i just changed out my thermostat because I had no heat. Thought I would start there but it did nothing. Temp gauge is working fine. No leaks on my passenger side floor. I have a chk eng lite that went on but since my truck is a 95 the auto parts store can't diagnose anything older than a 96. Anyway, I was told a few things; heater core, actuator door mechanism, and a relay under the passenger side dash. Is there a way to trouble shoot my problem before taking apart my dashboard and start replacing each of these? Oh, I should also mention this past summer I flushed the radiator system for the first time in a real long time. Just thought I'd mention it. Thanks for whatever help comes my way.