Why does fan run but computer won't come on

Older Dell laptop, pwr light on, fan running, that’s it, does not come on. Turn if off, the fan blows 2 seconds, then fan shuts off

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Hi @kansas123 ,

What is the full model number of the laptop?

Does it do this when the charger is connected?

Sounds like the BIOS is corrupted and needs to be reset.

Try the following:

i). Disconnect the charger if connected.

ii). Remove the main battery from the laptop.

iii). Open the laptop and find the coin cell RTC battery on the motherboard and remove it from the motherboard.

Note: remember the orientation of the coin cell battery before you remove it. Usually it is +ve on top as marked on the battery. Once it has been removed, measure the voltage of the coin cell battery. If it is <2.5V DC replace it. Normally it is a CR2032 (marked on battery itself) Lithium non rechargeable battery that is available most everywhere. As you didn’t supply the laptop model number, sometimes this battery may have leads on it and plugs into a socket on the motherboard rather than being held in a battery holder so just unplug it instead.

iv). Press and hold the laptop’s Power On button for a full 15 seconds and then release it.

v). Reinsert the RTC coin cell battery on the motherboard.

vi). Re-assemble the laptop and reinsert the main battery.

vii). Connect the charger and try turning the laptop on.

If it starts there may be a message about the date and time being incorrect. This is normal as the BIOS has been reset. Once the time and date have been corrected the message won’t appear the next time the laptop is started.

Also check if the battery is charging. If it is allow it to fully charge before disconnecting the charger.


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It is a Dell E6420, 7i core. The battery is wired into the motherboard.... I performed the instructions you sent but it did not start; it acted the same as before. I will try again. Ps, yesterday I took hard drive out an installed it in another laptop (ASUS) I had and it fired right, so I believe you are on the right track. I even put that other drive in the Dell and it acted just like the original problem. So problem is in this Dell hardware someplace. Thanks for your help Jayeff



Here's the service manual for your laptop.

Removing the main battery is straightforward - see p.21

The RTC battery is not mentioned in the manual but the link shows what it looks like and how much it costs etc.

Try starting the laptop with the charger connected but the main battery removed and see if that works.


I did not have any trouble with the main battery, the battery I was talking about is the one inside, which was a plug in, not one that comes out. I will try start the computer with the charger and with the main battery removed an see what happens. Thanks



If that doesn't work you may have to start checking the power supplies on the motherboard to make sure that they're all there and all OK.

The fan and power light may be working but that doesn't mean that power is getting to the CPU etc.

What is the history of the laptop?

Here's the schematic for the motherboard. Verify that it is the one for your model - the motherboard schematic linked here is for a Compal LA-6591P or LA-6593P Rev:1.0. motherboard. This will be printed on the motherboard itself.

If it is the correct one for your laptop model, download the schematic (it's free) and then go to p.44. That the DC DC Interface section of the schematic where it shows all the power supplies.


Ok, I opened it back up and removed that RTC battery so that I could check the voltage, which measured about 3 volts. I will look at the schematic, thanks for that. As far as history, I have had it for about 7 years with virtually no problems. About 3 months ago I had it wiped and was reloaded with Win10. Far as I know it is up to speed on any updates.




Take a look at the RAM and see if that’s properly seated - Dell isn’t exactly good about proper RAM POST errors on the pre-3L (low power 1.3V) systems with cheap/mixed RAM, even today in some cases. The problem with your laptop is the E6420/30 is not known to have tight tolerances on RAM errors in some cases. Yes, the DDR3 1.5V Dells can take cheap RAM all day to the point you can buy unused generic Chinese RAM on eBay for nothing, but if it has an issue and there's poor communication you get this issue so you need to know to watch for unusual POST issues if you do it. Yes, I mixed brands in my 768p 7490, but I used two Dell OEM’d modules to help the odds, and I know I need to watch it for issues.
Thankfully they started to clamp down on garbage RAM (and better communicate RAM failures, or just block POST with RAM that has no business being used because it’s that bad) with the HSW series (5/6X40, DDR3L required per Intel) and subsequent HSW era AMD laptops due to this crappy RAM causing issues with decreasing tolerances, and got really strict on some of the DDR4 models (Skylake-present) - in some cases, you can't even mix DDR4 RAM modules with Dell unless the specs are identical! This poor reporting issue is the exact reason (even today!) machines like the 6420/30 still sell, albeit not for much. If you know about this problem and use quality RAM, it often wakes them up and you just got a cheap laptop.
Sometimes they’re won through joke bids, but others need the machines and if it has the signs of cheap RAM causing issues some people gamble if it’s not hard to access.

Start with the RAM - get a good set of Crucial/Micron (Crucial OEM), or even Kingston and Teamgroup and start there. If you already have multiple modules, pull both and put one in at a time on slot A (lower slot) and see. Some Dell laptops are real particular about using Slot A (sometimes known as Slot 0) first.


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