How do you fix the bad smell coming out of home's air conditioning unit?

Air conditioners have filters so take the filters off and soak them in the tub with a degreaser dish soap. Clean up the rest of what you can on the air conditioner itself (if it's window installed) and spray it with Fabreeze and also give the filters a squirt of it as well. Remember, your air conditioner works hard, picks up odors and dirt, grease and impurities of all sorts so keep those filters clean!