XPS420 CPU Fan Speed Control - New to the Community Forum - New to the Community - Dell Community

XPS420 CPU Fan Speed Control

New to the Community

New to the Community
Having trouble deciding where to post? Get tips and recommendations here.

XPS420 CPU Fan Speed Control

  • DELL on-site support over three visits changed the HDD fan, CPU fan and now the motherboard, the CPU fan still runs up to max speed from a cold boot and remains there with CPU running 3-4% and 47'C and GPU at 35% fan and 53'C. User situation is intolerable with the continuous fan noise. Mechanically all fans are OK except the CPU fan speed control being the original reason for calls to DELL support.

    Observed when all external USB accessories and network HUB are powered up, the XPS momentarily 'appears to start' then "turns-off' until the power button is manually pressed. Then boot proceeds normally and before I log on the CPU fan is at max speed. Do I assuming this observed momentary power-up causes some BIOS glitch? Does the Wake-on-LAN cause some glitch but after deactivating in BIOS no solution was achieved. I have found if the PC is placed into hibernate, then restarted this sets the CPU fan back to it's slower setting remaining there after many hours of use - as it did when the PC was purchased.

    So where does one go now for the PC still under warranty??  All input gratefully received -thanks

  • The power on is not working correctly, however there may be a USB power overload that is causing the irregular power up.  Devices draw power from the USB hub and depending on how much power or initial power devices draw could be causing the initial power on failure.  I don't know what all you have connected but since it apparently does not do that with the USB devices connected I would suspect eithe the total number of USB devices or one one of the devices is causing a power on overload.  It will take a little troubleshooting to determine which device it is.  If you have an external USB hub and it is not a "powered" hub (one that has it's own power supply) that could be where the problem is.

    In reference to the CPU fan speed, There was a recent post from another user and updating the BIOS fixed that users fan speed problems.  It wasn't the same model PC, but updating the BIOS may be a good place to start.  The current version HERE is A07 and date is 5/7/2009 so it's fairly recent and the new motherboard may not have this version.

    I am not a Dell Employee

    Dell forum member since 2002

    Inspiron 15 - 5577 Laptop

    Home Built Desktop PC with ASUS Z170, i7 6700K CPU,  Windows 10 64 bit Pro. SSD drive.  Sonar Platinum Recordng Software.


    Member of Nashville based R.O.P.E.

  • Thanks fireberd.

    Further to your response on external USB loading, I have not yet tried to disconnect my 1TB Maxtor, Epson R800 printer, HP4300 scanner, Motorola Surfboard broadband modem, a RailDriver console (for Trainz2006 Railway Simulator software).and external speakers.  All these are externally powered and the same hardware since last year, but the issue started occuring over the last several weeks. So I guess this is as you said, divide and conquer the problem accessory. Taking your suggestion further, I removed the 240 volt supply cable to the PC and the Network cable -  then powered up all accesories as normal - then inserted the power cable to the PC.

    I still had the momentary PC power up visible by lights and LCD display, but on manually starting the PC it booted with an audible but acceptable rise in CPU fan speed which then reduced back to what I would consider  'normal'. Has been quiet for the past 4 hours. Apart from this I had performed the AO7 BIOS upgrade last week as suggested for VISTA Ultimate and XPS420 by DELL and other forum commentators as a resolution but to no avail.

    So now it's down to 'plug and power-up' to see which USB accessory or combination of same is causing the issue . Regards from Trainz.


  • Hi fireberd

    Just a vote of thanks and follow up to your suggestion on USB loading and for the many others seemly in the same situation with DELL Fans. Have juggled peripherals and seem to have success. With all these and the PC still fed from the existing SmartUPS 900 only change was to Broadband Modem (was USB) now network HUB and WOL still set to off. Still trying to get SpeedFan utility to register the CPU fans and control same - displays CPU, local and core temps -  but works great on the GPU temp and fan.

    Tried to put the Epson Photo800 printer (was USB) onto firewire port without luck - so much for drivers with VISTA Ultimate - it appears VISTA only accepts input to, not output from the firewire ports. 

    Regards Trainz


  • Hi fireberd
    It would seem a resolution at last with my earlier post and its contained 'joy' a little premature.

    Well time has past and service frustration with DELL has increased with a total of five on-site service calls. After replacement of two Card fans, 3 CPU fans, one mother board and a PSU, DELL finally listened to my PC observations and replaced the processor yesterday. The root cause of the fault was the processor with core 4 running at 13-14 Celsius while the other three cores running at around 30-36 degrees Celsius. Now the temperature of all cores is closer together - how this impacted the CPU fan speed controller only DELL knows.

    So anyone with future issues of CPU fan speed control - assuming the PC is not overclocked - at least check out the following:

    • gross variance in CPU core temperatures
    • Does the momentary pre-POST last longer than normal - it’s possibly tens of milliseconds as power is applied prior to manual switch-on. In my fault state this was longer, possibly half a second.
    • When logged in and with the CPU running around 3%, with the CPU fan at maximum speed - does the CPU fan speed audibly slow with any user activity - say a word document or a web browser is opened or other normal activity - then to rise once again to maximum once the document or screen image is presented.

    And for the service support aspect let me offer some advice.

    Push your suspicians and observations with DELL's technical personnel as I finally had to with their Malaysian support staff. Don't let them start the "we'll swap a few parts to see if this fixes the problem" process using their on-site support company (UNISYS in my case). Plus make sure you confirm what spare parts the service technician is to bring, as in my case five service calls to fix a problem, because the technician did not have a full kit of spares for the PC he was to service. Not a good advertisement for DELL and certainly a costly in-warranty repair for DELL.

    Regards Trainz