Voltage to ac compressor is 4 volt

you may still need more freon ---a line/seal has failed --moisture in lines etc https://www.autozone.com/diy/climate-control/diagnosing-car-ac-problems https://cartreatments.com/car-ac-not-blowing-cold-air/

Good idea to bench test, whatever it is.
Low volts? What is the high volts?
Belt driven or electric compressor, what you choose to start up needs to make, break, and carry the load in amperes. Thermostat, relays, contactors, solenoids, inverter, transformers, coolant sensors.
It's sometimes chosen, more practical, to use a control circuit (low voltage), and a power circuit(high voltage), for controls and for power hungry consumer loads.

Should be 12 volts. Check the AC relay in the fuse box. Often you can change it with the horn relay to test the relay.

diodes do not regulate charge
simply put diodes are one way valves for electricity and are used to rectify alternating current (AC) to direct current(DC)
you use a voltage regulator after a rectifier pack to control the voltage from an alternator of maintain a max voltage of 14.5 volts dc
take it to an accredited bike electrician

YOU COULD HAVE OPEN OR SHORT IN THE BLACK YELLOW WIRE GOING TO AC COMPRESSOR CYCLING PRESSURE SWITCH. CHECK FOR A SHORT OR OPEN IN RED YELLOW WIRES AT THE AC PRESSURE CUTOFF SWITCH. USE VOLT METER AND CHECK FOR VOLTAGE AT BOTH SWITCHES. PROBLEM COULD BE IN THE EATC MODULE THAT SEND POWER TO PURPLE WIRE THAT FEEDS THE AC PRESSURE CUTOFF SWITCH AND AC CLUTCH CYCLING PRESSURE SWITCH THEN FEEDS THE AC COMPRESSOR CLUTCH SOLENOID.

Check control panel switch. Should be sending voltage to relays.

When the ac acts up,test voltage at the ac clutch,if there is voltage(12 volts to 14)then the clutch is the problem,also,try and wiggle the low pressure switch ,to see if it tries to come back on,,,have some one put some ac gauges on the ac system and let the ac run,and watch to see if the low side falls down to 25 psi or lower,if it does,then the orifice tube is stopping up.If this was at all helpful,please rate,thank you.

you will need to replace the compressor cycling switch, this part is screwed into a bung in the low side AC line under the hood.

faulty compressor

almost like a single faze situation u need to follow wires check were u r loosing ur voltage,switch,fuse ext