how do i

username · Post by **username** » Sat Dec 08, 2007 9:45 am

use a multimeter to check if my altenator works?
i've put 3 different batteries in my car and they've all gone flat.
i had the altenator replaced may this year so i was thinking it shouldnt have carked it by now...

any help appreciated

cheers

Gannon · Post by **Gannon** » Sat Dec 08, 2007 10:33 am

Multimeter leads to positive and negative posts of battery
Multimeter set on DC volts.

With engine off, battery should read between 11.5 and 12.5v
With engine running, it should read about 14.5 volts if it is charging propperly, slightly less if you have your lights/other electrical load on.

Test it and report back

username · Post by **username** » Sat Dec 08, 2007 11:26 am

with a freshly charged battery so it would start

OFF = 13v

On = 13v

it was brand new in may because the other one stopped working. what is causing them to die?

Gannon · Post by **Gannon** » Sat Dec 08, 2007 1:23 pm

so it was 13v before you started the engine, and then 13v while the engine was running.

Sounds like its not charging. Is the charge light in your dash on when the car is running?

Possiably a dud alternator

username · Post by **username** » Sat Dec 08, 2007 3:28 pm

Cheers Suparoo.

Matatak · Post by **Matatak** » Sat Dec 08, 2007 3:45 pm

to me if it wasnt chargin..then after a couple of starts it wuldnt start nemore..if ya no wt i mean.

it sounds liek its charging not much btu still actually chargin otherwise ur car wuld eventually die while ur driving. and the volts wuld be going doin every time u start her up and even when u have her stittin

username · Post by **username** » Sat Dec 08, 2007 5:28 pm

Yeah is starts a couple times then not anymore. Then yesterday it was idoling in my driveway and just stopped...

So yeah altenator.

Lucky i got 12 months warranty, $200 brand new.

Rang up Rising Sun today and some bloke called Ben was there and said to ring back monday when Steve was in. The good news is i need to get my car to the insurance place on monday because some dopey lady 'didnt see me there' and consequently reversed into me, all while somehow getting to work on time.

Monday's gonna be fun.

Gannon · Post by **Gannon** » Sat Dec 08, 2007 7:24 pm

Just out of curiousity, does your charge light come on?

Post by **Alex** » Sat Dec 08, 2007 8:07 pm

thats a good point...if the alternator dies, all the warning lights should come on.

edit: silly question, are the battery terminals on tight?

alex

Gannon · Post by **Gannon** » Sat Dec 08, 2007 8:49 pm

the reason i ask is because sometimes the 'charge light' forms part of the field wiring for the alternator, so if the charge light blows, your alternator wont charge.

username · Post by **username** » Sun Dec 09, 2007 4:56 pm

yeah the battery terminals are on tight

and

the charge light doesnt come on... is there a fuse?

Gannon · Post by **Gannon** » Sun Dec 09, 2007 6:22 pm

A fuseible link for the alternator power cable.

Does the 'charge light' come on before you start the car, ie. when the key is in the 'on' position but engine not running. If if doesnt....

Pull off the dash surround and check the bulb. The black piece that goes around the instrument cluster.

I'll have to pull out my wiring diagrams for you

subanator · Post by **subanator** » Sun Dec 09, 2007 11:52 pm

Alt theory 101 - Charge Light come on via the star point of the diode rectifier assembly, and a faulty diode will pass to ground via the light wiring.

Alternators also have a regulator and rectifier in the back of them and can be a combination of things to fail, but not easy to fix.

username · Post by **username** » Mon Dec 17, 2007 5:38 pm

*Takes car to Steve from Rising Sun*

It was the dash lights that was causing the altenator to not charge. The globe for the charge light was fine but some where in the loom the wiring was sketchy so the globe had 12 volts at both ends and for that reason the altenator didnt have its reference voltage and couldn't charge properly. He just wired around everything and it worked a treat.