how to disable iDRAC ssl

When i use Dell  R730 with firmware version 2.43.43.43, i always got the error log "Certificate is invalid - self signed certificate". I can find some configure items of the SSL and each iDRAC has one self-signed certificate. but i can't find the place to disable the SSL, i mean disable HTTPS but use HTTP instead.  I find someone in community said about this, but can't find the right setting for it. Does anybody know about how to do this ?