a winter warm up tip

[SCoupe]

Confused here. On my Civic VX, doesn't the thermostat just halt most (all) coolent flow through the radiator (and heater core as an extension) until some minimum temperature is met? In that case, what difference would it make what temp you set the heater on because no radiator fluid is getting there yet anyway ?

[Jay2TheRescue]

Most cars have a heater bypass hose that bypasses the thermostat. Its usually that tiny 4" long "S" shaped hose, that (at least on my cars) is a real PITA to change.

[trollbait]

I keep the air intake on recirculate

On some cars, recirculate turns on the compressor.

[aalb1]

Originally Posted by SCoupe

Confused here. On my Civic VX, doesn't the thermostat just halt most (all) coolent flow through the radiator (and heater core as an extension) until some minimum temperature is met? In that case, what difference would it make what temp you set the heater on because no radiator fluid is getting there yet anyway ?

For all who are still in question on how this works here is a great visual from my Civic Service Manual. Remember that the heater core works like a mini-radiator. In this picture it shows the heater valve set to "Hot" but for the sake of discussion imagine it "closed" and set to "cold." If it is "closed" or set to "cold" then it does not let the coolant circulate freely through the heater core. Rather the coolant just sits there. Any heat loss is ambient heat loss due to being close to the heater core (as illustrated by the blending of the red and the blue) rather than being direct heat loss from flowing through the heater core.

[JanGeo]

Originally Posted by trollbait

On some cars, recirculate turns on the compressor.

Usually the defrost setting will run the compressor even if on recirculate although the owners manual says to have it on fresh air in my xB. BUT if you have it on defrost and do not run the fan then the compressor will NOT run and you have to rely on the forced air flow to move air through the system from the car moving or the wind. Also not turning the vent control all the way to defrost prevents the compressor from turning on and still lets some air flow onto the windshield to clear it.

The other thing I do is to keep the vent on recirculate when parked to keep the heat in the car when it gets warmed up by the sun and to reduce the dust intake.

Great find there Jay! I will have to look for one of those 12 volt electric heaters.

[theholycow]

I'm pretty sure both my vehicles run the compressor when recirc is on, regardless of any other settings. Even if the fan is off you can feel that the air has passed the compressor.

[zero_gravity]

nice pic and explanation aalb1. should clear up any questions out there

[JanGeo]

Usually the compressor will not run without the fan because it would cause the evaporator to ice up rather quickly if the cold is not removed fast enough. Not sure why they (Toyota) wants the recirculate off when defrosting because it would tend to dry the air out rather well I would think.

[aalb1]

Originally Posted by JanGeo

Not sure why they (Toyota) wants the recirculate off when defrosting because it would tend to dry the air out rather well I would think.

All cars that have this "Passive Fresh Air Function" when setting the vents on defrost do this because it defrosts windows quicker. My car doesn't have this and I have trouble with defrosting my windows with recirculate on. When I switch it to fresh air it clears up right away.

[JanGeo]

That would depend upon how humid the air inside the vehicle is - like if you got soaking wet and climbed into your car and the floor had a puddle on it then yeah things would get a little foggy. But with the A/C cooling the air to remove moisture then getting it heated by the heater it would dry out pretty quick compared to the outside air that could be pea soup fog like we get sometimes here in Newport. It's better (more efficient) to keep the air dry from inside the car than to try to constantly dry the wet air coming in from outside.