laptop plugged but wont charge

I have a Dell studio 1737 its about 3 years old i have been having some charging issues for a while now i bought a new battery and ac/power adapter from dell i even took it in to a repair shop and was told that the power port was fried and would need to replace it for $260. so i bought the replacement piece opened up my laptop to find the port and chip it is attached to, to look like it was in perfect shape but i replaced it anyway put my laptop back together just to have the same damn problem i never get any kind of error message like cant detect charger or battery, just a prompt that my battery is critically low, now i have both the battery and ac/power adapter in when the battery had a charge it powered on and ran just fine but now that it wont charge if i remove the battery it shows that the ac/power adapter is plugged in but when i reattach the battery it no longer shows that the ac/power adapter is plugged in please can anyone help this is driving me crazy the battery light is blinking red and i have tried many times to remove both battery and ac/power adapter and have had no luck i have even gone into the system stetting and checked for updates for both parts no my power port does not get hot neither does any other part of the laptop