i tested 2 hours with the heater stuck on the IR sensor just separated by a plastic piece, readings were not good.
I've just moved the heater sticking it just side by side the component, it gives now a slight heating in the sensor area without perturbating it, since then the readings are more reliable.
I'll need a few days to confirm that it's better espcially when the conditions are extreme keeping an eye on values of course.
Using a relay would be so nice of course but my 8 wires are used :
2 wires used for sla and slc i2c interface (humidity, pressure, temperature, sqm, ir)
2 wires for 5v+ and 5- (humidity, pressure, temperature, sqm, ir, rain)
2 wires used for 12 v+ and 12 v- (wind)
2 wires for analogic pins (wind and rain)
I'll need to pull a new cable. If you want to test relay and prepare some code i'll be pleased to test.
A sreenshot of what occurred since i implemented the heater, when i stuck it on the component the values changes about 10 degrees lower, i had to intervene a second time to adjust its position.