heat loss from vents

[sk8mystery4lfe]

I have a 2g na 98 eclipse and have a heat problem. if I let the car warm up then sometimes I will have warm air come through the vents but when I start driving the temp guage starts to slowly lower and eventually bury under the cold. I changed the thermostat, and the temperature switch. I will be changing the temperature coolant sensor and I was wondering to get any input. thanks
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[luv2rallye]

During winter months cover 1/2-3/4 of the radiator with cardboard (between radiator and AC condensor) - standard proceedure here in Mn.

 

[Gsxster]

I live in the Midwest and I don't need to cover/block part of my radiator. Did you burp your coolant system? What temp thermostat are you using? I've actually had back to back thermostats fail on me.

 

[98PaprikaAWD]

I've heard some people have issues because the thermostat is installed upside down.

http://www.dsmtuners.com/forums/newbie-forum/188147-thermostat-installed-upside-down-whats-do.html

 

[spyderdrifter]

Failing everything mentioned, you can also pull you dash out and inspect your ventalation passages for the sealing spots and proper function of the air gates.