I have a 2004 CLK500 with dual automatic climate control.

When I turn the passenger temp up to "HI" I feel heat come out of the vents, but when I lower the temp to 89 or 88 degrees the air is cold

Is this normal?

Is there something I am doing wrong?

 

that reminds me of a problem i had too. Cold air was coming out when the heat was turned on. I had the settings on 77 degrees and relatively high fan. The air was cold.

I did notice the blue colored controls in between the center vents and turned it so that it would be closed. I dunno if that's what did it, but it blew out hot air after that.

I could be dead wrong. I actually have no idea what that center blue control does. Does it close out the outside air or something?