Hello Alberto,
You will not be able to get the actual temperature from the A4, but you can get a status to see if it is in a normal range. The OID to query would be:
chEnvAmbientStatus=1.3.6.1.4.1.52.4.1.1.8.1.2
Which has values of:
chEnvAmbientStatus OBJECT-TYPE SYNTAX Integer {
unknown(1), cold(2), cool(3), normal(4), warm(5), hot(6), inoperative(7) }