Nizar said:
Thank you i think its not the time to switch to leds

maybe next time
Oh its actually a fairly simple process, if you are comfortable with a soldering iron. I've used the calculator at
LED Series Resistor Calculator which gives a nice visual if you're uncertain how this works. What you are doing is taking the horizontal portion of the diagram (the LED and resistor), and connecting either end back into the same place that the original light bulb was soldered.
As an example of using the calculator... for vehicle use, you want to enter 14.4V. The LEDs I used have a current of 20mA, and a voltage drop (forward voltage) of 3.6V. In most cases you will only be able to connect a single LED at a time, and 5% resistors are the most common (you can get these at any Radio Shack). Click on the 'Calculate' button, and it will give you a whole chart of info. What you really care about is the "Nearest higher 5% resistor" (don't use the lower value!) which in this case is 560 ohms, and the "Recommended resistor Wattage" which is 1/2 watt.
Now in my case, my LEDs are 18,000mcd, and using the values above for the best output, these were actually way too bright in my dash! The next higher resistor value in 620 ohms, and the output from the LEDs with this value almost perfectly matched my other dash lights. This also dropped the required resistor wattage , allowing me to use 1/4 watt resistors which are much more common, and about half the price of the 1/2 watt versions.
Play around with the calculator, and hopefully this will start to make more sense. Once you get the idea, its actually pretty simple to make adjustments as you go.