alternator issues

Let me 1st say this is a great forum and I have lurked for quite awhile and have found many helpful tips here (this site saved my a lot $ about 6 months ago when the dealership told me I had a bad torque converter and need transmission replaced. I was able to follow a write up on a transmission flush and it solved my problem). I have a 2008 Double Cab 4.0L with 153k miles. Earlier this week it developed a whine from the engine compartment. I had it narrowed down to either the power steering or the alternator. This morning while backing out of my driveway, I reached down and turned on my a/c and the noise stopped. About 2 miles down the road I noticed my battery light come on and it hadn't been on before. Is there anything else it could possibly be besides the alternator? I don't have a lot of time in trying to get this fixed and just wanted any advice that any of you may have. I'm thinking I should go ahead and buy an alternator and install over the weekend and that will take care of my problem.

Don't know if this may have caused it but trying to connect the dots. Last Saturday I cleaned the seats and interior. I parked the truck in the garage overnight with the doors open so it could dry. I turned the overhead light off and keys were not in the ignition. Can't remember if I drove the truck on Sunday but the noise started on Monday just sitting at a red light. So I don't know if this could have anything to do with it. Battery is only a 1yr old and I haven't had any problems starting the vehicle or any signs the battery is going bad. Any advice would be appreciated. I am by no means mechanically inclined but with Tacoma World and you tube I'm not afraid to tackle what some may consider an easy task.

 

It is easy to do a basic alternator check.

Crank the truck, turn on the lights, and apply a voltmeter to the battery. 12.5 volts or so, alternator is bad, 13.5 and up, alternator is at least working. If the voltage drops below 12.5 as you add A/C and such, looks like an alt problem. Just don't forget the lights. These things often fail where they will produce 14.5 volts, but hardly any amperage. So you need something to suck up enough amperage to make sure the alternator is doing what it is supposed to do.

Note that there are fuses in the circuit as well, so a short somewhere could blow a fuse and prevent the alternator from charging the battery, so you might have to test further, such as measuring the voltage output of the alt. If it shows 14.5, but the battery is stuck at 12.5, something is open between the two. Some use a big fuse in the engine bay fuse block. Some use a fusible link. Some use a big inline fuse that is hidden. Not sure what Toyota does, if anything there.

I found this on a Ford once where a friend bought a battery that was the wrong type but right size (+ and - posts were reversed). He didn't know any better and hooked it right up. Blew a BUNCH of fuses, including the alt fusible link, but didn't damage any electronics somehow.

 

Thanks for the reply Robert. Was able to nail down that it was my alternator. Got it replaced today in pretty quick time. Thanks to TW I was able to save some money by replacing it myself. I wouldn't have the confidence to even attempt something like this without this website. I have never been good with tools. I once bought a grill as a wedding gift for my best friend. The day they were to return from their honeymoon I went over and was going to put it together and leave it on the porch. 6 hours and a 12pk of Bud later I still didn't have it together. My friend gets home and has it complete in 5 min. Needless to say I'm a little pumped over my accomplishment today. Thanks again TW!!!!