I hear this being written by many people in this thread and it's absolutely false. Although you are cooling the coolant by having the heater fan going before the engine is warm, that heat is going somewhere, and it is going into the cab of the vehicle.
Will it be a noticable amount? no, probably not, but if you're going to get technical, it is heating the cab up, however little.
This is of course assuming that it's the same temperature inside the car as outside. If the cab of the vehicle is already warmer than the environment (b/c of the greenhouse effect of the windows, or it was in a garage or something), then you'd be better off leaving the heater off.
I think it's a pschological thing. People think it's like turning on the hot water in your house, letting the cold water in your pipes run through to get to the hot water.
dullard
Elite Member
- May 21, 2001
- 26,029
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1) With air running through the engine, the air will pick up some heat (not much, but some). There is no possible way it couldn't pick up some heat since the engine will be very slightly hotter than the surrounding air.
2) Thus with heat leaving the engine, into the air, the engine will heat slower. However, this effect will be very small.
3) With that very slightly heated air entering the vehicle interior, that heat will remain in the interior. Thus the car will (unnoticibly) heat up faster with it on.
4) However, temperature is only one part of the heat transfer equation. You also need to consider the velocity of the air. Cold, still air around your body doesn't cool you much. But high velocity cold air hitting you will cool you quickly.
5) Conclusion: keep it off until the engine heats if you want to be warm.
2) Thus with heat leaving the engine, into the air, the engine will heat slower. However, this effect will be very small.
3) With that very slightly heated air entering the vehicle interior, that heat will remain in the interior. Thus the car will (unnoticibly) heat up faster with it on.
4) However, temperature is only one part of the heat transfer equation. You also need to consider the velocity of the air. Cold, still air around your body doesn't cool you much. But high velocity cold air hitting you will cool you quickly.
5) Conclusion: keep it off until the engine heats if you want to be warm.
DrPizza
Administrator Elite Member Goat Whisperer
I agree with Vic: no difference, or at least, no noticeable difference.
To whomever "timed it" to prove it? Yeah, right. How did you perform that experiment? You needed identical starting conditions, which I doubt you had.
Factors some of you are forgetting: the engine block isn't always in thermal equilibrium with the surroundings.. in my area, the temperature drops during the night, often quite considerably. Just a guess, but the engine block is probably at least 4 or 5 degrees warmer than it is outdoors when I turn the car on at 6am. At different times during the day, it probably varies whether the engine block is colder or warmer than than the ambient air.
Also, I question: the thermostat doesn't open until the coolant reaches a certain temperature... Does coolant flow through the heater core while the thermostat is closed?
To whomever "timed it" to prove it? Yeah, right. How did you perform that experiment? You needed identical starting conditions, which I doubt you had.
Factors some of you are forgetting: the engine block isn't always in thermal equilibrium with the surroundings.. in my area, the temperature drops during the night, often quite considerably. Just a guess, but the engine block is probably at least 4 or 5 degrees warmer than it is outdoors when I turn the car on at 6am. At different times during the day, it probably varies whether the engine block is colder or warmer than than the ambient air.
Also, I question: the thermostat doesn't open until the coolant reaches a certain temperature... Does coolant flow through the heater core while the thermostat is closed?
My solution to get the engine warmed up faster? Turn on the AC as you're driving. It causes the engine to work more than it would normally. Cuts a few minutes off of regular warming time.
Which is why if your thermostat is stuck closed and you absolutely have to drive, turn your defrost on max, and make it a quick trip.
I turn the heater on right away, but thats because I don't stay inside the car while it's warming up and when I come back I want it to be warm.
Some vehicles, when you turn the defroster on instead of the heater, while the car is still cold, will automatically turn the AC compressor on. They can get heat off an AC system faster than they can an engine. Then when the engine starts putting out heat, the AC turns off.
Originally posted by: bmacd
I start the car, turn the heat on, and leave it for five minutes. When i come back, it's gone.
-=bmacd=-
Fixed.
radioouman
Diamond Member
- Nov 4, 2002
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What is your definition of cold and warm?
I turn my defrost on immediately when it is cold, and I turn the blower up to half or 3/4. The reason? I don't want condensation on my windshield and windows! Even if it is blowing cold air, it will prevent your windows fogging up. And that brings me to my next point. Even if the air doesn't feel warm to you, the air coming through your vents will very quickly rise above freezing, so if I have ice on my windshield, blowing 50 degree air on the windshield to warm it up is more helpful at thawing the ice than no air flow at all. (even though it doesn't feel warm to me.)
I turn my defrost on immediately when it is cold, and I turn the blower up to half or 3/4. The reason? I don't want condensation on my windshield and windows! Even if it is blowing cold air, it will prevent your windows fogging up. And that brings me to my next point. Even if the air doesn't feel warm to you, the air coming through your vents will very quickly rise above freezing, so if I have ice on my windshield, blowing 50 degree air on the windshield to warm it up is more helpful at thawing the ice than no air flow at all. (even though it doesn't feel warm to me.)
I start my car, start the heater, go back in the house, forget to open the garage door, and DIE of Carbon Monoxide |-: Not funny I knew someone that did it on purpose )-:
if you dont turn it on, you wont know when it starts to get warm.
as for the a/c point someone raised, the reason that comes on with defrost settings is it lowers humidity, which is made of the same stuff that fogs the windows, water.
as for the a/c point someone raised, the reason that comes on with defrost settings is it lowers humidity, which is made of the same stuff that fogs the windows, water.
I've done it both ways: Turn car on, don't turn on heat. AND Turn car on, turn heat on full blast.
Turning on the heat full blast as soon as I start up my car actually made the engine warm up faster, and thus the inside of my car warmed up quicker.
I think it's because the fan blowing the heat puts an added strain on the engine making it warm up faster, and warming up the interior faster as well.
And, I've had plenty of cold mornings to test it out on. I live in the NC mountains.
Where's Mythbusters...
Turning on the heat full blast as soon as I start up my car actually made the engine warm up faster, and thus the inside of my car warmed up quicker.
I think it's because the fan blowing the heat puts an added strain on the engine making it warm up faster, and warming up the interior faster as well.
And, I've had plenty of cold mornings to test it out on. I live in the NC mountains.
Where's Mythbusters...
i just wait until the temperature gauge (coolant) reads normal and then turn on the blower to get warm air otherwise it would blow out cold air and make me colder.
You look at the little temperature dial and see when it gets somewhere past "C". I usually wait for mine to hit midway point.
I get heat almost immediately on my Civic Hybrid when I first start the car for a cold morning. I can't imagine how much better the heating/cooling system is on the current HCH and Prius models are with electronic systems running from the battery instead of the engine.
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