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.
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Re: c640 Battery runs laptop - a/c doesn't
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 managementsystem or chip is common with these, and the motherboard will have to be replaced in order to fix it.
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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.
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.
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.
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.
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 Dellsupport.com and order one for fairly cheap. I think that will fix your 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.