L400 BIOS downgrade solves temperature sensor and fan control issues!
Ladies and gents it’s true: downgrading the bios from A09 or A08 to A06 solves the fan control issue and restores temperature sensor functionality (ie ACPI works again)!
What does it mean? The L400 can behave as it was supposed to: turn on the fan when it’s hot and turn off the fan when it’s cool enough. No more constant running, horrible horrible fan noise! Also the temperature sensor gives more or less proper readings to for example Speedfan ; temperature (at 700MHz) varies around 48-55 deg. C, around 40-45 at 500MHz.
To check your BIOS version: start the computer and press F2 to enter bios where it shows the version.
To downgrade: download L400A06.exe from Dell’s FTP: Run it and follow the instructions to create a floppy disk and reboot the L400 with it inserted. Follow instructions. After it says it’s complete and leaves you in A:, type l400-a06 /forcemode. It shows a progress window and after a while it reboots and the bios is now downgraded to version A06. Remove the floppy otherwise it will just boot from it again.
Up or downgrading the the BIOS is done at your own risk! Always use AC power (not just battery) when up or downgrading the bios.
The effects of these restored functions on the choice of fan remains to be determined. The 40mm I mounted in an earlier post is a 2-wire fan while the stock is a 3-wire with pwm (speed control).
Edit: The downgraded L400 can start and stop the fan as it should even when using a 2-wire fan. Yay! For those on the lookout for a 3-wire replacement fan I came close to buying a Revoltec airguard 40mm (40x40x10). It should be fairly easy to modify to fit in the L400. The 2-wire fan I use is a Revoltec, part of a chipset-cooling kit.
Edit 2: March ’09 … Just thought I’d say that the only reason I haven’t posted for quite a while is that with the BIOS finally working (A06) and a silent fan installed – the L400 is humming along as it should. Doesn’t really make for an exciting new post if you know what I mean 
. Anyway, I hope you’ll find something useful here, cheers!
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Hello,
A friend gave me a L400 a few weeks back and found this blog very useful. I’ve gotten xubuntu installed on it and pushed the bios back to A06 thanks to your help.
Quick question, have you looked at diabling ACPI and using APM instead (http://ubuntuforums.org/showthread.php?t=2620 using the info in post 3)? I had to do this when the bios was still A09 to keep xubuntu from suspending all the time. I know with my L400 APM runs the fan more consistantly with APM meaning a cooler laptop. The only downside I’ve found is suspend doesn’t work, just hibernate.
I may go back to ACPI if I can configure the fan activation points. With ACPI, the fan doesn’t kick-on until the tempreture reads 70+ degrees C (too hot for my likeing).
Hello Michael.
Thanks! It’s great to hear that the blog is useful.
Re ACPI or APM – I have not, but only due to my own lack of experience with Linux. That’s a great tip for serious Linux users out there though! You’re very welcome to report any findings that can help make the L400 better to work with.
Thanks for the page, short, to the point, far more useful than the rest of the pages and pages of waste ads and fake refer links..
Thanks Rob!
I had a quick question. Would there be a way I can rotate the display of my L400 running Windows XP?
The idea is to mount my L400 to the bottom of my kitchen cabinet and rotate the display so that it looks like a flip down DVD Players we see in many Vans.
I plan to have a wireless keyboard and mouse on my countertop.
Any advice would be highly appreciated.
Sudhi
[Moved from other post due to layout difficulties.. l400modblog]
Hello Sudhi!
I’m not sure exactly how you want to physically mount it, but here are my thoughts:
There’s very little “slack” in the cable connecting the display to the motherboard, if you want the screen in a new angle towards the rest of the l400 you’re looking at a very small possiblity. The easiest way to check is just to try removing the display for yourself to see what you can do, it gets pretty boring screwing and unscrewing… but you’ll know for sure.
Perhaps you mean rotate in the sense of making the screen lie face up when the l400 is folded together? This could work cable-wise but you would get a very messy, open area where the display used to sit as it can no longer be mounted in a normal way to the rest of the computer.
I hope some of this helps… just get your screwdriver and start testing!
Thanks for this. I was looking for a “Software Solution”. Eg. I have a HP NC6400 with XP-SP3 running on it. If I press CTRL+ALT+Down Arrow key, the display rotates 180 Deg! Yipee. That’s what gave me the idea of doing the same with the L400. But alas, the display drivers did not allow that I think. Still researching on the web if there is a Software which can accomplish that.
Thanks for the inputs though.
Regards
Sudhi
Hello, I’m trying to downgrade my L400, I’ve got a DOS HD that I Can use (tried to use a cf card W/ usb adaptor but failed to boot) however I can’t figure out how to get it to spit out the files I need to actually do the flashing, I have no floppy drive anymore.
No joke, I’ve lost it since Ive been using my cf card, and or thumbdrives. (my trusty jumpdrive went dead over a couple months ago… definatly got my use/worth out of that lil 512mb stick though ;P )
Anways if you could email me a floppy image, using dd, or in a compressed file, w/e is easiest, that would be great
Thanks for the info
I may see about getting a touchscreen and flipping my screen around as well… I have no keyboard for it, it died… only extranal one now…
Hello Tom!
You might be able to find cheap spare parts on ebay and the like, but I’m sure you know that already.
It sounds like quite a work in progress… good luck!
Hi,
Great website !
I have downgraded my Bios from A09 to A06 and speedstep works as it should, thanks !
I had a spare dvd rw from a broken laptop so I removed the 24x cd-rom and installed it. It works great but the front bezel does not match(not really a problem). Model is Optiarc DVD RW AD-7530A.
I tried upgrading the ram from 128mb to 256mb but it only recognises 128mb for some reason ? the ram is 256mb pc100 cl2. I tried 2 different sticks but still only recognised as 128mb. Any ideas ?
