On my phone displays the time and date are blank and blinking and backlight wont come on. When placed on base it doesn't charge, the charge light blinks when on base.

It could be the backlights, or it could be the power to the backlights. The only way is to phone a local repairer and ask what the charge is likely to be? It varies by country and region and cost of parts.

Have you tried charging (which will reset the handset) in the base charger as opposed to a remote charger? Have you tried moving handset #2 around the house in case the problem is related to interference?

October 10th, 2013 at 9:19 amPROBLEM:
After de-registering handset, handset displays [REGISTRATION FAILED; UNAVAILABLE] when trying to register handset.
This worked for my UNIDEN TRU-9480-2
SOLUTION:
1) Remove handset from base
2) Remove power cord from back of base
3) Press and hold the [find hs] button on base as you plug the power supply back in; the charge light should then be blinking.
4) Return handset to base and it should register
GOOD LUCK!! HOPE THIS HELPS!!

I got my display to come on while on the base unit, by making charging contacts connect. When I did this, then battery indicated it was low, then though I had taken it out a working phone. Maybe the fact is one of charging units are not charging correctly if have several. I have a 3 system unit and it is the base that seems to have the problem.

According to the service manual page 6. four flashes is "Backlight Trouble" so if its the light it self or Backlight Inverter Board i cannot tell you.

Service manual can be downloadet here.
http://elektrotanya.com/sony_klv-26s200a_klv-32s200a_klv-40s200a_klv-46s200a_chassis_wax2.pdf/download.html

If the Plantronics CS55 wireless headset shows that it is on, you have to make sure of the following things.

a. the green LED on the base turns on when you turn the call switch on from the headset.
b. the small green LED on the side of the headset is blinking.
c. the telephone headset is lifted from the cradle.
d. if the headset is not charging and the Amber light on the base does not blink when you place wireless headset on it; trying placing the headset more firmly.
e. If the headset is not charging and the Amber light on the base does not blink even after placing the wireless headset firmly on the charging cradle, you may need to change the battery.

Alternately you can try resetting the Plantronics CS55 wireless headset.

Reset Plantronics CS50, CS60 or CS55 Wireless Headset

If you have problems with the sound or connection of your Plantronics CS50, CS60 or CS55 wireless phone headset, you may want to try to hard reset it using the following steps:

Note: Ensure the IntelliStand switch (on the right side of the charging base) is in the - position and NOT the = position.

1. Press both the call control button and the listening volume/mute button for 5 seconds. When the indicator light blinks release both buttons.

2. Press the call control button again. The talk indicator light will again blink to indicate the headset is back to normal.

3. Disconnect the AC charger from the AC charging jack for 5 seconds.

4. Reconnect the AC charger.

Now give the Plantronics headset a try.

Are you in a 'thick' building that may be preventing the phone from getting the date/time set signal? If so, try plugging the phone in as close to a window as possible to eliminate any possible interference.

the steady red light showing when in charger shows that
it is charging. the blinking red light when taken out of
charger or turned on and off means it is not fully charged.
leave it in charger till red light turns green.

Registering Handsets to the Base
Whichever handset you choose to charge in the base is automatically
registered to the base. Any additional handsets must also be registered to
the base before you can use them.
Be sure both handsets are fully charged.
One at a time, place each handset in the base. The charge/in use LED on
the base begins to flash, indicating the base is registering the handset.
Wait for at least five seconds, then pick up the handset and press
[talk/flash]. If the display shows TALK, the handset is registered. If not,
place the handset in the base to try again.
Press [end] and continue with the next handset.
Note:
Once both handsets are registered, it doesn’t matter which
handset is placed in the base or the charger.
When you charge the handsets, Caller
ID summary screen and the name of
the handset appears.

This can be find from uniden website.
http://www.uniden.com/pdf/DXAI4588-2om.pdf