180w laptop charger replace 7.4 plug connector

i dont trying to use non dell adapter i only want replace 7.4 mm plug i upload photos for more info

You could very likely have problems in any case since you are trying to use a non-Dell adapter. In those cases the adapter is usually not detected as a genuine Dell adapter and the results are the battery not charging. And trying to modify an adapter by cutting and splicing is also not a great or safe idea.

In addition the problem you are seeing is due to the Dell adapter having the extra wire to confirm to the Dell laptop that it is in fact a Dell adapter.

Sorry for the confusion as I assumed you were trying to use the non-Dell adapter. But the problem still is that the Dell adapter plug needs that extra wire to communicate to the laptop and confirm that it is a genuine Dell adapter. My guess is that you cannot use the plug from the HP adapter for that reason.

sad reallity but why?  

+ - and why its need third wire? :@ :@ 

@ejn63 is spot on ( I forgot about the IC chip..thanks @ejn63 ). And just to add those genuine Dell adapters are available here at Parts-People.

Further, no matter how you connect the wire, only an OEM Dell adapter will have the IC (chip) inside, which is what is needed to identify the adapter to the system.

Instead of trying to jerry-rig a solution, simply purchase an OEM Dell adapter.  One mis-step with what you're trying  to do and you'll turn the need for a $30 adapter into the need for a mainboard that could be 10-20 times that cost.

i have that oem adaptrer you can check it on pictures i just want plug 

What to do how to wire now them ? i get new plug 7.4mm with 3 wires

Red - inside

White - Outside

Black - Center