PowerMac7,3 - Full Speed Fan Issue?

[FineFuturity]

Hi all!

I recently got my hands on a PM G5 DP and while it works wonderfully, the fans seem to be running at full speed. I've tried NVRAM resets through Open Firmware, SMU resets by pressing the little button on the logic board, running thermal calibration with ASD 2.5.8 (more on this below), changing the processor settings in System Preferences... and I'm running out of ideas.

Something to note: when I run the Thermal Calibration on ASD, it gives me a "CPU Fan Intake Error" and to check that the plastic shroud is seated correctly. It's definitely seated correctly and have confirmed the sensor detects when the door is off (red LED comes on when removed and goes off when reseated). I'm wondering if it's another sensor somewhere failing or if something isn't plugged in.

I should also add it does have a graphics card and a TV tuner occupying some slots on the logic board. Was thinking about taking those out and reseating them, but at that point, I'm just throwing things to see what sticks.

Any help?

 

[B S Magnet]

Hi all!

I recently got my hands on a PM G5 DP and while it works wonderfully, the fans seem to be running at full speed. I've tried NVRAM resets through Open Firmware, SMU resets by pressing the little button on the logic board, running thermal calibration with ASD 2.5.8 (more on this below), changing the processor settings in System Preferences... and I'm running out of ideas.

Something to note: when I run the Thermal Calibration on ASD, it gives me a "CPU Fan Intake Error" and to check that the plastic shroud is seated correctly. It's definitely seated correctly and have confirmed the sensor detects when the door is off (red LED comes on when removed and goes off when reseated). I'm wondering if it's another sensor somewhere failing or if something isn't plugged in.

I should also add it does have a graphics card and a TV tuner occupying some slots on the logic board. Was thinking about taking those out and reseating them, but at that point, I'm just throwing things to see what sticks.

Any help?

Offhand, have you examined whether the CPU intake fan assembly is seated correctly in its (short) track and socket? Sometimes, you can feel a soft click as this piece seats in properly. When it isn’t seated in there properly, the flat pull handle on the assembly might not rest flush and either one or both of the fans might not be running (or running intermittently). I’ve run into this particular issue when dealing with routing SATA cables from a PCI-X card in my setup, when one of the cables is just enough in the way that a full seating of the intake fan assembly isn’t possible.

Also, I’m not sure if yours is a single- or dual-CPU model, but check to see that the two fans in that intake fan assembly are both spinning at all times. They tend to run, nominally, at a rate of about 300rpm, so while they don’t generally look like they’re moving ridiculously fast, they should always be turning when the system is powered up.

 

[FineFuturity]

Offhand, have you examined whether the CPU intake fan assembly is seated correctly in its (short) track and socket? Sometimes, you can feel a soft click as this piece seats in properly. When it isn’t seated in there properly, the flat pull handle on the assembly might not rest flush and either one or both of the fans might not be running (or running intermittently). I’ve run into this particular issue when dealing with routing SATA cables from a PCI-X card in my setup, when one of the cables is just enough in the way that a full seating of the intake fan assembly isn’t possible.

Also, I’m not sure if yours is a single- or dual-CPU model, but check to see that the two fans in that intake fan assembly are both spinning at all times. They tend to run, nominally, at a rate of about 300rpm, so while they don’t generally look like they’re moving ridiculously fast, they should always be turning when the system is powered up.

Can confirm the fan intake sits flush and that both fans are indeed running. In fact, all the fans are running as they seemingly should.

EDIT: Another issue I found is the system refuses to sleep.

 

[mustagcoupe]

For some bizzare reason apple wired the sensor so unplugging it makes the computer think the fan shroud door thing is properly in place. you could try unplugging the sensor harness from the computer and see if that fixes it. If it does you have a wire or sensor problem. It should be the 8? pin connector at the top back of the board. There are 2 similar connectors. One is for the rear fan and is closest to the back, the 2nd one from the back with all the very thin wires coming out of it is the correct one.

EDIT: Sometimes the sensor does not trigger all of the fans to run full speed. Sometimes it only triggers the one in the cd drive bay while still indicating an intake fan speed error. Its very confusing and i do not know why apple did that.

 

[FineFuturity]

For some bizzare reason apple wired the sensor so unplugging it makes the computer think the fan shroud door thing is properly in place. you could try unplugging the sensor harness from the computer and see if that fixes it. If it does you have a wire or sensor problem. It should be the 8? pin connector at the top back of the board. There are 2 similar connectors. One is for the rear fan and is closest to the back, the 2nd one from the back with all the very thin wires coming out of it is the correct one.

EDIT: Sometimes the sensor does not trigger all of the fans to run full speed. Sometimes it only triggers the one in the cd drive bay while still indicating an intake fan speed error. Its very confusing and i do not know why apple did that.

Oh, that's really... odd. Either way, just unplugged it and am re-running the Thermal Calibration with the ASD now. Will report back with what I get.

 

[FineFuturity]

For some bizzare reason apple wired the sensor so unplugging it makes the computer think the fan shroud door thing is properly in place. you could try unplugging the sensor harness from the computer and see if that fixes it. If it does you have a wire or sensor problem. It should be the 8? pin connector at the top back of the board. There are 2 similar connectors. One is for the rear fan and is closest to the back, the 2nd one from the back with all the very thin wires coming out of it is the correct one.

EDIT: Sometimes the sensor does not trigger all of the fans to run full speed. Sometimes it only triggers the one in the cd drive bay while still indicating an intake fan speed error. Its very confusing and i do not know why apple did that.

Still getting the same error on the ASD. *head desk*

 

[mustagcoupe]

Did it make the fan stop screaming when you unplugged it and booted into mac os. Im not sure it will pass thermal testing with the sensor disconnected and the fans always run full speed in ASD. If disconnecting the sensor header did not do anything to change the fan speed its probably not the sensor or cable. But if disconnecting the sensor and booting into mac os made the fan speed normal you probably have a bad sensor or wire.

 

[FineFuturity]

Did it make the fan stop screaming when you unplugged it and booted into mac os. Im not sure it will pass thermal testing with the sensor disconnected and the fans always run full speed in ASD. If disconnecting the sensor header did not do anything to change the fan speed its probably not the sensor or cable. But if disconnecting the sensor and booting into mac os made the fan speed normal you probably have a bad sensor or wire.

Booted into Tiger to double check and the fans are still running high, but sleep is now fixed. So guess it is a bad sensor/wire?

 

[mustagcoupe]

Maybe. G5s are hard to diagnose. It seems like even apple themselves had problems diagnosing g5s from old threads ive read. There are also 2 sensors on that cable. One for a temp sensor in the drive bay and one for the fan duct door sensor. You have to remove the power supply to get to the door sensor itself. The temp sensor could be screwing with the thermal calibration as its also unplugged. The only reason i even know about that sensor plug and its behavior is some trouble i had building my plywood g5. Some of the behavior you get when screwing around with g5s is kind of insane. To me it really feels like the development was extremely rushed or done somewhat incompetently. Like the sensor that thinks its working when unplugged is the opposite of everything else ive ever heard of and seen. And i noticed that once the g5 is fully working and calibrated you can unplug some of the fans and it will pass diagnostics as if they are still plugged in. Its very odd, that sort of thing should not be happening. On a physical design level that fan for the u3 northbridge heatsink is just idiotic. It works but not nearly as well as it could, a small squirel cage fan sucking not blowing air through a very poorly sealed duct is not a great design in my opinion. I like G5s but i feel like apple should have spent a bit more time making sure the diagnostics and sensors arent buggy.