is there an easy way to find out how my regulator is doing? the voltage at startup is around 14.2v and drops slowly over 3-4mins to 13.2v. sometimes it goes as far down as 12.8v

and ive had the interior light blow recently too.

That sounds pretty normal to me. I think the standard constant voltage is around 13.8 so it seems that your battery is slightly low at the start, the load increases to increase the voltage to improve the charging and then it is back to normal. sounds normal to me but then again i am no autoelectrician.

at times its been dropping to 12.5v when im on the brake peddle.

i think its related to heat. but im thinking it may be on the way out

How are you reading the voltage? From the in dash diagnostics (EF/L) or in dash voltmeter (high series) or are you using an actual multimeter?

The reason I ask is because the in dash systems seem to read up to 1V low. Running the in dash diagnostics (you know press odo reset 3 times, hold till seat belt light goes out then release) I get a reading of 12.8-13.1 but using a multi I get 13.8.

cheers
Scott

My HU has a feature and the dash is near the same. i cant see both at the same time though.