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Compaq D300 Overheating

Need help with an intruiging problem:
Called to a client  site which has a Compaq D300 which is overheating;

When the machine was powered on Not one of the 3 fans were working; ie Power supply fan, Chassis fan, and CPU Fan;  (client had installed an additional low powered extractor fan in one of the chassis expansion slots but this was not strong enough)

Then the Basic problem was that after a period of time the chassis internals (CPU)  got  hot and a message came up on the screen and performance degraded

I thought  I had some type of PSU issue or maybe a motherboard config problem or maybe a BIOS issue.

Checked the BIOS: Could Not see anthing amiss

Checked the power supply and concluded that given that all peripherals were powered and Motherboard was powered that  most likely there was not an issue here;

The fact that all three fans were not working did seem too coincidental and lo and behold in the middle of all this investigated and observation the fans kicked in and started up;

Now that leads me to a conclusion that there may be some faulty thermo control on the motherboard that randomly kicks in;

Could the root of this be a faulty motherboard and if so how can I determine what the fault is.
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Callandor
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Check in the BIOS for a temperature alert setting that may be set too high.  I never heard of a motherboard that implemented it outside the BIOS.
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Have been through all the settings on the BIOS and could not see anything related to Temp alert or temp settings.

Have also checked on Compaq support site to see if they had anything but no joy;

Will try that source again;

I did see a note here about a 3-pin connector for board control of the power supply fan: http://www.power-on.com/compaq.html.  That would be consistent with other motherboards which allow fan control in the BIOS.
Do you think that if the PSU was faulty and if overheating over a period of time would cause the intermittent activity of the Fans coming on when temp reached a specific point. The fact that all 3 fans come alive at the same time leads me to think that there is some setting or switch that needs to be tweaked.

Also Will get back to client and get the part no of existing PSU to see what the equivalent would be and if I can source locally.
Thx for input so far
Yes, there is a temperature sensor in the power supply if you have a 3-wire fan control cable coming out of it.  If the sensor is faulty, this can lead to improper fan activation.
if those 3 fans are connected to the 4-pin molex connectors, they come straight from the power supply, which should be faulty then. --> try another one
Have finally spoken to client;

The PSU part number is 243890-001 and as luck would have it He was having the problem just as I called; He told me that as he was reading the serial number for me all 3 fans had in a period of micro stop/go (as if the were being triggered) for a period of about 2 mins before they cut in.

The chassis fan and processor fan are powered direct from connections on the motherboard.

I also extracted the following from the Technical reference guide from the Compaq Support site for the D300
http://h20000.www2.hp.com/bc/docs/support/UCR/SupportManual/TPM_329001-001_rev4_us/TPM_329001-001_rev4_us.pdf

Section 4.7.4  of which states that there is an ASIC which monitors a thermal diode which is internal to the processor
My reading of this would suggest that given the displayed symptons, this could be  be root cause ie faulty diode within processor

Resolution : get a replacement processor or system  

Do you agree??

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