1999 Volvo V70 Engine Stalling

charging system only putting out 12 volts replaced alternator 2 times, have checked all fuses and relays all is well alternator wire to diode in back of alternator looks like it had been fixed before, tested shows 12 volt reference, one thing i did not check is the grounds from battery, it has to be something simple battery has no drain while sitting battery and car stalls when driving please advise

Where are you checking the charging system from? Are you checking from the battery? If you are try squeezing and twisting the positive battery cable and see if voltage changes. If it does then your positive battery cable is the culprit and you will need to replace. Also I believe there is another cable on that same cable from the battery post. If it does that cable goes into the relay box in the engine compartment. Remove the cover and look at the terminal in there and check for cossosion and mybe some burning up in there as well. If it looks bad replace it.

I checked voltage @ battery moved 2 inches down positive cable okay, checked @ relay box okay followed all the way to alt, voltage the same no drain against the battery overnight that means there is no short, something is not regulating the amount of voltage needed to recharge the battery, replaced alternator again and tested, alt again shows good on bench test alternator new, battery new, grounds good all circuit show good. could my supplier be giving me the wroung voltaged alternator for this system is there 2 alts for a 1999 v70. help