Inspiron 15-3521 Won't turn on

By the way, I'm assuming the LED ( light) on the new adapter is lite up and not blinking? Also, before replacing new battery, you press 'Power On" button for 20 seconds to drain the residual power ?

If you're comfortable opening computer, I'd suggest removing one component at a time such as memory, graphic card if any or the coin cell battery (CMOS) to see if any will get the computer up and running again. 

First, start with memory(ram). I believe there're two memory slots for your computer. If computer still doesn't start then remove one memory and try using the other one to help determine if one or both are faulty. 

Please view the owners manual thoroughly before attempting to remove any hardware inside the computer in the link below:

https://downloads.dell.com/manuals/all-products/esuprt_laptop/esuprt_inspiron_laptop/inspiron-15-3521_owner%27s%20manual_en-us.pdf

Please check out the video below, hopefully it will be of help to you as well.

Dell Inspiron 15 (3521 / 5521) RAM Memory Replacement Video Tutorial

https://youtu.be/ue1DgTQJsgg

He is talking about the blue LED light near the tip of the AC adapter.

If the AC adapter is functioning correctly, the blue LED stays lit when plugged into the laptop.

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Thanks nyc10036

Yes, please unplug AC adapter from the system and then check if the indicator (light) on the adapter is turn off. The LED indicator may be located either on the AC adapter brick or the adapter (DC) plug. If the indicator is turn off then plug the adapter into another  known-good wall outlet. If the indicator on the AC adapter still doesn't turn on then I suspect the adapter is faulty and needs a replacement. Keep in mind, a faulty adapter will not power on system nor will it charged the battery.

Any update Ann1027?