A few weeks back I noted when using my Torque Pro that my battery voltage was reading at 12.8-13.2V over the course of my drive. It seemed low but all systems worked OK. I assumed my old smart charger wasn't working correctly and as it was it shorted out so I just got m Ctek MUS 4.3 with battery and alternator tester. Plugged in and it went through it's charge steps and the battery checked out as good. However the alternator test showed the alternator was not charging. So this was the 3rd voltage test method I used and being in denial I didn't want to believe it was the alternator but now I think it is. Funny thing is the battery was replaced in 2013 by the previous owner and I bought it in 2014 so not having a suspicion there was a problem I drove the car and never having a gauge didn't think there was an issue. Maybe the problem existed and because I had the charger on every night it didn't fail. Well I'm under warranty until July and then an additional CPO warranty for 2 more years. Just called the dealer and will take the car up to Albany in 2 weeks to get it resolved. 15,000 miles now on the car. I'll have them check the water pump and the battery while they are in there.

 

I still don't think that anything would be wrong with your alternator. If you are checking it AFTER the car has been sitting with a trickle charger connected, the voltage levels are up and the alternator will not charge.

Disconnect your charger for a few days, or turn on some accessories (Display, lights, AC, entertainment etc) that draw power and then start the car and check the alternator charging. You really do not need a fancy tester, simply look at the voltage and if it is near or just over 14 volts, the alternator is charging.

 

I considered that but it's not the normal way an alternator works. There is a high draw on the battery during start up which will pull the battery down. You would normally see high voltage being put out by the alternator. I don't think I have ever had any of my cars regardless if the battery was new or old that would not go to 13.8-14.2 volts on start. Not knowing this charging system I didn't know if it were so sophisticated that it would reduce alternator output if the battery was fully charged. But in a normal system the alternator runs all of the electrical system and also recharges the battery so you expect to see 13+V all of the time. Here is another sign. With the new Ctek it charges the the battery to 13.7 volts which is the float step. With the battery at 13.7 I start the car and it starts dropping a few tenths at a time and while driving I see it go down to 12 volts and bounces to 12.5. There should be a constant output of the alternator. I also have the Ctek hooked up to the positive terminal of the battery and the negative goes to a ground screw. I'll see in a few weeks.

 

My XKR did exactly the same when I had my Torqe Pro connected. After charging it for weeks with the trickle charger, the voltage dropped all the way down to 11.9 after the initial start up and drive cycle. Following a restart after an hour of time spend somewhere, the charge was the normal 14.1 VDC. That was months ago and I have not checked it since and the car runs, starts fine every time even after being off the charger for 2 weeks in my garage.

Electronics just don't work like the good old systems did years ago...

 

That's the problem my car does not see 14.1V even after running for an hour . If the battery is at 12.8V it doesn't go up after start it stays the same for a while and then starts to drop. The car is running on the battery and not the alternator. I have a 1 1/2 hour drive to my dealer and the Ctek now is on "float" step which is 13.7 V and the battery is only a few years old so my gamble is it shouldn't go lower then 12V on the drive up. Considering I have been taking hour drives with it now it shouldn't be a problem.

 

The water pump is going to FAIL! I have forseen this! When they replace it...make sure its the new italian model and MAKE SURE THEY REPLACE THE STUB PIPE! I AM ON MY SECOND WATER PUMP IN 6 MONTHS

 

I mentioned the WP and they will check to see if it is leaking under the front weep hole. If it is they will replace it. I'll need to see the diagram to understand what the stub pipe is and if it is plastic I'll get it replaced if the WP needs to be done.