Lowering the power of a 55W HID ballast

Many biker found their 55W HID Xenon installtion is pretty attractive because of its brightness. But after a year or so, the overdriven HID will release enough heat and UV that scotched the reflector chrome. One may even appreciate the burnt smell because of the high temperature.

So this is how a overdriven 55W balast be tamed to a lowered power ballast. The job takes 10 minutes to complete. In this mini ballast, I took away the waterproof coating. With some luck, I found the very tiny variable resistor. 

The stock ballast took 4Amp at 13.5V at a power rating of 55W. By turning the resisitor clockwise for 1/4 turn, the current can be reduced to 3A , i.e. 40W. This makes the lamp much cooler. 

Mitsuba FR33-025 flasher relay LED mod

Finally  succeed to hack this relay.
The circuit has 2 protection circuit for the controller IC MC33193:
1) pin 7 sense the shunt and see if abnormal current detected for blown bulb
2) pin 8 sense the ground connection through the bulb and the signal switch, then start the flash sequence. From the datasheet , it should ground through the bulb and a 3.3k Ohm to pull low, the starter than fires the relay and connect the +12 which pull pin 8 low again.

Therefore, cutting pin 7 alone will not fire the 4 LED successfully as pin 8 cannot  sense the ground through the LED (high internal resistance) on closing of the turn signal switch (normally through the 6 Ohm bulb ~6 Ohm).

Therefore, the trick is to put a 1/4W resistor across the ground and the signal pin of the relay to trick the controller IC.

Summary
1) cut Pin 7 to bypass the fault detection
2) solder a 2.2 K Ohm resistor across the ground pin and the Light pin

Test after mod : no leaking current on switching off , very efficient LED ~ 300mA @ ~4W, which is much brighter than stock 25W bulb.

All 4 LED can flash with normal frequency. 

The main disadvantage of this mod is that the relay is put into always on mode, which may shorten the life of the mechanical relay inside.

I end up by  putting two 0.25W 1k Ohm resistor to the two rear turn signal wire to fool the FR33 relay. It works perfectly and now all 4 LED works.