I believe the replacement was a 50 amp and the stock was 40 amp. Besides which from the heat of the bike and the age also they do get weak too. You can use an automotive breaker available at an auto parts store to replace it with. Just hook it up the same as the stock breaker. Usually they have two different terminal colors, just replace it the way the factory unit was hooked up.
There was a problem with them and there was also a recall I believe if you want to check with your dealer but the part is a cheap one.
Auto Recalls: Vehicles - HARLEY DAVIDSON -- Nolo