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Replacing a potentiometer with something to lock in 1 value

H

hotrod

Jan 1, 1970
0
Hello, I am trying to clean up the engine bay of my Mustang. It is
drag car and I no longer need emissions equipment.

I want to remove what is called the EGR system. Exhaust Ga
Recirculation

This consists of a solenoid which controls vacuum to a EVP Exhaus
Valve Position Sensor

It is a potentiometer I believe. It is a plunger that moves in and ou
when vacuum is applied/removed. I have completely removed the vacuu
to it and it always read closed, giving me a check engine light. Yo
can trick it by wiring a gizmo to the connector to make the EEC (ca
computer) always things it is open and getting a signal

There are 3 wires
1)VREF (voltage referecne from computer) This is 5.0volt
2)Signal Return (ground to computer
3)Signal Voltage to computer

As vacuum is applied to the vavle, the plunger moves and sends a lowe
voltage (from 5.0volts) to the computer

The test for the sensor is 5500 ohms fully closed, to 100 ohms full
open

I do not know how to wire the 3 wires or what to use for parts to mak
a permanent, say 2500 ohms signal to the computer. I understand tha
the sensor is supplied 5.0 volts and the potentiometer (?). Whe
there is no vacuum present, the computer sees very little voltage
and as vacuum is applied, the plunger moves and drops resistance
allowing more voltage to be read by the computer

I know there is a simple way to wire up the sensor to put it at
constant 2500 ohms or so, but I do not know what to use. Would I us
a transistor, multiple resistors

I can fool the computer by locking down the plunger to read hal
closed, but I want to removed the sensor altogether and replace i
with a simple resistor type settup that I can connect directly to th
wires inside the car near the computer

Thanks for any help. I do know some electronics, but it is limited t
fairly simple circuits. I'm not really a beginner, but don't have an
formal training or schooling

Pau
 
D

DesignGuy

Jan 1, 1970
0
hotrod said:
Hello, I am trying to clean up the engine bay of my Mustang. It is a
drag car and I no longer need emissions equipment.

I want to remove what is called the EGR system. Exhaust Gas
Recirculation.

This consists of a solenoid which controls vacuum to a EVP Exhaust
Valve Position Sensor.

It is a potentiometer I believe. It is a plunger that moves in and out
when vacuum is applied/removed. I have completely removed the vacuum
to it and it always read closed, giving me a check engine light. You
can trick it by wiring a gizmo to the connector to make the EEC (car
computer) always things it is open and getting a signal.

There are 3 wires.
1)VREF (voltage referecne from computer) This is 5.0volts
2)Signal Return (ground to computer)
3)Signal Voltage to computer.

As vacuum is applied to the vavle, the plunger moves and sends a lower
voltage (from 5.0volts) to the computer.

The test for the sensor is 5500 ohms fully closed, to 100 ohms fully
open.

I do not know how to wire the 3 wires or what to use for parts to make
a permanent, say 2500 ohms signal to the computer. I understand that
the sensor is supplied 5.0 volts and the potentiometer (?). When
there is no vacuum present, the computer sees very little voltage,
and as vacuum is applied, the plunger moves and drops resistance,
allowing more voltage to be read by the computer.

I know there is a simple way to wire up the sensor to put it at a
constant 2500 ohms or so, but I do not know what to use. Would I use
a transistor, multiple resistors?

I can fool the computer by locking down the plunger to read half
closed, but I want to removed the sensor altogether and replace it
with a simple resistor type settup that I can connect directly to the
wires inside the car near the computer.

Thanks for any help. I do know some electronics, but it is limited to
fairly simple circuits. I'm not really a beginner, but don't have any
formal training or schooling.


The potentiometer is a resistor (two outside connections) with a sliding tap
(middle connection). As the pot is turned the resistance between one end and
the tap increases, while the resistance between the opposite and and the tap
decreases.

What you need to do is set the pot where you need it to be, and then remove
the wires (carefully noting their original locations). The using a
multimeter measure the resistance between one end and the center tap, and
then the other end and the center tap. Those are the values of the two
resistors (R1 and R2) that you will need.

The circuit will look like this:

|^^^R1^^^|^^^R2^^^|


The vertical lines indicate where the wires will connect. One end of each of
the two resistors will be connected to each other.
 
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