91 Accord, 4 dr, 4 cyl, automatic, air.
temp of fan forced air is cool to cold unless RPMs are high then it's only warm. I flushed the heater core both ways with garden hose at full pressureand though it wasn't high flow both the in and out lines to the heater core are hot to touch when engine is warm. The heat control valve works and is open (checked when flushing). Air flow is good and the fan regulator works from low to high.
Why doesn't it blow hot air?

thanks,

 

well.....consider replacing the thermostat. you say it only starts to get warm if you hold the rpm high that leads me to believe it may be stuck open. i don't know how hot the hoses are or the temp of the vehicle from where i am.

 

i would suggest the thermostat as well.

 

Thank you. How can I check to see if the flow of air past the heater core isn't blocked or if there is a air flow directional flap/valve not operating properly...is there a diagram of the air flow somewhere?

thanks.

 

There is some discussion of this here: https://www.hondaaccordforum.com/Cau...m_45686/tm.htm
but no diagrams.

You're going to have more difficulty than I did tracking this down because you have AC. But others herecan help you deal with getting the AC out of the way so that you can see what's going on with the flappers.

Good luck.

 

if your car is blowing hot when the RPM's are high (warms up the car more) then that would lead me to believe that your flappers etc are fine. Since you've got air and on occasion warmish air I'd do like hondatech suggested and replace the thermostat with a Honda OEM one. Cheap, quick, easy job...

 

The fact that both lines to the core are hot and the coolant valve is open (I think that's what was said), leads me to think that it might be the flappers.

The slightly warmer air on engine rev tells me that the core is probably getting warmer with increased coolant flow, further warming the air that IS getting from the core into the car.

But Ialsohope it is the thermostat. It's far easier to replace than to get at those flappers - especially in a car with AC.

fixitdad, what kind of temperature control do you have - slider or dial? Whatever it is, does it operate with some smooth resistance, or does it operate really loose and/or uneven?

 

it could be something with the air mix door. i said i didn't know how hot the hoses were. if they were smoking hot then yeah, thermostat is fine. if they are luke warmor so i'd lean toward the thermostat to start with.