The car is an 89GT. I am having a charging system problem I just can't figure out. The car charges just fine until you put a load on the charging system. As soon as the headlights are turned on or the blower its begins to discharge. The voltage just gradually drops. The only way to keep it charging is to raise the idle. I have put the factory pulleys back on, I have tried two different alternators, just tried another voltage regulator, tried two batteries. I have no blown fuses, I have good grounds and the battery light proves out. The battery cables are brand new ford cables. I don't really want to put a 3G on right now. The ammeter works correctly.