Im tryin to replace the tape deck in my ford ka

Here's the link and I'm sure you will get the solution of your problem
Ford Laser sedan 1998 Wiring Diagram Repair Service Manual

Did the xplod deck work correctly before you installed it? When it cuts out does it loose all its memory and setting and go back to factory defaults? It is possible that the deck is faulty.

Battery Cables maybe? Check the Cable ground to battery make sure it is grounded to Battery and Frame also check Starter wires and the Positive to the Battery.

sounds like you grounded out the speakers

do it the old fasion way i have never used diagrams for splicing iht existing wiring.
simply a test light to find constant+ switched + ground, and such thin trial and error for speakers! there's 3 screws above the heater/vent controls, and two screws behind the ashtray - you've gotta pull it all the way out. then the centre console comes out, along with the stereo. the heater control knobs pull off by hand, no screws, you may also have to remove the choke 'knob' to get the plastic consol off. The knob is held on by a screw on its underside, then you will have to unscrew the collet (chrome thing) with a screwdriver, you will see what I mean.

For speakers, if the car already has them then sweet, but if you need to check polarity is correct get a AA battery put the wires on either end, and if the speaker moves 'out' polarity is correct as per the signs on the battery,if the speaker moves in the polarity is wrong. does it have the standard pioneer deck in there?
if so and u want to go by those colours

red = acc
orange = +12v
black = ground

green = left +
black = left -
grey =right +
black = right -

(cut the joining black wires on the plug (the one that has 2 black wires coming out is the front, the one that just has one black then a bridge across the plug is the rear)

if u want to go behind the plugs then
blue/red = left +
blue/yellow = left -
blue = right +
blue/white = right -
(same for rear but on a seperate plug)

dont remember the colours for acc and 12v (they're blue with some trace, one of them is black i think)

ground is black (might have grey dots)
illumination is red/black

could the wire be on the run side of the ignition, meaning you have to start the car. or check that your ground lead is truly a ground.

Clean the battery connections for good contact and that the battery is well charged (should read 12.6 volts without the engine running).

try the locu libbary they should have book on it

I believe you have a wire touching a ground somewhere in your car stereo circuit. Most likely there is a speaker wire in your dash that is the cause. Here is a reference: http://www.bcae1.com/brighead.htm
Also make sure the RCA's are taped up in your dash, they will create an entrance to feedback from the amp, which will inturn make your subs go crazy. Also, unplug each channel RCA from your amp and see if it stops, you may have a break in your RCA's causing a ground.

please check the VDR in primary supply side.its directly connect to bouth N&Live wire connections of supply.
nuwan.