voltage...

[CoryM]

Chicken or the egg?
A bad battery can draw down on the alternator keeping it from producing full voltage. Charge the battery (or temporarily replace with a known good one) and check your voltage again. Either way you want to have the battery charged because if you replace the alternator, the new one will overwork itself trying to charge the low battery. It is only meant to top-up the battery, not fully charge it. I would guess it is the battery in this case but hard to tell from several thousand km away ;)

Cheers.

[CTScott]

Originally Posted by CoryM

Chicken or the egg?
A bad battery can draw down on the alternator keeping it from producing full voltage. Charge the battery (or temporarily replace with a known good one) and check your voltage again. Either way you want to have the battery charged because if you replace the alternator, the new one will overwork itself trying to charge the low battery. It is only meant to top-up the battery, not fully charge it. I would guess it is the battery in this case but hard to tell from several thousand km away ;)

Cheers.

For the battery to be bad enough to drag down the output of the alternator, it would also not be able to start the engine.

[CoryM]

Originally Posted by CTScott

For the battery to be bad enough to drag down the output of the alternator, it would also not be able to start the engine.

Little car like the Yaris probably draws >100A so there is still a lot of room to start the car, yet draw the voltage down. Also can be that the battery reserve sucks, but still cranks well (for a short time anyhow). I've seen a few misdiagnosed alternators due to batteries. While it is entirely possible to be an alternator, it's far easier/cheaper for the average guy to charge his battery first and see what happens to his voltage. Especially since he should be doing that before putting a new alternator in anyhow.

Cheers.

[CTScott]

Originally Posted by CoryM

Little car like the Yaris probably draws >100A so there is still a lot of room to start the car, yet draw the voltage down. Also can be that the battery reserve sucks, but still cranks well (for a short time anyhow). I've seen a few misdiagnosed alternators due to batteries. While it is entirely possible to be an alternator, it's far easier/cheaper for the average guy to charge his battery first and see what happens to his voltage. Especially since he should be doing that before putting a new alternator in anyhow.

Cheers.

Agreed that the battery should be verified before going through the expense of replacing the alternator.