I just went thru this. Red light indicating bad connection. It was a bad fuse.
When I first checked, I moved the fuse holder that looked bad and it fell apart. Aha, I thought. That was the problem. I replaced the fuse holder and fuse and reconnected only to have the same problem indicating. After changing things around determined that another connection was bad. I took the removed new fuse and put it in one of the other two on the other bank and red light went away. The original fuse was ok (it was the connection that broke) so I put the original fuse I had removed to the other one and viola, it works.
I hope this makes sense. Short story, check fuse first before buying a new charger. My charger is old and is still performing as it should with the new fuse and repaired connection.
LOVE GOLD Jimmy