Barely any heat coming from heater

I have a '95 Tercel. For a couple months now, any time I turn the heater on, it might get luke warm at the warmest. It definitely couldn't be called heat. The temp gauge barely moves past the cold mark. I'm assuming that the problem is my thermostat. Before I change it, is there anything else that could be causing this?

Check for flow through the heater core hoses...if the core is blocked the hoses will be cold relative to the upper return hose where the coolant temp sensor is at.

Your car might also have a heater core flow valve to regulate the temperature. If it is broken or getting plugged up you'll lose flow. Usually located near the firewall penetration where the heater core hoses go in & out.

I like to use an infrared thermometer for hands-off temp checking of hoses when space is tight. AutoZone and Sears sell them for $20 and they're great for auto and home uses.

Hope this helps!

Turns out it was the thermostat. I took it in to have the timing belt and drive belts changed. The manager said it would be best to change the water pump while I was at it. I knew my radiator had seen it's better days, and the mechanic said it was horrible, so I had them change it and the thermostat, too. Turns out the tension pullies for my timing belt were shot too. They saved the parts for me so I could see how bad they were. The bottom of the radiator was totally corroded, etc. The fins just crumbled when I touched them. The mechanic said this car must've been up north originally because road salt is what causes that. He said every part they changed out were the original 1995 parts, including the timing belt. Not bad for a '95 with over 151K miles on it! I had the clutch replaced last month. Not sure if it's just my imagination or not, but the car seems to run so much better now. Hopefully she lasts a long time now with all these new parts. I can't afford a whole lot more! I've had the car for 6 years now, and this is pretty much the first big money I've have to put into it (other than the new rack and pinion last summer). Long live Toyota!