How can I connect a potentiometer to the solenoid?

I have done a bit of research but cannot find anything hard and fast describing what I am trying to do.

I have a solenoid in the steering rack of my racing car. This solenoid is controlled by the ECU and varies the amount of power steering the rack receives using a solenoid. As the car goes faster it gets less power steering. This is unnerving on track and not optimal.

I would like to manually control the voltage input to the solenoid from inside the car. Solenoid input voltage specs below

• Maximum (highest power steering) 5.5V @ 1.1A
• Minimum (least power steering) 2.1V @ 0.4A

The car supplies 14.9V with the engine running.

I figure I can wire in a toggle switch. When off the ECU circuit is connected and the car runs as intended. When switch on the circuit runs through the potentiometer.

• Potentiometer specs are 20 ohm 0.125W @ 350V AC
• 12V switching voltage @ 1.5A

I have drawn up a small schematic but I do not think it is correct. With the specified potentiometer and a 30 ohm resistor before it I can vary the output voltage between 6V and 1.2V which should be sufficient.

Is this correct or am I way off?

• If the solenoid requires up to 1.1A then your resistive divider of 30K and 20K is completely incapable of providing this by a factor of about 2,000. Even omitting the 20K pot, you could only get about 0.5mA at the most via a 30K resistor. If you did build a resistive divider then the upper resistor would need to be around 8 ohms (again ignoring the pot) and be capable of dissipating 10W. It gets a lot worse once you factor in the pot. At one point you do say it's a 30 ohm resistor and 20 ohm pot but rated at 0.125W which is far too low. I suggest you look at a different method. Commented Jan 26, 2023 at 16:16
• Using resistor divider for such current is not suitable. You should explore other possibilities like using an adjustable voltage regulator or a buck converter. Commented Jan 26, 2023 at 17:16
• are you certain that the device is a solenoid? ... from the description, it seems to be a linear motor Commented Jan 26, 2023 at 18:11
• @jsotola Yeah, solenoids are either ON or OFF, which means he'd only need a manual override switch if he that were the case. This is NOT a solenoid! We need a part # on the device he's trying to control. Commented Jan 26, 2023 at 23:39