Vents blowing hot air when off

[jediknight36]

Well, it is finally cool enough to roll down the windows here in Tejas, and to conserve fuel, I have been doing so. This morning, I hoped in the smart and realised it was the coolest morning in months, with a temp of 56*. I made sure my AC was off, the fan was off and the temp was set all the way down. I rolled the windows down, turned the seat warmer on (helps with the lower back) and started rolling.

After about 5 min, I could feel wisps of warm air over my hands. I figured it was the wind whipping the seat warmer air back to the wheel. A few minutes later, I got a call so I rolled the windows up and turned the fan on... and it was WARM! The intakes had been forcing air to the vents. Ok, but my heater was on?!

The only thing I can figure out was that the lowest temp on the dial was still warmer than the air I was letting in, turning on the heater. Anyone have another idea?

[smartSEATTLE]

Originally Posted by jediknight36

Well, it is finally cool enough to roll down the windows here in Tejas, and to conserve fuel, I have been doing so. This morning, I hoped in the smart and realised it was the coolest morning in months, with a temp of 56*. I made sure my AC was off, the fan was off and the temp was set all the way down. I rolled the windows down, turned the seat warmer on (helps with the lower back) and started rolling.

After about 5 min, I could feel wisps of warm air over my hands. I figured it was the wind whipping the seat warmer air back to the wheel. A few minutes later, I got a call so I rolled the windows up and turned the fan on... and it was WARM! The intakes had been forcing air to the vents. Ok, but my heater was on?!

The only thing I can figure out was that the lowest temp on the dial was still warmer than the air I was letting in, turning on the heater. Anyone have another idea?

I have not had a chance to test a theory but might have something to try.

Your fresh air intake vent for the smart is located center of the lower windshield sill. Now if you remove your service flap/hood you will see the air ducts go straight down then take a bend and go back into the air box.

What I think might be happening and here is where I have not played around with air box is that the ducts go right over top of the radiator, and they get pretty close.

So in theory lets say your coolant is at 200 degree and bleeding off heat, as it should, that could be heating the air up in the air box as it blows over it.

Hopefully I am not starting a engineering debate here as I did not design the thing, I just have to try and figure it out how it works.