Just adding some words, parroting what Elli told me: this temperature sensor (RTD) is nominally supposed to be on "the" viewport (HAM4? Some BSC? The Injection port for the laser? Dunno). This sensor is not mounted on the viewport currently, it's mounted on "the" chassis, which (I believe) resides in the TCS remote racks by HAM4. She's seen this in the past: even looking at this sensor wrong (my words, not hers) while you're cabling / electronics-ing near HAM4, this sensor trips. As she says, this was noticed and recovered by her before it became an issue with the IFO because recovery went much slower than anticipated.

If I understand correctly the sensor I think your talking about then yes this should be on the viewport (the BSC viewport which the laser is injected in). The viewport sensor though is an IR sensor, but for some parts of the wiring in the control box (and thus on the MEDM screen) the IR sensor and RTD sensor are wired in together making it hard to know which one caused the trip.  Its supposed to monitor scattered light coming off that viewport. It is very sensitive and can be affected by humans standing near it, light being shown onto it (one of the ways to set the trip level is to hold a lighter up to it ), maybe also heat from electronics, etc. So just sitting in the rack I am not at all surprised that it is tripping all the time and causing grief.

My suggestion is to try to get this installed on the viewport if you can, otherwise if you can’t and it really is causing problems all the time, there is a pot inside the control box which you can alter to change the level at which it trips.