When the engine is running below approx. 2000 rpm, the heater does not blow heated air. When driving above 2500-3000 rpm, heated air comes and everything seems to be working normal. Temperature controls seem to be operating normally as well. At idle, usually no heat again until the RPMs are increased above 2000-2500. I believe (not positive) I hear the blower fan and air change sound a bit when heat does come on. Operating temps of the engine seem normal. I assume a bad thermostat would be causing the water temperature gauge to be abnormal, so I have not replace it. It seems to be functioning properly as well. Any suggestions? Thank you.

 

Put the controls on manual and verify blower is working. It could be that heat is only produced w/ forward motion (vent air).

Has the cabin air filter been replaced. A very dirty filter can limit air flow.

good luck

 

I'd also verify the engine coolant level, when the engine is cold check the level in the rad and the overflow.

 

Problem seems to be solved and it was a matter of low coolant. Evidently, the coolant level was "on the edge" of acceptability inasmuch that the heater worked fine at times, but often blew cold air at idle speeds. Lesson learned. Thanks again for the help.

 

Thanks for the update. Keep an eye on the coolant level, because you might have a leak. You can get a radiator pressure tester as a loaner tool from most parts stores. You want to make sure the cooling system can hold about 16 psi. The radiator cap should also be able to hold pressure until ~16 psi.

FYI, if the coolant temp gauge in the car starts rising towards H, turn on the heat full blast to help cool the engine.

 

Thanks once again. I appreciate the information. I will test the radiator in the next few days after the weather breaks a bit. I won't be surprised if a leak is present. With 379,000 miles on the ole boy, it is likely time for a few problems to show up. It has been an excellent ride all these years and still looks, rides, and handles very well. I don't want to jinx the car now, but Honda engineering should be commended.