ok heres the deal, 2 of the valves are working perfect but the other 2 which are the front, seem to not be, they click as if they work but wont let air in to the bag, could this be beacuse they are frozen? or something else? 
let me know 
thanks 
JJ
 
take the valve apart and see if theres anything in there.  i never had a problem w/ my valves freezing but i had a problem w/ one of them getting stuck open