Temperature Sensor Readings and Fan speeds

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Temperature Sensor Readings and Fan speeds

I'm having an issue with the fan speed for the CPU staying pegged at 3500RPM. I have done the SMC reset, PRAM reset, and don't know what the next is.

All the temperature sensors are showing well within normal levels in comparison to another mac of same vintage. There are no missing sensors, and none showing wacky values.

There is an error in the Apple Hardware Test with the Failure code: 4SNS/1/40000000: TL0P

The machine starts up just fine with the exception of the CPU fan pegging at 3500RPM. The DVD drive fan is 900 RPM and the Hard drive fan is 1200 RPM plus or minus.

IMAC Mid 2007, Mac OS X (10.5.7)

Posted on Jul 19, 2009 12:40 PM

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Answer 1

den.thed

Level 10

91,576 points

Jul 19, 2009 4:15 PM in response to jrhus12

Hi jrhus12

Welcome to Apple Discussions

I would again reset the SMC exactly as described in > http://support.apple.com/kb/HT1543

especially note step # 4 +Plug the power cord back in, making sure the power button is not being pressed at the time. Then reconnect your keyboard and mouse to the computer.+

Then I would try another sensor monitoring program, it is possible that the one you are using may not be reading all the sensors in your iMac.
http://www.bresink.com/osx/0TemperatureMonitor/details.html
http://www.apple.com/downloads/dashboard/status/istatpro.html

Your best bet for finding out what that error code means, is to call your Local Apple Service Provider or Apple Store and report that code to a tech.
http://www.apple.com/buy/locator/service/

Dennis

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Answer 2

jrhus12 Author

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Jul 19, 2009 5:23 PM in response to den.thed

Thank you for the reply.

I used the istatpro utility to read the values and compared them with a working imac of same vintage and they are close. The imac with the CPU fan pegged had lower temperatures since it was getting 'overcooled' The CPU temp for example is 35 C. The Highest temperature is the HD bay, and the GPU.. and they are only 41C.

One thing i did try, hoping it would 'reset' the SMC/sensors/fan controllers was to do the step where you hold the power button and plug in power. This sent ALL the fans to maximum speed.

After that test, I then did the steps described in the support document, and the HD and DVD fans returned to normal speed. The CPU fan was still sitting at 3500RPM. Bottom line is still the same problem.

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Answer 3

den.thed

Level 10

91,576 points

Jul 19, 2009 6:37 PM in response to jrhus12

The iStat Pro widget is not reading and reporting the stats of all the sensors in your iMac, there are other temperature sensors besides the CPU sensor that controls the CPU fan.

Try the Temperature Monitor. > http://www.bresink.com/osx/0TemperatureMonitor/details.html

To be more clear, only an Apple tech. can tell from the error code which sensor is bad.

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Answer 4

jrhus12 Author

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Jul 20, 2009 4:50 AM in response to den.thed

I used the program you referred Temperature monitor you referred to to capture this information. These numbers below are right after starting the imac. I guess there is something more that is hidden as the CPU fan is still pegged at 3500RPM.

I will be calling apple i guess to find out where it thinks there is a problem.

2009-07-20 07:46:53 -0400

Ambient Air: 20.0℃
CPU A Heatsink: 30.0℃
Graphics Processor Chip 1: 33.0℃
Graphics Processor Heatsink 1: 31.0℃
Graphics Processor Temperature Diode: 35.0℃
Hard Drive Bay 1: 29.0℃
Memory Controller: 29.0℃
Optical Drive: 25.0℃
Power Supply Position 1: 32.0℃
SMART Disk WDC WD10EADS-65L5B1 (WD-WCAU4A565108): 26.0℃
Wireless Module: 33.0℃

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Answer 5

den.thed

Level 10

91,576 points

Jul 20, 2009 4:40 PM in response to jrhus12

For more info, see the Google Search: [4SNS/1/40000000|http://www.google.com/custom?hl=en&client=pub-6263300333013957 &cof=FORID%3A1%3BGL%3A1%3BLBGC%3A336699%3BLC%3A%230000ff%3BVLC%3A%23663399%3BGFN T%3A%230000ff%3BGIMP%3A%230000ff%3BDIV%3A%23336699%3B&ie=ISO-8859-1&oe=ISO-8859- 1&q=4SNS%2F1%2F40000000&btnG=Search]

As I scanned thru the hits most accounts where for MacBook Pros, but there are a couple on the first two pages that stand out:

http://www.xlr8yourmac.com/feedback/2009iMac_fannoise.html
http://discussions.apple.com/thread.jspa?threadID=2019248&tstart=0

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Answer 6

jrhus12 Author

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May 25, 2010 3:27 PM in response to jrhus12

turns out TL0P indicates LCD temperature sensor problems, and not problems with the Logic board in my case. Replacing the damaged LCD temperature cable solved my problem!

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