Bad Alternator?

[trailshredder]

Driving the Q home last night, almost home, headlights and dash lights all of a sudden dimmed, airbag light started flashing. I am guessing alternator but confused why the charge/bat light didn't come on. Thoughts?

[sstroudwku]

The AC current the alternator produces before converting could be rippling, when it does it can effect things like that. So it may be putting 14v out, but the ripple can screw things up.

[Skibane]

When mine started to die, it didn't turn the charge/bat light on. Apparently, only certain faults in the charging system will turn the light on.

If you've got a digital test meter (or "DMM"), you can use it to test your alternator by measuring the battery voltage with the engine idling and the headlights on. A good alternator will keep the battery voltage in the high 13's to low 14's. An alternator that's limping along will have trouble hitting 13 unless the engine is revved. A dead alternator will allow the battery voltage to sag below 12.7.

The AC current the alternator produces before converting could be rippling, when it does it can effect things like that.

Mine developed a very noticeable whine that varied with engine speed, due to one or more diodes failing in it. Dead diode = no DC current being produced at some point during every revolution the alternator made, so there was a huge amount of ripple present.

Since the battery is what filters out the normal amount of DC ripple produced by a healthy alternator, having a lot of extra ripple is also hard on the battery.

[elwesso]

If you're not sure, I'd just take the car to Advance/Autozone/O'reilly or something similar, they have a tester and they'll test your battery and charging system for free... Bad batteries and bad alternators can cause funky things, so if nothing else it's good to know that (best case) everything there is good.

[trailshredder]

Pulled it off last night, getting ready to take it to Advanced. Battery is brand new so I am leaning toward a bad Alternator. It has been whining a lot lately. I'll post back test results.

[elwesso]

Cheap rebuilt alternators tend to not be so good. I'd be leery of using an auto parts store rebuilt unit, especially considering the alternator replacement isn't exactly a walk in the park.

[trailshredder]

Alternator tested bad, dead actually! Ordered a new one online.

[Skibane]

Cheap rebuilt alternators tend to not be so good. I'd be leery of using an auto parts store rebuilt unit, especially considering the alternator replacement isn't exactly a walk in the park.

+1.

The only exception I'll make to this rule is for Car Quest stuff - They seem to do decent rebuilt electrics. The replacement I bought there was actually remaned and warranteed by Hitachi.

[Q451990]

Ditto on buying a good one. Real Hitachi rebuild - not a cheap replica in a worn Hitachi box out of some guy's closet in Atlanta (Yeah, I did that ) or OEM only. These things are such a beiotch to get back in you don't want to do it twice!

Heath

[maxnix]

Cheap rebuilt alternators tend to not be so good. I'd be leery of using an auto parts store rebuilt unit, especially considering the alternator replacement isn't exactly a walk in the park.

+1.

The only exception I'll make to this rule is for Car Quest stuff - They seem to do decent rebuilt electrics. The replacement I bought there was actually remaned and warranteed by Hitachi.

Bought a new Hitachi a couple of years ago. Still going strong.