amps, particularly when they get old as the plates inside get coated with sulfate crystals from the sulfuric acid.

greyteam1959

Take your car to your local independent garage & get them to test the battery.
Not really a DIY job to do a load test on a battery.