996 Heater only blows hot on high !

[kneeslider916]

Gents,,
I have just discovered that my much loved 996 C4S will only blow out hot air when I wind it all the way up to high, below that I get ambient/tepid. A bit annoying, everything works on the controls, fan speed etc, I'm struggling to comprehend what could be wrong. Anyone got any ideas what it may be?

[Pope]

Likely to be a temperature sensor - either interior or exterior (behind NS vent bezel - interior / in OS front bumper grille - exterior). The temp is measured and the required output supplied to heat / cool the cabin. If the measured temp is higher than actual (due to a faulty sensor) the system will not function as you expect.

An example: measured interior temp = 44 degrees C - supplied output at anything other than high or low will be cool as you are requesting air at between 16-29 degrees C. The high and low settings do not compare the ambient conditions hence the hot output when set to high.

[thegoose]

Following on from that do a search for definitions for the secret codes for various parameters (Inc various temp sensors) that can be accessed by pressing the top and bottom buttons on the climate control together for a few seconds. You should then see the actual values and determine which sensor is giving the wrong reading.

[kneeslider916]

Gentlemen, thanks for the guidance, I shall investigate further and attempt a fix.