this is a bad alternator, right?

[surfstar]

okay, saturday morning out running some errands, and i start my car in the store lot and notice my charge indicator light and my rear brake light indicator lights are on. rear brake lights are all fine. other thing i notice driving home is that my temp gauge is only half as high as it should be ???. check all my belts (only 1.5 months old) and they're fine, alternator is spinning, not making weird noises. temp seems normal as the cooling fan will kick on, although the gauge reads low - i'm assuming the gauge isn't getting enough voltage to read correctly.

tried wiggling battery connections, engine grounds, fuses, same problem. pull the neg battery cable while the engine is idling and it dies. try again with engine held at 2k RPMs, same thing. so it looks like the alternator, right? can't really get a voltage tester on it, where its located, very easily. anything else it could be?
car is a 1993 mazda mx6 2.0L MTX w/ 175k miles.

thanks

 

[brianl703]

Disconnecting the battery cable with the engine running can damage your electrical system. I also don't think that it's a good test of the electrical system because the battery acts as a filter, smoothing out the voltage from the alternator.

Better would be to use a multimeter connected to the battery, or the cigarette lighter socket if you can't get to the battery, or between any fuse and a ground..for the purposes of checking proper alternator output, it isn't necessary to test the voltage at the battery.

 

[Jim 5]

I just had the exact same issue on my truck at 170k miles. You have the classic symptoms of a failed alternator and at that mileage, your alternator doesn't owe you anything.

Pull the alternator out of the car and take it to your local autozone or checker auto parts type place. They will test its output for you.

I got a replacement/remanufactured alternator at this type of auto parts store with a 5 year warranty. So long as the replacement alternator dies in less than 5 years, I get a replacement...and the 5 year clock starts ticking again. That could mean a new one for the rest of the life of the truck!

 

[surfstar]

called the Mazda dealership - $570 $350 for the OEM alternator.
called Pep Boys $139.99 for lifetime warrantied alternator, $78 to install.

thats cheap enough for me to not take time off work to replace it myself. I don't think they know all of what's involved to replace it - remove a crossmember and unbolt an exhaust section to gain access to drop it - but they said they will stick to the flat rate if they go over.

 

[surfstar]

it does seem like its the alternator for sure after reading around online. also found out, as stated by brianl703, that disconnecting the battery isn't good for today's cars - it was fine on my '68. oh well.