Hot air on cold selection - problem or normal?

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dhobbs

Senior member
OK, not sure if this is normal or a problem, so here goes..

With the roof down and when it's hot outside I turn the temp down to min, unfortunately I still get warm air out of the vents (both face and footwell).
Now this is with the A/C off. The A/C works fine and the heat does vary when you select to hot/cold etc.
It's only noticable when it's really hot outside, but it feels like the cabin air is still mixing with the engine heat.
It feels wrong to have the A/C on with the roof down but if that's the solution.

When it's cold outside, there are no perceived problems. Now am I expecting too much or is there an issue?

Oh, I have the semi automatic climate control (turn dial to temp and leave alone) if that helps.


Thanks
 
I'm no expert but with all cars I've had this would be the case. It is my understanding that if you have the A/C off, you will simply get air of the temperature outside passed through to you (i.e. no heat applied to the air).

If you turn the air con on, the air should turn cool as the air conditioning unit works on the air sucked in through the front.

Essentially, if it were 50c outside, I wouldn't think there would be any point having the blower on with the A/C off as it's just going to blow 50c air onto your face.
 
dhobbs said:
It's only noticable when it's really hot outside, but it feels like the cabin air is still mixing with the engine heat.
Click to expand...

This is precisely what is happening. The "cold" air intakes are located just in front of the windscreen (outside, under the window wipers), and you're always going to get residual heat from the engine bay soaking in.

There is no residual "cooling" that takes place. it will never be colder than the ambient air temp, and will always be warmer (if even by a fraction of a degree at times) than that.
exponentially so in slow moving air, where it can be heated by the engine bay/bonnet before making it's way into the air ducts.
 
As this is my first roadster I wasn't sure if this is normal.

I appreciate that it will be ambient at best. I also compared the outside air (stick hand out of window) against the air vents, and there is a noticable difference
From some of my older cars I know there is a small heat exchanger in the car so was wondering how to test the flap that controls the temperature to see if it is fully closed/open (maybe for piece of mind).
Is it a plastic flap or is it embedded into the cooling system as a valve?

Maybe the answer is to switch the A/C on
 
it's a couple of flaps embedded in the back of the heater unit, if memory serves.

if it's any help, I turn AC on on the hot days, point it at the feet and enjoy.

I guess the best way to test is wait till the car is cold, then turn the key to pos 2, turn the fan to cold and on, and monitor the temp with an electronic thermometer.
then, after you've got a base reading, start the car without touching the controls, and keep monitoring the air temp as the car temp rises.
then compare..?
 
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