05 Tocoma 4L 6 cyl. 4 WD; heater works well when truck is moving, but get cool air when idling. Temp gauge needle is stable (should eliminate thermostat suspicion), coolant reservoir remains at constant level (should eliminate suspicion of coolant leak or air pocket), not hearing any strange noises from heater or water pump. Even though there are no coolant leaks, could the water pump still be a possible cause of problem? Any other thoughts besides water pump ? Thanks.

just a idea

when you have the heat set to defrost or any of the defog settings ( both defrost and foot heat) that does turn on the a/c

they use the a/c to remove the moisture

can't remember if it is for fresh air or recirculate, one of the two only

when you have the heat set to defrost or any of the defog settings ( both defrost and foot heat) that does turn on the a/c

they use the a/c to remove the moisture
It's true that the compressor engages to dehumidify the air, but the temperature is set by the dial.... if you select 'hot', you should get hot air regardless of whether the A/C is on or not. Put another way, engaging the compressor does not mean you automatically get cold air.

To the OP, sorry, I don't know what might be causing your problem. I'm guessing thermostat b/c that's what should keep the coolant hot enough for your heater/defroster to work properly. If that's the case, I have no idea why the temp gauge reads normal, unless it has something to do with the location of the sending unit.

I believe the temperature is always full hot, and cooler settings involve a blend door (mixing in cold air). Maybe there's a problem with the operation of your blend door...

streamwalker:

Do you have towing package (engine oil cooler)?