Generally the only issue with converting warning lights to LED's is with the engine charge lamp, on earlier cars with such. The alternator requires an initial field current to kickstart it's output and an indicator bulb of a specific wattage (hence resistance) typically 3 watts, provides this. The much higher effective resistance of an LED would not allow sufficient current so a resistor in shunt across the LED is required to simulate, 48 ohm 3 watt works.
