Agie HSS error

Unfortunately questions about this machine are becoming common. We are getting error massage 705. The manual describes it like this.

Message: 705
Meaning: Temperature AGIPULS HMC >50°C
Measures: Is air filter clean? Ambient temperature too high? Call Service.
Source: A PM1 P9
Circuit diagram: HSS:8

That led to the board pictured below. We found an IC chip that looked fried and replaced it but that didn't change anything. The top red LED on the board is not lit and the fans in the bottom of the cabinet are not running (they get power from that board) but I don't remember if they were always on or not. It looks like there are 3 thermocouples sticking out of the board. It was definitely not >50°C there.

The fans in the door never run. the four boxer fans below the PMOs should all be running! not that this is your problem. Are the 2 bulbs working on the outside of the cabinet? it been a while but i seem to remember if the white ac one was out you got the message

The other fans in the cabinet seem to be running. Both the bulbs on the outside are good, and the white one lights up when the machine is powered on. The error shows up pretty much immediately when the operating system loads so I'm pretty sure nothing is actually over temp.

Edited to add: After some testing, what I thought were thermocouples are actually thermistors. The resistance across the three are not the same, but the resistance of all of them decrease with increasing temperature.

ill look at prints in the AM

I did some testing today with a heat gun to try and narrow things down a bit. After powering the machine up, the lower two LED's are lit and the top one is off. If I heat the top thermistor the top LED comes on and the fans in the door begin to run. If I heat the lower thermistor the lower LED goes out and error 704 appears (704 is also a temp error, it trips at 45°C instead of 50°C). If I heat the middle thermistor the middle LED goes out but nothing else changes. This leads me to believe that the middle thermistor/LED is responsible for error 705, but it appears that the board is working correctly and whatever that board is talking to may be where the problem lies.

do you have prints for HSS cabinet?

Unfortunately no, the machine came with the manual, but none of the electrical schematics.

Looks like I was wrong about the board working correctly. The voltage signal coming from that board should have been nominally 24V and it was more like 5V. I was able to get another board to test with and it worked fine.