Second Model dissapear on chronoconectivity

Hi,

I have my main model that is called Demandante that works great.

When I add a second model called Relacion and add a where condition:

<?php
return array("Demandante.relacion" => "Relacion.idRelacion");
?>

the model Relacion dissapear when I press "Save" button.

I am tying to make this query:

Select r.relacion
from z2ma5_sioa_demandante d,sioa-demRelacion r
where d.relacion = r.idRelacion;

Can you help me? Thanks,

Joaquín