Load Balancer Doesnt Work

[gendrix]

this is not my first pf sense load balancer project. but this time, i got trouble with load balancer
today I was balancing 3 wans with 3 ADSL Modems. the modems are in connect status. I use DNS Ip for monitoring ip.

i can ping the DNS ip from the pc if i directly connect the PC to the modem, or i bridge the Lan interface with WAN. But Pings from PF sense to DNS IP via Wan interface always Failed. i can see the blink of Modem's Lan LED Light and Ethernet's LED Light
If i ping the modem from the PFsense it never failed.The Balancer status is online if i use wan's gateway(modem's ip) as monitoring ip, but internet is off.

any idea ? i have reinstalled my pfsense several times all night long.

is it my settings ? or my LAN Card  in trouble ?