Cheers,
Paul.
Hi Paul!
(I took the liberty of moving the post where more people would find it
Thanks for the feedback! Great to hear about the dvd drive, I haven’t come across one myself and wasn’t sure if anything would fit. Thanks for the info.
Re the memory – strange! I just booted mine to check that it isn’t a bios limitation in A06, but my l400 still reports 256mb.
Is it reporting 128mb in the bios or in windows – and if so, what version of windows/other os are you using?
I use a memory I bought from memoryx: 256mb pc100, cl3. Yours shouldn’t be a problem.
I haven’t heard of any memory issues on the l400 before and I think yours should be solvable, you could try resetting the bios if nothing else (both soft (within the bios) and hard (unplugging both batteries). Good luck!
Its reporting 128mb in the bios, and also at the boot screen diagnostics. OS is puppy linux live cd which reports 128mb too
I have tried resetting the bios to defaults if that is what you mean ? I haven’t tried a hard reset yet though so I will try that tonight (fingers crossed)
I have only ran puppy linux off the dvd because I bought my L400 with no hard drive or caddy, not bad for £15 though !
Also bought a latitude LS(I think thats what its called) which uses same power etc so I might try the ram in that and see what happens.
Cheers,
Paul.
*Update
I performed a hard reset last night (batteries out and power disconnected), still shows 128mb ram.
I tried the 2 ram sticks in the Latitude LS and they registered as 128mb as well
therefore I think its probably the ram sticks.
I also installed a 30 gig hdd with puppy 3.01 and it runs quite fast/responsive
but seaamonkey is a little slow, due to ram maybe?
If I can’t get the ram chips to be accepted as 256mb I might get some from crucial.com and if it still doesn’t work return it.
Cheers.
Hi Paul
Well it does sound like it could be the stick itself as the problem was repeatable on a different computer.
I’ve done a quick googling and searched the dell forums but could not find anyone having this problem.
128mb is not a lot these days, even the small distros need more and more cpu and memory power…
Is it a 4200 or 5200rpmhdd? The latter is recommendable as it feels a lot faster.
Btw, that’s a bloody good price for an L400! Good luck troubleshooting the memory problem.
Its a 4200rpm hdd. I found it in the loft so its saved me a few quid
Ideally I would have liked to have used a 5200rpm.
I have a 80gig 2.5 inch sata drive but I don’t think I could use it could I ? some sort of sata-ide adapter ? not really much room in the caddy though !
Crucial.com want £30 for 256mb ram ! I could get some generic cheap stuff off ebay but I don’t wanna buy it and then it doesn’t work in the laptop.
The laptop was bought in a car boot sale from a computer surplus stall. I also got a latitude ls for £7 but its only 500mhz so I don’t think I will do anything with that.
Cheers.
Manny thanks for your informations regarding L400
I downgraded A09 to A06 and the acpi works without any problem
The command is “L400_A06 /forcemode”
I run Ubuntu Hardy on this PC. Everthing works well except that I can’t make a restart (reboot). In this case the system block. I have to make a Exit and restart the system manualy. Have you an idea about the reason and a solution ?
Sorry my site mentionned above is in french
when i tried to ‘downgrade the flash to the A06, I get the blue box window with a bourgundy box that says-
PhoenixPhlash Error
not found latitude System
PRESS ANY KEY TO EXIT
Any work around or hint as to why this is happening?
BTW, thanks for the GREAT blog! what a help to have experienced guys helping us less tech-savvy/inexperienced users
Art
I had a problem with Debian Squeeze after update the last bios version. It was a problem with the hal program and acpi. When I boot everything was ok, but after hal was activate, the sistem was to a automatic suspend without press any button.
This was with Bios A9, I downgrade to A6 and the problem dissapear. I was thinking to change the distro to a bsd system, but this resolved this issue. Thanks, I never would think that downgrade to older bios would resolve something like this.
Anyway the problem started after update from Bios a0 to A9.
I recently got one of these laptops and noticed the CPU fan not turning on, which is how I found this blog.
I did the BIOS dowgrade from A08 to A06, then did a fresh install of Ubuntu 9.10 and the problem has been corrected!
Thanks for the help!
I would also like to point out that with a 40gb hdd and 256mb ram, it runs Ubuntu 9.10 just fine, incase anybody was curious. Everything sofar works as it should. Next I will be looking into PCMCIA wifi cards.
Hello, good to hear that the site is still useful. Good luck with your machine!
I bought a used L400 on eBay. It already has A06, but the fan never comes on. The bottom of the unit gets so hot, the units turns off.
What to do????
Dismantle and check the connections… remove, reseat. Though you could try reflashing the BIOS for kicks I suppose. Good luck
I ended up returning the laptop for a refund.
I bought another used L400 on eBay. BIOS is only A01. I don’t have a floppy drive, only the media cable and CD.
Is it possible to upgrade the BIOS using the CD drive?
Answering my own question, I was able to create a bootable CD-RW and upgraded the BIOS on my L400 from A01 to A06. If anyone is interested, please email me.
WOW! How?
Linda,
I have found that it is not possible to use a CD drive, nor a USB memory.
I have (had) both the L400 and the C400 and neither can be BIOS up or downgraded without a floppy drive.
I THINK the reason is that it is not possible to assign the CD drive the usual B drive assignment that the floppy is usually assigned.
Since I was not able to overcome that issue, I can not say if it is possible to use a CD/DVD drive if it is recognized as the B drive.
Still the real reason I say no, is because ALL attempts to use a CD/DVD drive came back telling me that there was NO floppy connected.
No matter the letter, the system recognizes WHAT type of drive it is and it wants a floppy
Arthur,
It is possible to do, and I did it.
http://techplusnj.com/L400_BIOS_upgrade.txt