My Honda is a 97 Accord EX with approximately 154K miles. I parked it for a year and now am in the process of "rejuvenating" it which has turned me into somewhat of a weekend mechanic. Over the past few weeks, I have wrestled with valve gaskets and grommets till the wee hours of the morning, replaced my catalytic converter, manually cleaned my EGR valve and intake manifoild of carbon deposits, replaced the thermostat along with radiator hoses, and NOW my heater appears it will be the next project coming up /sigh

This may be a multipart issue. Here is what happens when I turn my heater on: For one, the blower motor only works when you turn it on high and then it's a bit loud but blowing like a champ. I hear this is an issue of the motor (noisy) and resistor switch (can't set to lower setting) needing replacing. I have done neither yet because even when the car has warmed up, I don't feel any warm air. On a warmer day I can feel a little warm air. On a cold day (like today) forget it.

From the information I have gathered, my resistor switch is what regulates the lower settings of my heater/AC, otherwise it will only function on High. My blower motor may be noisy but it's still blowing plenty hard. Someone told me to check my heater valve, maybe it is stuck. ...Not quite sure where this is just yet but I will check that before the next step which has me hesitant:

...I saw a video on Youtube, some guy named Eric the Car Guy, demonstrate flushing out a heater core. That looked so messy but it appeared to be basically a backwash. If my heater valve turns out to be fine, should this be my next step in order to get it operational? If I can just get some warm air blowing out somehow, I'll gladly replace the resistor switch and blower motor. I just don't feel it is necessary just yet until I actually diagnose and solve the main issue. In your opinions, have I missed something before I begin this project?

 

If you haven't bled the coolant system adequately you could have heater problems. Have someone move the temperature lever and you should see cable on heater control valve move. It's near the firewall and has a heater hose attatched to it. If it moves it's likely good.

 

^^ All good advice. If the cable moves then the next step is flushing but, you're gonna have to crack the system so, check the valve by eye just to be sure.

I've done that flush and I had to do it 3 times to get all the gunk out- and it only worked for a season. You're experience may differ.

Make sure to bleed the hell out of the system when you're done. You're probably gonna have to massage some hoses.

If the blower motor is only working on high it's almost always the resistor.

 

What is the reading on your temp gauge? Make sure the engine is getting up to operating temperature. Also, once the car is at operating temperature, carefully feel the hoses starting from the radiator to make sure they are hot, then back to the input and output hose of the heater core on the firewall. This should give you an idea if there is a clog somewhere. Once you have established that, the flush should help. And as the others have said, make sure to bleed the system properly. You may want to replace your thermostat at the same time as the flush since it is cheap and prevents you from having to drain it again later.