today suddenly my left arrow key stops working, i have tried cleaning the key but nothing worked, it is very unresponsive works once out of 50 but accidentally i found that when i press my left arrow key with my Fn key its works this is very strange and there is one thing common among both the keys that both are on the 3rd place from their respective corners may be there is some malfunctioning happened in the circuit, My laptop is HP Pavilion dv6t 3000 cto with backlit keyboard and i am using windows 8 however i have check the key on bios also. so please tell me a solution to fix this.
Sometimes the keyboard controller misses a the release of a control key due to timing issue /bugs. When this happens the controller thinks you are still holding down a key.
Now when you actually press the key the controller thinks you just released it. If you press another key, the controller thinks you are holding down a key and pressing the second key. (this is how you send control codes, like shift, cap lock, alt, crtl,...)
-you can sometimes hit both control keys on your keyboard and reset the controller
-you might have to power cycle the keyboard to have it start up again in the correct state
- you might have to get a update patch from your vender
- try running cmd.exe and type something to see if some strange characters come from the keyboard. Often they will look like you get two characters for each one you type ( maybe ^ in before a character)
Replacement keyboards for most laptops can be bought off eBay for $15-$20.
The keyboard is usually the easiest "not user serviceable" part to replace. You remove some or all the screws from the bottom of the laptop, lift up the keyboard, detach one or two ribbon cables, then install the new keyboard. There may be a little more disassembly if your laptop integrates the keyboard and touchpad into one unit. Google for keyboard replacement instructions specific to your particular model, then decide if this is something you think you could handle. (In particular, removing the ribbon cable requires flipping a latch on the connector to release the ribbon.)
As for what's causing your problem, most keyboards don't actually have a separate signal for each key. The keys are broken up into grids of rows and columns, with each row or column generating a signal. It's possible when you're holding down the fn key, a little extra voltage is being sent to your left-arrow key which is allowing it to work. (This is the reason gaming keyboards can be more expensive. They use smaller grids or no grids, to allow you to simultaneously depress more keys without generating false keystrokes.)
You can try to diagnose the problem or try simple fixes like cleaning it or blowing it with compressed air. But for $20, you're probably better off not wasting time and just replacing the keyboard.