Hi, How do I convert the raw temp returned from AIRCON ZONE_TEMPERATURE into celsius? Thanks

Temperatures are expressed in units of 1/256 of a degree Celsius. So just convert it to real and divide it by 256. It's all described in the Air Conditioning Application protocol document on the CIS web-site.

If its in 1/256 of a degree, then multiply by 256 (not divide). You can probably also imagine a few other fiddles that could be done using a couple of bytes (eg a byte for the part before the decimal point and a byte for the part after).

Divide is correct. If the units are 1/256 of a degree, then a value of say 512 is 2 degrees, which is 512 divided by 256.