Question about Dell Latitude C640 Notebook

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C640 Battery runs laptop - a/c doesn't

My laptop runs fine off of a battery, won't run at all from a/c only. When I have both plugged in, it runs off battery only - nothing from the A/C. What's the likely fix?

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  • Anonymous Aug 27, 2008

    Hi, my laptop wont work off AC means only battery, now my battery is dead. Any suggestions would be welcome. Thanks, Dominic



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Verify the ac adapter is ok. I found somewhere else on this board a solution to this same problem. You have to take the computer all the way apart to access the back of the mother board. Just below the external power connection is a black rectangular component with 4 connections to the board. I found a cracked solder joint at one of these legs. I re-soldered it and now it is working great again. If I find the post with the component designator on it I will edit this and post a link. You will need good mechanical and soldering skills as well as the dell service manual to get it all apart and repair it if this is the problem.

Posted on Nov 04, 2008

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Three things that could cause this. 1- power supply, check it for the proper output with an ohm meter. The aftermarket power supplies, such as Tagus, don't work well with Dell machine and will also cause this, 2- bad battery or engaged fail safe, try starting with the supply only, 3- failed power management system on the motherboard. Other than an aftermarket supply, this is most commonly caused by the power management system or PM chip. Unfortunately, a failed power management system or chip is common with these, and the motherboard will have to be replaced in order to fix it.

Posted on Aug 20, 2008


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If your battery does not hold charge, and you don't want to buy a replacement, then there is not much can do other than to keep using your laptop with the charger. All batteries have a time life span.

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Take out the AC power jack and then remove the laptop battery. Plug AC power back in and see if the laptop will turn on. If it turns on let it boot the operating system and then shut down as normal, remove the power cord and reinsert the battery and again see if it will switch on. If it does then there has been a glitch with the battery. If it doesn't then there is a problem with the battery.

If the laptop won't switch on either with or without the battery then there is a possibility that the motherboard has developed a problem.

Good luck.

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If the power supply does not run the laptop without the battery, then the problem is the jack in the laptop, over time the plug breaks free of the motherboard causing intermittent operation or no power. If the power supply runs the laptop without the battery, it is the charging circuits on the motherboard that is the issue.

Jan 04, 2011 | Computers & Internet

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My dell latitude c640 keeps cutting off. i didn't receive any instructions when i purchased it off Ebay. What do you think the problem maybe?

If it is plugged in when it cuts off. I would say the mainboard is bad. If it does it when on battery power. Its probably just running out of battery.

Aug 14, 2009 | Dell Latitude C640 Notebook

1 Answer

New battery and still won't charge.

first, check that the battery connection isn't blocked by a sticker or something.
second: try disconnecting the battery and ac and hold the power button for 1 minute. then give the battery and ac another try.

let us know how it goes.

if it still doesn't work, time for a warranty replacement.

Jun 30, 2009 | Dell Latitude C640 Notebook

1 Answer

Battery won't charge. Will run on A/C power fine.. what could be the issue??

Could only be one of two problems, battery is bad (most likely) or the board that powers the battery is bad (often its the main system board.)

Jun 08, 2009 | Dell Latitude C640 Notebook

1 Answer

Dell latitude C640 laptop battery will not charge. Got a new?? battery but it won't charge either. I am able to run on A/C power just fine.. When I got the computer (used) the battery worked fine... what...

Try taking out battery and plug in power. If it works, battery is faulty. If not,
Try taking out your hard disk plug in power, if it works, hard disk is faulty. If not,
Try taking out memory card, if there's a sound, memory card faulty. If no sound, it's your motherboard that is causing the error.

Note: If machine is under warranty no need to pay for the repairs.

Jun 08, 2009 | Dell Latitude C640 Notebook

1 Answer

No power

check your power supply and make sure the proper power at the ends and the light is on the power supply, I no those C640 s have a problem with the darn plug in and the pins in the laptop may have got bend or broken check that out and if all the pins are not bent. your power supply may be bad check that out, if so you can go to and order one for fairly cheap. I think that will fix your problem.

Dec 21, 2007 | Dell Latitude C640 Notebook

1 Answer

Dell c640 battery problem

This sounds like it is not getting enough amperage from the power brick- check which model power brick you have. I'm not 100% sure but the pa-6 family may not provide enough power to charge and run the laptop at the same time. the PA-9 should- if it's rated at 4.51 @20v - that works out to about 90watt. If you DO have a 90 watt power adapter and it's still giving the orange then red flashes- and will not charge when the laptop is off- you probably have either a bad battery, or the motherboard is faulty and has a bad charge circuit, or a loose power jack. What does pressing the little button next to the charge indicator on the battery do? Flashing every other led- 1,3,5 is BAD, so is 1 and 5. You also might have a 3rd party refurb- that had the guts torn out and is not properly "seen" by the laptop.

Dec 16, 2007 | Dell Latitude C640 Notebook

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