I am the original owner of a 1988 RX7 that has a no heat problem. The temperature gage moves only slightly above cold after warm up and does not go any higher. There is no heat coming from the heater, it just blowes cold air. I have replaced the thermostat three times and still experience the same no heat problem. The hose from the engine to the heater is hot to the touch, but still no heat.

 

The hose on the return side of the heater should be warm, but less warm. If it staying cold, that would signal a restriction in the system. It could possibly a restriction in the heater core.

 

I agree, water from engine should be slightly cooler going back to engine (if tempature is the same, chances are your heater core is plugged). Another thing to look at is a possible stuck heater valve.

 

make sure you have enough waterin the system other wise i agree with the other guys