Or is it that Manual only allows you to change the vents that the air comes out of, but the unit changes the fan spped regardless. Whereas Auto changes the fam speed but selects which vents to use?

I duuno, but that rings a bell!!
 
Arrghhh im having these problems with mine...

on manual the car ups the fan speed a few notches every 30 secs or so til its boiling and never changes again!

It also suddenly looses all heat about 45mins in to a journey!

Anyone help?
 
Mine does this, changing fan speed.

I find that if I set the temp and fan speed and the actual car temp is different to the temp I've set, the unit cranks up the fan speed forcing me to turn it down again. However, once I've turned the speed down again, it doesn't happen again until I change the temperature.

It may be something to do with adjusting the cabin temp to that set by yourself regardless of the fan speed you've set?
Mine does exactly that too. It has done from day one. I guess it's normal.
 
sorry not read all this thread however adjusting the temp is adjusting the auto setting....you should notice "man" will go off on the display

that is why the fans start doing thier own thing.

the manual buttons regardless of temp are to change the rate at which the air is coming out.

Sorry if this repeating what has been said i haven't read the whole thread like i said