What is the purpose of Ambient board sensor

[basilt]

hello, my mac is in an environment without heating and recently the temperature dropped down to 19 degrees celcious.

i have a g5 2ghz DC, and when i push the start button it does not make chime at all,
starts up, then top and back fans speed up fast, very noisy and thats it.

Some days ago, when i was working, the red light on pcb under memory (sits alone on the motherboard, but close to the DIM less, switched on Red, then mac stopped operating (no movement on screen)

I removed, plugged ram in room temperature, restarted ok, then moved mac back to the colder environment and does not startup.

Does this Ambient board has anything to do with the spinning fans and G5 not booting from HDD's ?
Hdds are ok, ram is ok…. what is wrong ?

 

[Eriamjh1138@DAN]

According to my G5 Service manual, the 7th LED from the top, inset below the DIMM slots, is LED #7.

ON RED indicates a CPU hang.

Things to Check: Check RAM. Is processor assembly seated properly? Check that mounting screws are properly tightened.

Remove processor assembly and check for damaged pins on processor connector or logic board connector. Replace processor, if necessary. Replace logic board, if necessary.

Since you already seated the RAM, try removing pairs until you find something that works consistently.

 

[basilt]

although i reseated ram, started testing it, and for a reason some restarts showed less ram than i have had. Then with the addition of new pieces i am back with 10gb again.

possible cause might be the temperature rather than ECC and non-ECC ram combination. I put the ram in new order, it started normally, but when i moved to the colder environment (non room temperature) the mac started freezing again, Led7 lights briefly, then goes off and fans spin, after 2-3min fans speed is very fast.

I wait for the snowstorm to end, and see if i have a better luck in restarting normally.

the CPU never had problems, so i dont think i should bother checking for problems.

 

[Eriamjh1138@DAN]

In my experience, temperature-related problems are due to failing solder joints and connections. The thermal stresses over the years have compounded to micro-cracks and can cause these annoying intermittent failures.

I don't think you should combine ECC and non-ECC ram. Isn't that a big no-no? I recommend trying one or the other and see what happens.