Alternator or Battery?

[SunnyG]

Hi there, just got me a PD130 A3, car has a strange issue has to be push started otherwise doesn't start can then be driven around but lets say you drive it for 20mins the car doesn't start again. Could this be battery issue or alternator?

 

[jb0o]

Sounds like battery isnt holding its charge.

 

[aragorn]

stick a voltmeter across the battery with the engine off, and again with the engine running.

 

[SunnyG]

What should I be looking for on the voltmeter? I just want to be sure to be honest.

 

[Ste_Nova]

13.9 or above when running

 

[SunnyG]

So if its below it means? sorry about being such a noob

 

[Ste_Nova]

alt not providing charge

 

[SunnyG]

okay thanks so if i see 13.9+ its the battery for sure?

 

[aragorn]

could also be the starter, hence why i said check with the car off too

 

[SunnyG]

okay thank you but i guess if its lower than 13.9 running that eliminates the alternator? Thanks for all the help

 

[aragorn]

if its at or above 13.9 then the alternator is fine.

With the car off i'd expect to see 12.6v or so from a healthy battery.

 

[SunnyG]

thanks for all the help

 

[Squirrelofdoom]

TO be hoenst, if your alternator was gone, you couldn't get a mile down the road before your 12V system shutting off I think you can safely assume your alternator is fine