HELP WITH A 2007 DODGE RAM 1500 CONDENSER RAD FAN NEEDED

Hi Folks

I have an 07 ram with a 5.7 engine. Whenever I turn the selector to "defrost/defog" the condenser fan runs continuously (even without the ac on). I understand that the system is designed to have the AC compressor cycle off and on when the selector is in this position regardless if the ac is on or off.

I suspect there is a sensor somewhere for temp or pressure (?) that may be crapped out, but I am unsure where to locate this.

Any help would be appreciated.

Thanks FABO