left headlight dim wiring upgrade?

Hi all. What i though was a blown globe on my left side headlight and changed to h4 lights instead of the sealed light, It turns out that the light still is dim hi and low. I hooked to the drivers side and works ok so some wiring is stuffed somewhere, What i want to to is put a 2 relays behind the left side light as the right side wiring runs past there and hook them to a relay. My only problem is the system i think is a negative system, Below is the link to the FSM wiring, If someone could tell me how to hook up the system to the relays i would appreciate it. It is also a good way to go so i can upgrade the wiring to bigger than the thin wires they supply.

Link to Toyota 4runner 1991 headlight wiring diagram.

Thanks
Stuee

Sorry no one has had any help for you.  I just looked at your question, do you still need help with it?

Hi, yes still have the dim light. If you could help i would appreciate it. thanks

As you stated earlier, the system does depend on ground to switch between high and low. If you wire the relay, it will not help you until you find the bad part of the power supply to the bulb. The bulb switching from hi to low, but just being dim on both, tells me that there is a bad connection on the power source to the bulb.

You need to check voltage to the fuses. Your headlights need to be turned on to check this. Ground the black meter lead to the negative terminal of the battery. Now touch the red lead to one end of one of the fuses. Notice the voltage on the meter. Then check the other end of the same fuse. Then do the same on the other fuse. If there is 12 volts on all 4 of the connections you just checked, check for 12 volts on the 3 wires of the headlight plug. Compare those results to the other headlamp and let me know what you find.