Number of fans required to cool a 1992 Mazda Miata engine?

My '92 Miata which I have had for 10 years has been running hot.  Lost my regular
mechanic and new mechanic told me that though there are two fans in the front of the
engine, one is for cooling the engine and the other works only when air conditioning is
being used.  Since I never use air conditioning and it doesn't blow cool anymore anyway
I chalked up that as a reasonable response.  SO, is it true only one engine fan is
required to cool the engine and if I don't use the air conditioning, that fan does not affect
the cooling of the engine itself? Have checked my radiator fluid and all is ok there.  
Hoses are old, so am in the process of replacing those.  Have considered the
thermostat as a potential culprit.  Dash gauge never shows the engine as hot.  Any
ideas?