My controller wont pair with my udi u12

The red light means charging!

There should be a green light on the helicopter that goes off when charged, i think!

Nope.

You have a bad flight control board. There may be a loose wire near 5be charge port making fontact wi5h the output circuit for the main rotors. Good luck

The batteries are just bad. It happens often. If you can find similar rechargeable batteries then try to replace. It might require desoldering and resoldering them in but if you can't return this then that's about your only option (if you are going to fix this yourself).

You mention the controller, new batteries are good for the controller, but you need to have your heli batteries to be charging correctly. If you get new heli batteries, then Check your charger, it is probably not putting out the right voltage.
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Do the lights on the heli come on?

Normal start-up would be:
Turn helicopter on. Flashing light in nose should come on, as well as another blinking light (sometimes towards the rear, sometimes in the "cockpit" area) the helicopter MUST then be placed on a level stable surface until the 'other' light stops blinking, usually a couple/few seconds. This is the gyroscopes synching up and determining the "level" head orientation they will be maintaining. Then power the controller on. Making sure you're not covering the front of the controller with your hands, (the IR signals come out the front like a TV remote) push the throttle control (left joystick) up until the blades move. This what the horribly translated instructions mean by setting the helicopter and controller together.
Don't charge with the controller. It kills your controller's batteries, (which will last nearly forever if you don't use them as your heli's charger) and seems to make the birds act weird. Use the USB charger and a fully powered USB port (back of your desktop, not the front) and go by the light on the charger not an arbitrary time. Plug in charger NOT connected to heli. Look at the light. That is what the light will look like when unit is fully charged. Make sure heli is off. Plug into charger. Charge until light is fully on. If you unplug heli and the light gets brighter, it's not charged fully. A weak USB port (on a laptop or the front side data port on most desktops) may take several hours to achieve full charge. Always cool 10 mins after charging AND 10 mins after flying. Never drain fully, it will kill the Li/Po battery. Land and power off as soon as you can't maintain altitude.
If it is really charged, and you turn it on and nothing happens... no lights nothing. Then it's defective/toast. Return for refund.
These SYMA helis are awesome, and HANDS DOWN the best on the market... but they can be picky/tricky on how they are treated.

Please let me know if this helps.
PvT

If using usb charger use usb port on back of desktop, not data port in front, also most laptops do not have fully powered usb ports due to battery consumption. The wall charger, or a usb charger plugged into a usb/ac adapter (like included with ipods and kindles or sold seperately) is your best bet for reliable charge.
Charging unit should have a light on it.
When charger is plugged into power source and not helicopter, the light will show you {#1} what it looks like when battery is fully charged. Typically this is steady on, and usually red. (sometimes green) When you connect helicopter to charger, the light will change (usually goes dark) to signify it is charging {#2}. When light comes on fully (or completely returns to #1) then charging is done. (Note: charging using a laptop usb or a front side data port usb can take several hours.) Watch the light on charging unit when you unplug helicopter, if it gets brighter, helicopter is not charged, plug it back in. Make sure to let battery cool for 10 minutes after every charge and 10 minutes after every flight, and never run battery all the way down. As soon as you can't maintain altitude, land and power off. Fully draining a Li/Po battery weakens it's ability to hold a charge and can ruin it.
If all else fails, replacement batteries are available from Amazon and many others, they are cheap (around 5$) and very easy to install with no soldering and just a small screwdriver.
Hope this helps
r

i am having the same problem!!! did you ever find out what was causing it???

the charger should plug into the model with a small connector coming from the remote