Ok Guys here's what I got... You guys are a bunch of car nuts so I figure I'd throw this out there and see if I get any bite. My Dad has a 92 Nissan Max runs like a dream and everything works... Here my question now that it's getting cold in TN we flipped the heater on in the car and nothing but cold air . But if you floor the car the air will warm up until you let off the gas.... I am puzzled the a/c cold works like a dream.... any ideas would be awesome thanks

 

Low coolant level

 

water pump not circulating or on/off valve not opening properly

 

not a rotary engine... wont make heat.

 

the heater core might be clogged. check to see if it has a valve on the hoses to the heater core if that works fine then take both hoses lose in the engine bay and hook a garden hose up to one and see how well it flows.

 

Either low coolant level, or there is a valve that is controlled by the heat selector which can sometimes go bad. Either way, it should be an easy fix.

 

I'd start with a thourough coolant flush and fill up (make sure you FLUSH the system, don't just change the fluid)

See if that works.
If not, then it's valve problems most likely...