battery or alternator?

[burchy1073]

can you test if you are having battery or altenator problems with your deisel engine the same as a petrol engine i.e with engine running take positive lead of battery, if car stalls your alternator is the problem, if it keeps running your battery is the problem

[oncedisturbed]

There is a tester frim super crap for about $15 that does exactly that. Has a - and + poles with led indicators that show charge etc

[growler2058]

My ol gal will just keep on keeping on without a battery in. Dunno about the newer diesels though

[Sir Roofy]

My ol gal will just keep on keeping on without a battery in. Dunno about the newer diesels though

haaaha you have proved that once or twice but you found it hard to start with not much battery
and some dirt where it wasnt spose to be pml

[97_gq_lwb]

Disconnecting the battery whilst the engine is running is a great way to burn out your alternator.
Buy a multimeter they are cheap as chips these days.
http://www.supercheapauto.com.au/online-store/products/Best-Buy-Multimeter-Digital-12V-Automotive.aspx?pid=4405&menuFrom=5029#Description

Heres a how to youtube video gives you an idea
http://www.youtube.com/watch?v=QpG8uQHCDQk

[growler2058]

haaaha you have proved that once or twice but you found it hard to start with not much battery
and some dirt where it wasnt spose to be pml

MMMMMMm correct hahahahhahaha

[Lieney]

As As 97_gQ_LWB states, get a multimeter.
$10 from Dick smith.
Don't disconnect battery while engine is running as current flows when alternator is charging.
Disconnecting battery during engine running can cause a massive voltage spike to travel through the system, blowing alternator, computer or another place it can find to earth.
Same goes for jump-starting a flat vehicle. Disconnection during operation can cause problems.

Vehicle electrical circuit can be tested in the same manner whether Diesel or Petrol.
Battery voltage & condition, alternator and voltage regulartor function can be tested in the following manner.
Ensure battery terminals clean, tight and in good repair, along with cables and all relevant connections. Water level in battery should also be right.
1-Vehicle switched off connect multimeter Neg lead to earth terminal post. Pos multimeter lead to Pos post. (ensure you set multimeter voltage correctly) Voltage should be above 12 (15-ish if AGM electrics from memory so up to 20v should suffice)
2-Turn key and crank engine. Voltage should not drop below 9v. Anything below 9 (as a basic rule) indicates the battery is on its way out and will struggle i winter and need replacing soon.
3-Engine can start and run. Voltage should climb up from 12 to 13.2 (sometimes up to 15v). If not idle up to about 1000rpm.
If there is no increase in voltage, alternator / charging issue is present. Can also check output at B+ terminal at rear of alternator for output voltage.
If increase in voltage to say 13.9, charging circuit is good and alternator is functioning.
Turn headlights on high beam, voltage should remain around same figure.
If the voltage climbs higher with revs, the voltage regulator is faulty
A difference in voltage (electrical pressure) allows current to flow through a conductor (wiring).
So, if the voltage went from 12.2 up to 13.8, this means current is now flowing, thus charging your alternator.
Ensure all connections are serviceable, wiring is connected, battery is full of electrolyte etc etc before you test it.