Yesterday, on way home, convenience feature disabled message came up, shortly followed by the ALTERNATOR/BATTERY warning (VISIT WORKSHOP). Of course, car put itself into the fail-safe setting 1 where it disables things such as AC, seat control, etc. Got the car home and after looking at the aux battery in the car, it looked a few years old so figured Id replace it to start. Went to Advance and bought an Autocraft BS-14 battery (main battery was replaced 2 months ago - Autocraft Gold). After installing the Aux last night, nothing changed. I drove around the block and the error didn’t go away.

Fast forward to this morning (after figuring out how to access car voltage on cluster screen), turned the key to position 1 and UB Voltage was showing 11.7-11.6V (low). After firing the car up on cold start, it went down to 11.2-11.1V. I had 2 errands to run, and after driving the car 15 minutes, it sat for another hour, and then I went to start it and it struggled starting. I then drove it over to a clients shop nearby where we pulled both batteries to throw on the tester and although both tested fine, they were a bit low on juice. Charged both batteries to full in a few hours and went to put them back in the car and it went up to 12.6V in position 1, and then down to 11.5V at idle (higher than before but still low). I turned on the headlights and other things that were still available, and the voltage starting going down near 10.9-11.1V.

So, at this point (without SDS), is that a dead sign that its the entire alternator, or can a faulty voltage regulator cause this? Also, where exactly does the live "UB" voltage reading originate from thats shown in the cluster? Is it a direct reading from the alternator regulator itself, or is it a combined voltage from all of the components together? Or from something else? Either way, it seems most of the issues are associated with either a faulty voltage regulator, alternator, battery control module, or even the front aux battery relay?

Also, am I missing another check feature to read separate voltages in the car from each of the individual components? Like I said, I thought that would be something only SDS can access. Even if I could see the different voltages in the front and rear batteries that would at least tell me there is a weird fluctuation which would lead me more to believe a faulty Aux Relay or BCM....

Thanks for any and all input guys.

 

The issue has to do with the Alternator. The voltage reading should read somewhere in the 14 volts region when the engine is running.

When I had this issue, i replaced the alternator brushes, instead of the entire alternator and have had no issues with the charging of the batteries after replacement.

 

I should have clarified that my "client" buddy doesnt have an automotive shop but a powersports shop. Believe me, I needed to charge both batteries anyway since I hadn't charged the Aux yesterday after buying it. He doesnt have an alternator testing system simply because dirt bikes and atv's dont have alternators lol.

I see you are in Central Florida....Im about to get a SDS system here locally from a friend but nice to know there are others somewhat close.

Where did you take the alternator to get the brushes replaced?