Pelaez and Yon de Luisa, named operations president, will work together under a council of directors headed by Emilio Azcarraga, the Azteca based club's owner and president of the powerful media organisation Televisa.
"I have brought a magic wand to resolve the situation, I want to build a competitive working group. Work and humility are the words that will set our path," the 48-year-old told reporters after his presentation.
America, one of Mexico's two biggest and most successful clubs with arch-rivals Guadalajara, are at one of their lowest ebbs after finishing one from bottom of the league standings and failing to reach the Apertura championship quarter-finals.
The Eagles put their whole squad, which includes a number of South American internationals, on the transfer list after their closing 3-1 defeat at Cruz Azul last weekend and said they would promote players from the youth scheme.
De Luisa announced the dismissal of Tena and Pelaez's initial tasks will be to find a new coach, give the squad a solid Mexican base plus a few foreign signings and win as many titles as possible in the run-in to America's centenary in 2016.
"Things couldn't be worse, there is great concern over the spiritual aspect [of the team]. We'll try to build a good team in quality and quantity," said Pelaez, who played for America, Necaxa, Guadalajara and Mexico at the 1998 World Cup in France.
Pelaez said he would speak with players in the current squad to find out who was keen to stay at America, whose last big idol, Paraguayan striker Salvador Cabanas, was shot in the head during a row in a Mexico City bar and has not played since.
"To be at America is a privilege, some will go others will come in. I think there's a very good squad, we have good players [but] I also think that in some areas of the pitch we lack a player who can tip the balance [favourably]," he said.
America enjoyed a golden era in the 1980s when they won five of their 10 league titles but they have only lifted two since, in 2002 and 2005.
Guadalajara, who finished top of the round-robin phase of the championship, are favourites to win a record 12th Mexican league title.
