Collection select is cleaning after doing search issue

Collection select is cleaning after doing search issue

I did a search using ajax using 2 collections select but after doing
SEARCH the information selected my collection select is cleaned.How can i
fix this problem?
Here is my controller
class PolicyManagement::PolicyController < ApplicationController
def update_products
cia =CiaEnsure.find(params[:cia_ensure_id])
products = PolicyProduct.find(:all,:conditions=>['cia_ensure_id =
?',params[:cia_ensure_id] ] )
render :update do |page|
page.replace_html 'products', :partial => 'products', :object =>
products
end
end
def generate_print_type_product
@cias = CiaEnsure.find(:all)
@products = PolicyProduct.find(:all,:conditions=>['cia_ensure_id =
?',params[:cia_ensure_id].to_i ] )
@search = Policy.find(:all,:conditions =>['cia_ensure_id = ? AND
policy_product_id = ? ',params[:cia_ensure_id].to_i
,params[:product_id].to_i ] )
end
end
Here is my view
<% form_tag
:controller=>"policy_management/policy",:action=>"generate_print_type_product"
do %>
Cia Secure:
<%= collection_select(nil, :cia_ensure_id, @cias, :id, :short_name,
{:prompt => "Select"},
{:onchange => "#{remote_function(
:url => {:action => "update_products"} ,
:with => " 'cia_ensure_id=' +value" ) }"
}) %>
Product
<div id="products">
<%= render :partial => 'products', :object => @products
</div>
<%= submit_tag "Buscar", :name => nil %>
<% end %>
This is my partial view _products.erb
<%= collection_select( nil,:product_id, products, :id, :name,
{:prompt => "Select Product "}) %>
I will really appreciate help