Mx-5 Overheating Issue

I Just Purchased A 1990 Mx-5 And There Seems To Be A Problem I Can't Find! It Runs Hot While Idling(after A While) And Does The Same Thing Running Hard Down The Road. If I Turn The Heat On It Brings It Down.the Motor Only Has About 2,000 Grand On It ,the Water Pump Seems To Be Fine And The T-stat Is New.the Driver Side Fan Comes On But The Other Does Not. I Think It Comes On Only When The Ac Is On. Is There Something I Am Missing,any Input Would Be Great!

Thanks B

replace all hoses, t-stat, flush the radiator, hardwire both fans together, and read the forums at www.miata.net