Battery problem? Or Alternator?

[Torquemonster]

I think your throttle body needs cleaning.

[Itnato]

No it doesn't really change. It just hovers thereabout 12.8V

 

its not right. W/o cranking, it shd alrdy read at least 12.

w engine running, it shd be alrdy 14+.

[Gasguzzler]

Sounds more like ignition or fuel problem since u have no problem restarting the car.

 

Check your spark plugs, fuel injectors and fuel filter?

[Matrixx]

Went to a workshop this morning to check on the battery and alternator, and both turns out to be healthy. Apparently the voltage gauge in the car isn't accurate because a direct measurement using a multimeter shows the voltage to be about 13.5V when car is running.

[Weihui]

Did your batt indicator light up or flash intermittent when the car vibrates?

 

If it flashes, chances are your alternator worn out.

 

If it doesn't, can ask Mazda to adjust your idling speed on your car computer.

 

Crank start is done by starter motor, has nothing to do with alternator.

[Matrixx]

Did your batt indicator light up or flash intermittent when the car vibrates?

 

If it flashes, chances are your alternator worn out.

 

If it doesn't, can ask Mazda to adjust your idling speed on your car computer.

 

Crank start is done by starter motor, has nothing to do with alternator.

 

Nope, battery indicator didn't light up of flash. No CEL either. Beginning to wonder if it's the MAF sensor. But I do clean it from time to time though.

[Alphas]

My car was having intermittent cranking problem and battery light, and went to have my car checked at autosaver. The mechanic took a meter and connect to the battery terminals. It reads 12.4V idle and told me the alternator is spoilt. Good alternator should read above 13v and want me to replace it.

I asked him he should connect DIRECTLY to the alternator terminals and not the battery terminals since there could be electrical issues. He told me if the alternator is working they will replace back the alternator. I argue with him why should I change a new alternator if my current one is alright. This waste my time and not fix the problem.

Appalled by them i went back home to do a voltage drop test with my multimeter. Connecting to the battery negative terminal and the car chassis when idle, my multimeter read 300mV drop. It is an electrical problem (the voltage drop must be below 100mV), and also check the battery positive terminal by connecting to the alternator fuse in the fuse box and read only 50mV(the voltage drop must be below 100mV). So there was a bad connection in the negative electrical terminal.

I drove to Kian Teong Auto centre #01-08 at Sin Ming autocare. I told them to check the alternator and the mechanic took the meter and connected DIRECTLY to the alternator terminals, FINALLY someone who know how to check alternator! The reading is 13.5V and told me the alternator works great and he needs time to find the electrical issue. I came back in 2 hrs and he replace the negative battery terminal and wiring.

If you didnt read the whole text, it is simply DO not condemn the alternator immediately, always assume there is electrical issue before changing it. Do a simple voltage drop test above and connect directly to the alternator terminals to check voltage. You could end up spending $500-900 for nothing than a $50 battery terminal issue.