I did the Big Three over a week ago and starting two days ago my voltage will go from the high 13's to under the halfway point even down to 10ish. This only happens a lot when my a/c is on and my amplifier is going. I have an M500 on a single Type R and I am wondering if it's either my battery or alternator possibly getting weak? I had it tested and they said alternator was good but battery test said it was bad but it charges and starts fine...

 

I'd have the battery re-tested and if it still checks out bad, replace it. I have had so many issues over a crappy battery in the past...

 

I will have the battery re-tested tomorrow and post the results.

 

I'd prob go with the battery if it tested bad & the alternator tested good

 

id definitly recheck the battery and get a different one. i have 2 MRP 500s with 2 12in type Rs and a F300 with out doing the big 3(going to do this week) but mine goes from 14V down to about 13.5V

 

Aiight sounds good guys - thank you for all the input!

 

my guess would be battery too