This morning while in the CER for other reasons, I heard a coil driver on HAM4 ISI making a ticking/chirping noise. Fil suggested this was probably a fan, so we've pulled the chassis to check it out. We've put in a spare and will run that until next maintenance probably.
Chassis pulled is S1100320, the spare we put in is S1103567. Frs is https://services1.ligo-la.caltech.edu/FRS/show_bug.cgi?id=35547
We swapped the old chassis back in yesterday, after Fil replaced the fan last week.