pg_dump still requires password

I want to do auto backup for pg with cronjob. The problem is it equesting for password.

I have tried with pgpass but still it does not work. I created the pgpass as per below:

echo your_host:5432:your_user:your_db:your_pass > ~/.pgpass bash$ chmod 600 ~/.pgpass

My cronjob entry is as below:

/usr/local/pgsql/bin/pg_dump --no-owner  -d helpdesk -U ganesh > /www/htdocs/sg/backup/helpdesk.dump

When I issue the command it is asking for passwd which I cannot used for cronjob to run at midnight.  

Please help. How I do solve this problem.

I have posted this earlier the suggestion was to use pgpass but that does not help. What other way can I achive this.

Regards,

Ganesan