WAL replication question

I am relatively new to PostgreSQL and have a question on WAL replication. I have two servers with one designated as Master. Both Master and Slave are configured simularly, with exception of the recovery.conf file only exists on the Slave.

For failover, I am using the trigger file capability to "promote" the Slave in the event that the Master fails. That seems to work well. The question I have is when the former Master comes back on line, is there a way to make it a slave (adding the recovery.conf file) without restarting the PostgreSQL process? I currently do this with a restart, which works well, but we are using Pacemaker and the PostgreSQL resource goes away and takes the node down until it comes up. We would rather the node not go down if possible.

Is there a way to do this? Thank you in advance.

Keith