Civic Heater Mystery

i have a 2005 civic LX

i live in atlanta - not really all that cold

usually, the temp gauge gets to the middle in about 5 minutes

it stays there, nothing unusual

heater inside the car warms up a little by then

but it doesn;t really get warm til about 10 more minutes

then it;s very warm

gauge hasn;t moved - it;s still in the middle

why does it do this?

if the water temp gauge doesn;t get any hotter, how come the inside heater does?

is there some secondary thermostat that doesn;t let the really hot water into the heater core until later?


You are seeing that the motor is up to operating temp, and then the thermostat opens and allows coolant to flow into the radiator and the heater core. So, the uptake of temp in those “radiators” is a bit behind the motor temp.

Most folks just see the guage is moving up and assume the heat is there, but it takes a few more minutes before you’ll get full heat out of your vents in the cabin. Remember, all the tubing, pipes, and ducts are cold and they soak up some of your heat when you first warm up the cabin.

the temp gauge doesn;t move though, after the first 5 minutes
it takes 5 minutes to get to the middle - then it stays there
and there is not a lot of heat
but after 15 minutes, the heat suddenly gets really hot, yet the gauge still hasn;t moved again


I think that some manufacturers scale their temperature gauges so that the needle stays still in the middle for a range of temperatures that are considered normal. In other words, even though the gauge hasn’t moved, the engine has become hotter.

also, i have never had a car that didn;t put out max heat in about 5 minutes
that seems odd too


follow the hoses to the heater core and check temperature there, them check if the blemder door is working.