Looking for some guidance. I'll try to keep this short. Leading up the the suspected alternator failure I have noticed a few things. My keyless entry was very sluggish if working at all. Naturally suspected the fob battery, but still sluggish after replacing that. Then last week rolling down the road my (aftermarket) CD player just quit out of nowhere. I didn't notice anything else until the next morning when the car wouldn't start.

From there I suspected my battery was shot, as it was only reading ~8V. I jumped the battery and went to Auto Zone to buy a new battery. The salesman said let'* go out and test it first. After a 10 minute drive the battery was now reading ~12V with the engine off. He asked me to start the vehicle, and it started no issue. Now the alternator was only putting out ~7V. He said my alternator had failed. That would make sense, seeing that I was slowly losing power for my accessories and the eventual failed start.

My question is if the alternator had failed, then how was my battery now reading 12V after a 10 minute drive? What am I missing? After driving there I have started it up with no issue 4-5 times. The CD player still doesn't work though? What voltage does the starter need to see before starting the engine? There is no hesitation, it fires right up like normal. Either way, I trusted his suggestion and purchased a new alternator, which I plan to R/R myself. It seems pretty straight forward, but I had some questions there as well. This is how I plan to attack it, please correct me if I'm forgetting anything.

1. Disconnect negative lead on main battery
2. Remove various intake pieces to gain better access
3. Get a socket on the belt tensioner (above the large pulley that I'm assuming is just the drive pulley off of the crank.)
4. Slip the belt away from the alternator drive.
5. Remove 3 mounting bolts
6. Remove wiring.
7. Reverse cycle

I'm pretty sure all of this will be metric, which sucks because I only have SAE tools. But anyway, looking for some advice from the pros. Hopefully the diagnosis of the alternator is accurate to start. Then any suggestions on the R/R would be appreciated. I used to do airline maintenance, so no stranger to changing out generators, etc... but I have never worked on cars, so feeling a bit in the dark with no manuals.

Thanks!

I don't know how much room you have in the front of the engine, but your list seems accurate enough.

It would help if we knew what kind of car you have. Here is the procedure for a 2010 Malibu:



Removing the Old Alternator

1. 
   Disconnect the negative battery cable using a wrench.
   
2. Remove the coolant reservoir for better access, if necessary, using a ratchet and socket. The reservoir is the plastic container located at the front and to the right (passenger side) of the engine compartment.
3. Detach the belt guard from the top of the belt. if your particular Malibu model is equipped with it, using a ratchet and socket. The belt guard is located between the water pump and the power steering pump.
4. Rotate the belt tensioner pulley to release the belt tension. Use a long 13 mm box wrench or 3/8-inch drive breaker bar, depending on your particular model.
5. Slip the belt off the alternator pulley.
6. Remove the two top alternator mounting bolts and the front bolt if you have a 2.4L engine model. Remove the top and front mounting bolts from the alternator if you have a 3.1L engine model. Use a ratchet and socket for both model types.
7. Unscrew the mounting nut from the rear of the alternator if you have a 3.1L engine model. Use a ratchet with a ratchet extension, universal joint and deep well socket to reach the mounting nut.
8. Unplug the electrical connector from the alternator. Then detach the wire from the back of the alternator using a wrench.
9. Unscrew the power steering line clip using a ratchet and socket, if you have a 3.1L engine model, so that you can work the alternator out of the engine compartment.
10. Remove the alternator from the vehicle.

Installing the New Alternator

1. Set the new alternator in its mounting position in the engine compartment.
2. Install the power steering line clip, if you have a 3.1L engine model, using the ratchet and socket.
3. Plug the electrical wire harness and the single wire with the retaining nut into the back of the alternator using the wrench.
4. Install the mounting nut to the rear of the alternator, if you have a 3.1L engine model. Use the ratchet with the ratchet extension, universal joint and deep well socket to tighten the mounting nut.
5. Install the two top alternator mounting bolts and the front bolt if you have a 2.4L engine model. Install the top and front mounting bolts to the alternator if you have a 3.1L engine model. For both models, use a ratchet and socket.
6. Rotate the belt tensioner pulley using the long 13 mm box wrench or 3/8-inch drive breaker bar, depending on your particular model.
7. Slip the belt onto the alternator pulley.
8. Attach the belt guard to the top of the belt, if your particular Malibu model is equipped with it, using the ratchet and socket.
9. Install the coolant reservoir, if you had to remove it, using a ratchet and socket.
10. Connect the negative battery cable using the wrench.

My guess would be that he owns a '10 Malibu with the 2.4 engine...

Yes, sorry about that. I drive a 2010 Malibu 1LT as suspected. What is crazy though, is that everything is now working completely as it should. Can an alternator be intermittent or do they usually hard fail? The only thing I am still noticing is that the keyless entry is very sluggish. Not sure if that is related to my alternator/charging issue at all.

Maybe I should expand on that a bit. I went out to the car, it had been sitting for 2-3 days. Read battery voltage at 12.3V. Started the car, and immediately noticed that now the CD player was working. Took another reading across the battery while running, and reads 14.3V. Assuming that reading is coming right off the alternator? I've driven to work and back the last two days with no issues. The alternator is due to arrive tomorrow, I hate to return it for a refund knowing that the alternator may be on it'* way out.