300m need help

I have been working on a 2000 300m. The problem is the cooling fans are not working when the a/c is on causing the pressure to build and blow out of the relief valve. the fans work fine when the engine is up to temp but something is not telling them to kick when the a/c is on. have replaced a/c pressure sensor, expansion valve, and tested and/or replaced all fuses and relays. btw the a/c is charged at the moment. Any help would be great.

Thanks

High Speed Relay?

I know you said you checked the relays, but just wondering...

Other than that, no clue.

replaced it with a new one thanks