Honda Accord 2004 Heater doesn't work when idle
I have a Honda Accord 2004 Lx 4 cyl with 140k miles on it, recently the heater stopped working and the car overheated.
I took it to a mechanic he said the Thermostat needs to be changed, I changed the thermostat (It was a Honda genuine part), the overheating problem got solved but since then the heater doesn't work when idling.
It works fine when driving or when the engine revved up to 2000 rpm, but as soon as I stop at a signal it blows cold air.
I tried accelerating up to 6000 to 7000 rpm for some time and it seemed working good after that for some time (heater worked fine when idling), and after that the same thing happens,
can someone please tell me where could be the problem is, I do not know much about the cars...
Thanks in advance...