Temp 2 is the temperature of the intake air.
There is an NTC (negative temperature coefficient) sensor just inside the air intake filter.
For some reason, Panasonic are using the NTS's inverted, i.e. the number increases when the temp drops. They probably have a reference figure with which to use the actual readings from the PJ.
So Temp 2 won't vary greatly if the fan is on low, medium or high (obviously, as the PJ runs for a while, heat from the bulb unit will increase the tmep around the sensor).
If you don't believe me about the inverted readings, enter service mode - self check, note the Temp 2 reading & then breathe slowly a couple of times into the air intake. The temp displayed will drop a couple of degrees!(actual temp is increasing)
I'll open up my unit some day to check where the Temp 1 NTC (or maybe it's a PTC, but I doubt it) is located, but it's most likely in the exhaust outlet area.
Again, in the service menu, check your temps in low (default) fan speed mode, then increase the fan speed to high (or even normal) & watch the temp 1 figure increase. Obviously the temp is decreasing, but the indicated temp is increasing. This again confirms the readings are inverted.
Also, if you're very quick to check the temp readings immediately on startup, you'll see that Temp 1 & Temp 2 are almost identical, but as the bulb, & consequently exhaust air, heat up, temp 2 stays pretty much the same, but Temp 1 decreases (indicating an increase in exhaust air temp).
I've 180hrs+ on my unit, running in Eco mode with low fan & no problems. These Mercury vapour lamps do run extremely hot, but I'm not unduly concerned about temperatures on this unit. Plenty of failsafes if the fan should cease/slow or the intake/exhaust be obstructed.
I'm currently looking at reducing the noise output of this PJ with some simple modifications & maybe the use of a different (more efficient/quieter) cooling fan.
BTW, I'm an engineer, so I have at least some knowledge about these matters.:cool: