My car is plagued with that ever famous 90 2+2 no heat problem... we took the dash all the way apart we put new hoses inbetween the heater core and engine, we replaced the heater core, we flushed the heating and cooling system, all to no avail the air doesn't heat up at all im beginning to wonder if it has anything to do with the sensor on the top of the dash this is an autmatic climate controll system.....do you have any idea what else could be wrong.. this is something me and my father have been working on for almost a year now to solve and now a years worth of work has gone down the drain..........HELP

 

did you check the thermostat? It seems like an easy one to start with. Check your coolant temp and temp guage sensors as well, they might be corroded or not sending proper signals. You might wanna also double check that your heater inlet and outlet hoses aren't blocked. But I'm guessing you might have already done that. If you think it might be the temp sensor inside the car, just check to make sure that the fan inside it is still spinning providing it the necessary air.
http://www.ttzd.com/tech/autocctech.html
This might help. Link to "climate control diagnostics page".
I hope this helps. good luck

 

we replaced the thermostat with a brand new one from nissan. so i wouldnt think that it would be deffected or anything but i will look into everything else you said. Thanks rizz.