A/C fan issues

When I turn on the A/C the fan turns it self off, and if I turn the a/c off the fan keeps running even with the car off… WHY??? :hmm::hmm::hmm:

Have an other quick question… Does 4-1 headers work on a 91 integra GS?? or do I need to get a traccion bar :bang:

Thanks for the help!!! :hi5: