Powermac G5 Fans Racing Mystery

breeves002

macrumors newbie
Original poster
Feb 17, 2010
12
0
St. Louis
So I just replaced the motherboard on my June 2004 Dual 2.0GHz Powermac G4 due to three blinking lights indicating bad memory but it was really the dumb BGA chip on the underside of the board.

Anyways everything works, but the fans race. When I boot to Apple Service Diagnostic and try to do the thermal calibration it gives me two errors that are identical for both CPUs. The error reads "check or replace temperature inlet sensor on housing."

Now this is just weird because nothing changed from one motherboard to the other so I'm just scratching my head.

If I leave the plastic air deflector in place the expansion slot and all 4 CPU fans race. If I remove it those fans go down to normal levels and the HDD fan races (red light turns on). I find this VERY confusing.

Any insight into this would be great!

I've tried:
-Resetting NVRAM
-Replacing PMU Battery with known good
-Resetting PMU

I feel like I've done other things I forgot too. I'm thinking this motherboard is from a 2003 model not a 2004 model which my CPU's are from. Will this cause an issue?

Thanks!
--
Sam

MacBook Air 2011 - i7/4gb/256gb SSD
MacBook Pro 2010 15" - i5/8gb/256gb SSD
PowerMac G5 Late 2005 - Dual Core 2.3/8gb/500gb
PowerMac G5 June 2004 - Dual Processor 2.0/5gb/160gb
 

Altemose

macrumors G3
Mar 26, 2013
9,089
444
Elkton, Maryland
So I just replaced the motherboard on my June 2004 Dual 2.0GHz Powermac G4 due to three blinking lights indicating bad memory but it was really the dumb BGA chip on the underside of the board.

Anyways everything works, but the fans race. When I boot to Apple Service Diagnostic and try to do the thermal calibration it gives me two errors that are identical for both CPUs. The error reads "check or replace temperature inlet sensor on housing."

Now this is just weird because nothing changed from one motherboard to the other so I'm just scratching my head.

If I leave the plastic air deflector in place the expansion slot and all 4 CPU fans race. If I remove it those fans go down to normal levels and the HDD fan races (red light turns on). I find this VERY confusing.

Any insight into this would be great!

I've tried:
-Resetting NVRAM
-Replacing PMU Battery with known good
-Resetting PMU

I feel like I've done other things I forgot too. I'm thinking this motherboard is from a 2003 model not a 2004 model which my CPU's are from. Will this cause an issue?

Thanks!
--
Sam

MacBook Air 2011 - i7/4gb/256gb SSD
MacBook Pro 2010 15" - i5/8gb/256gb SSD
PowerMac G5 Late 2005 - Dual Core 2.3/8gb/500gb
PowerMac G5 June 2004 - Dual Processor 2.0/5gb/160gb
It may very well be the Ambient Temperature Sensor on the main Logic Board! If I remember correctly it is a part up by the internal speaker. You should be able to transfer it from the trashed board to the new one without any repercussions.
 

DeltaMac

macrumors G3
Jul 30, 2003
9,589
2,349
Delaware
If you have some difficulty identifying that ambient board, it's a tiny circuit board, maybe 2 x 3cm that plugs in directly to the logic board, on the edge near the speaker/fan assembly.
 

breeves002

macrumors newbie
Original poster
Feb 17, 2010
12
0
St. Louis
I already threw away the old motherboard. I DID however salvage this sensor. I can't find anywhere to plug it in on this new motherbaord. I have a 1.6GHz single as well and there is no where to plug this sensor in on that board as well. I do remember where it went on the old dual 2.0.
 

breeves002

macrumors newbie
Original poster
Feb 17, 2010
12
0
St. Louis
No worries. I hope that it helps the OP, as there are differences between the 2003, 2004, early 2005, and late 2005 models, and mixing components could cause havoc.
Well that solves it most likely.

I need to figure out what I did with that little thing when I pulled it off the 1.6GHz board. 2003 models use the little cable thing and 2004 use the little card!

I'll keep you updated.


If I have to buy a new cable this says its for 2004-2005 and this motherboard is a 2003 I'm 99% sure. Will this work? http://www.ebay.com/itm/Apple-922-6205-PowerMac-G5-Thermistor-Cable-2004-2005-/390277309663?pt=US_Computer_Cases&hash=item5ade5724df
 

AmestrisXServe

macrumors 6502
Feb 6, 2014
263
1
The 2003/2004 models use the thermistor cable, and the 2005 models use the ambient board.

You need to be certain that you have the correct part.
 

AmestrisXServe

macrumors 6502
Feb 6, 2014
263
1
The 2GHz models are essentially identical between 2004 and early 2005: I believe that some, early 2GHz systems may have used the thermistor, but most use the ambient board, and that carried over to the later models.
 

Intelligent

macrumors 6502a
Aug 7, 2013
924
2
So I just replaced the motherboard on my June 2004 Dual 2.0GHz Powermac G4 due to three blinking lights indicating bad memory but it was really the dumb BGA chip on the underside of the board.

Anyways everything works, but the fans race. When I boot to Apple Service Diagnostic and try to do the thermal calibration it gives me two errors that are identical for both CPUs. The error reads "check or replace temperature inlet sensor on housing."

Now this is just weird because nothing changed from one motherboard to the other so I'm just scratching my head.

If I leave the plastic air deflector in place the expansion slot and all 4 CPU fans race. If I remove it those fans go down to normal levels and the HDD fan races (red light turns on). I find this VERY confusing.

Any insight into this would be great!

I've tried:
-Resetting NVRAM
-Replacing PMU Battery with known good
-Resetting PMU

I feel like I've done other things I forgot too. I'm thinking this motherboard is from a 2003 model not a 2004 model which my CPU's are from. Will this cause an issue?

Thanks!
--
Sam

MacBook Air 2011 - i7/4gb/256gb SSD
MacBook Pro 2010 15" - i5/8gb/256gb SSD
PowerMac G5 Late 2005 - Dual Core 2.3/8gb/500gb
PowerMac G5 June 2004 - Dual Processor 2.0/5gb/160gb
Everyone calls it nvram on powerpc and pram on intel, its intel nvram and powerpc pram, anyways do you think its a problem with the computers or the actual fans?
 

breeves002

macrumors newbie
Original poster
Feb 17, 2010
12
0
St. Louis
SOLVED!

Got the little tiny cable in today. Fixed it!

Fans still raced but I booted to ASD Dual Boot and ran thermal calibration which fixed it. Idles silently now. Very happy with this result.

Thanks for the help!

I have turned my Dual Core 2.3 into my main server running OS X 10.5 Server. The Dual 2.0 is running normal 2.5.8. I actually sold the 7800GT but have the 6800 Ultra in the DP 2.0.

Getting a Mac Pro 1,1 tomorrow. Excited about that one!