we only use B12 in our shop to clean IACs, just getting some of the crap out of there usually does the trick, usually if it cranks fine, and voltage running is good, but a dip when turning on the AC and recovers when the AC is turned off you might need to replace the IAC....rare, but it happens. it is a pretty old car. unplug your IAC and repeat the on/off of the AC and tell us if there is any difference to when the IAC is plugged in. if there isn't than I'm betting an IAC problem assuming the battery is good.
98 GTS RSI TT -proline 510 6766s Infinity GG.
1007RWHP / 1049 RWTQ @ 15 psi. - SOLD