I have a friends HP Pavilion DV4000 laptop, it has been dropped but there is no external physical damage, but it has stopped charging in the normal way.
When I was given the laptop it was completely dead, it had in fact run the battery completely flat, a fact that not forthcoming until I had stripped it down looking for any signs of obvious damage or broken connections etc. which I didn’t find.
I purchased another DV4000 off Ebay with a damaged screen, having used the hardrive from the original and connected to an external monitor everything worked fine including the charging, the battery now back to 100%.
The original laptop screen was reattached and all was fine picture perfect everything running as it should, almost.
The problem I have is that the AC adapter will only charge and run the laptop when an external monitor is connected to the VGA socket, disconnect and it reverts back to battery only, considering the screen and inverter are the only components used from the original I assumed that there may be a problem with the inverter, I found another screen assembly and replaced that, and the problem is still there.
I now have Two DV4000 laptop’s which I assume have the same fault, the hardrive & AC adapter are the only two components that are shared, both work very well apart from the need to connect them to an external monitor through the VGA socket in order to get them to run and charge the battery.
HP help desk suggested downloading the latest Bios F17 which I but didn’t resolve the problem, it has been suggested that the power socket could need repairing, but it doesn’t affected either unit by moving the AC plug at all.
In a nut shell plug an external monitor into the VGA socket and the AC power and charging is as it should be, the monitor doesn’t need to be powered either.
As an enthusiastic amateur and some what out of my depth, I feel its time to get some of you experts onboard, any suggestions welcome if kept clean.
A thankyou to Colin from www.truestate.com/hprepair/ for his useful and friendly help
Many thanks, Bob

update.
It appears after that connecting the monitor via the VGA socket is providing an Earth enabling charging to operate, the AC adapter socket has been tested OK.
It has been suggested that a chip on the VGA circuit board may have failed causing the previous strange behavior.