Heater Problem Temperature Drops

[dustyk]

I have an odd problem with a 96 240sx that I just picked up. Everything runs fine but when I turn the heater on, the factory coolant temps start to fall. (it's low 60s outside when I did this) Also, the heater doesnt really get hot, just sort of stays warm.

Im thinking that the thermostat is stuck open and my engine is running too cold when I turn the heater on.

Anyone have any input on this?

[speed-s13]

sound like a t-stat to me. how cool does the engine run?