This is for a 2001 Civic LX (Manual Transmission). For a few months now, the heater has only worked while driving, i.e. it works when I'm going 30+ mph, but stops producing heat if I'm stopped at a light for too long. It's been an annoyance, but not much more.

Last night while stopped at a drive-through, I noticed the temperature gauge climbing slowly to the top. The car cooled quickly enough after I turned off the engine, as well as when I got back up to speed on the road. It did the same this morning (didn't have a good opportunity in between to check the symptoms).

I figure that, assuming that the two problems are connected, the fault probably lies with the fan or the radiator, but I thought I'd check whether anyone here has had these particular symptoms together.

Additional: the cabin fan works just fine. I haven't had any problems with the A/C, but haven't used it except as part of the defroster in the last couple weeks.

Edit: May have found same problem w/ solution (https://www.hondacivicforum.com/foru...heating-81136/). I will update here if/when the problem is resolved.

 

I'd do 2 things if I were in your situation. First, change your thermostat. Not a tough job at all if you've ever done any wrenching on your car. If not, check You tube to see how it's done. Second, make sure your antifreeze level is up to where it should be. Too low of a coolant level will result in poor heat from your heater. It will only throw heat when you are driving. Good luck.
Duane