Do you know why the average asec weight is much higher in 2013?
Correct me if I’m wrong, but I think you meant the average weight is higher in 2014? You can see on the ASECWT Comparability tab that the weights are calculated to sum to the full population for each of two subsamples in 2014. You can read more about this here. Because of this, the weights are higher than in other years.
Yes, in the 2014 ASEC (CY 2013) there is a 3/8th and a 5/8th sample, and they received different survey questions. Census has a ton of guidance on this, but in practical terms, I typically keep all respondents and adjust their weights by 3/8ths or 5/8th based on the HFLAG variable.