So lately my cars been a bugger to start... starts fine on the daily but if she sits for a day or two it acts like I have a dead/weak battery. Now driving the voltage meter bounces from time to time, reading 12 to 14.6 volts. Other times it steady at 14.6, but this doesn't cause the starting issue as no matter what it starts after bouncing or steady on the daily (during the work week). When it sits and I turn the ignition on (not to start just on) and it reads 12v but when I crank it drops to 8v but cranks slow. It does the 8v drop normally but cranks once slow then usually fires up, not continuously slow like when it sits. What's the deal... this battery is less than a year old and my alternator is doing what it should... for the most part.

 

You cleaned any Cables or connecting points on that car since you installed the new battery?
Check and clean any connections that relate to the battery,starter and alternator.
DISCONNECT battery when you do this!!!!!
You should also check alternator belt tension to make sure that the alternator can get "the spin" it needs to charge.If the belt is slipping then you could get that Fluctuating voltage.

 

Terminals were cleaned bout 2 months back after the positive terminal came loose and and dual sheath alt pully... tight. I can jump off another battery no problem so I'm thinking amperage issue, need to load test it maybe? But yeah I've gone over all the direct connections to alt and batt. Can a bad alt be causing this...

 

When the voltmeter starts to act funny, measure the output voltage of the alternator via the Black cable bolted to it and see if it acts in the same manner. Also, check the connections to the starter (positive,negative and starter solenoid).

 

Well my alt is shot I believe(reads 12.2v and once it drops to 900rpm it bounces 10 to 11.5) ... I have one laying around from schucks but chances are Ill burn that one up to. Time to look for an fd alt haha.