1994 Other Mitsubishi Models No output from New Alternator

Mirage. Just replaced battery & alternator. Had the fuses checked & seemed fine. Yet the new alternator will not put out a charge. Belt and connections seem tight, cannot find any loose wires. Had the car a month and was running fine, my son cleaned the engine (no water) WD40 only and now it won't charge. Please advise where to next? I'm $250 into it now and still the same problem.
Thank you