First of all check out the AC adapter (Charger) and see if it is putting out 18.5 Volts DC
If you do not have a multimeter, an economical one can be purchased for around $8 to $12.
Carried in a multitude of stores. An auto parts store is one example.
Analog or digital, either one will do. (I prefer analog with a meter, and a needle)
Plug the AC adapter into power. (Not plugged into the laptop)
In the plug at the end of the cable from the AC adapter, that plugs into the laptop, is a Center hole, and a metal shell which surrounds the outside.
The center hole is Positive. This is where the Positive (Red) probe lead touches.
The outer metal shell is Negative. This is where the Negative (Black) probe lead touches.
Function knob on multimeter is set to DC Voltage.
(Symbol is a dotted line over a straight line.
The curved line over a dotted line is for AC Voltage. VAC, and VDC are also used. Voltage AC, and Voltage DC)
Voltage reads close to 18.5 Volts? (DC)
Have a helper wiggle the cords around. The AC cord that is connected to the AC adapter, and the DC cord that comes from the adapter, and plugs into the laptop.
See if there is an intermittent reading.
Indicates a break in the wires of the cable.
If there is a break most of the time it will be where the cable meets a connector, or cable meets the AC adapter, or meets the AC plug that plugs into the receptacle. (AC receptacle. Surge protector, or on the wall)
AC adapter checks out OK?
Go to the DC Power Jack.
AC adapter removed from laptop, Battery removed also.
The DC Power Jack is the round port on the laptop, that the plug from the AC adapter plugs into.
See if the center pin is loose. Try to gently wiggle it. You may have to use a tool such as a pencil.
Center pin checks out?
See if the metal shell that surrounds the center pin is loose.
Either one indicates replacing the DC Power Jack.
The DC Power Jack for this model is not soldered directly to the motherboard. The rectangular DC Power Jack slides down into a slot in the outside of the laptop's lower case.
The DC Power Jack has a cable coming from it, and the connector at the end of the cable plugs into the motherboard,http://www.machinaelectronics.com/store/buypart/HP_Pavilion_DV8000_DV8309US/DC020005G00
Click on the photo to enlarge.
No damage apparent from outside the laptop?
Suggest you remove the DC Power jack and cable, and perform a Continuity check on it.
(Function knob set to Ohms. 1K
Should have an Omega symbol for Ohms. Look like an upside down capital U.
Positive probe lead touches the center pin. Negative probe lead goes into one of the three socket holes, at the opposite end of the cable, in the connector. (That plugs into the motherboard)
You can't physically see what wire goes to what unless you remove the sheath off of the cable.
No need. Just touch all three socket holes one at a time.
If there is no reading you have a break in the wire in the cable, or the wire's connection at the DC Power Jack is bad.
Once you find out what wire (Socket hole) is for the Center Pin, run a continuity check on the Outside Shell of the DC Power Jack.
Now connect the Positive probe lead to the Center Pin, and the Negative probe lead to the socket hole for the Outside Shell. There should be no reading.
If so wires are touching inside the cable.
DC Power Jack and it's cable check out OK?
Suspect a bad sensor on the motherboard. A Chipset.
Reads when the AC adapter is plugged in, and reads when it alone is being used.
Reads if the Battery needs a trickle charge, or a full charge, or no charge.
Requires motherboard replacement.
NOT advertising for either seller above. From a quick search. Proceed at your own risk.
HP Support > Pavilion dv8309us Notebook PC > Manuals,http://h10025.www1.hp.com/ewfrf/wc/manualCategory?cc=us&dlc=en&lang=en&lc=en&product=3192906&
In the list left-click on -
HP Pavilion dv8200 Notebook PC, HP Pavilion dv8000 Notebook PC - Maintenance and Service Guide.
This is a free Service Manual.
This is a PDF file. The computer you are using now has Adobe Reader on it, which uses PDF files.
After you click on the above link it may take up to 30 seconds for the first page to come up.
It may also take additional time for the file to fully download.
You can save a copy to your computer. (The above is a temporary download. After you close the PDF window, you have to go back to the link, and download again)
If you save a copy to your computer you can burn it off to CD disk, and have it anytime you want.
After checking out that the copy is good, you can delete it from your computer, and save harddrive space.
In the Bookmarks menu to the left, left-click on the + sign next to -
Removal and replacement procedures
Scroll the page down, and left-click right on -
5.23 Fan Assembly (Page 162)
Page 165 deals with the DC Power Jack and cable removal. (HP - Power Connector Cable)
5.16 System Board deals with replacing the motherboard. (Page 140)
For additional questions please post in a Comment.