I just installed a new radiator with 2 14" fans. I used a relay to power up the fans. When the fans turn on, the motor rpm at idle drops like 150+ rpms. It appears to be a stock OEM alternator, brackets, and pulley. I'm guessing it was the stock 55 amp alternator. It's a slightly pumped up 350 and it idles a little lumpy but gets real rough when the fans turn on. It's got a pretty fresh Optima battery. Can the fans pull so much that the alternator struggles so much that it drags down the motor? Would a bigger alternator solve this?
thanks for any suggestions....