Adjusting the MAP Clamp Voltage on the Comptech ESM
(Electronic Signal Modifier)
Equipment required:
- Single
output adjustable Lab Power Supply (Instek Model GPS-1850D or
equivalent). Specifications:
Adjustment range 0-15V DC at at least 0.5A.
- Digital
Multi-meter (DMM) with probes (Fluke Model 177 or equivalent)
- Small
straight-bladed jeweler’s screwdriver
Adjustment procedure:
- Set
the DMM to read DC volts and an appropriate range to read up to
approximately 15 volts.
- Before
making any wiring connections, turn on Lab Power Supply. Adjust the voltage control of the lab
power supply to 13.8V +/- 0.5V (13.3 to 14.3V) using the meter on the
power supply or the DMM to confirm the voltage setting. The ESM works from 5 volts to 15 volts
input at the power input wires.
- Turn
off Lab Power Supply
- Attach
ESM red wire lead to the positive (red) binding post and the ESM black
wire lead to the negative (black) binding post of the Lab Power Supply.
- Tape
off the ESM green and blue wire leads to prevent them from shorting.
- Turn
on the Lab Power Supply.
- Set
the DMM to read DC volts and an appropriate range to read up to
approximately 5 volts.
- Insert
the DMM red probe into the small 3/32” diameter hole in the top of the ESM
case labeled + (plus) until it just touches the contact pad on the printed
circuit board inside the case.
Repeat this process for the DMM black probe inserting it into the
small 3/32” diameter hole labeled – (minus).
- The
clamp voltage is adjustable from approximately 2.5 to 3.85 volts DC. Gently turn the small screwdriver
potentiometer adjustment visible through the small 1/8” diameter hole in
the end of the ESM opposite the wire inlet side of the ESM plastic case to
adjust the clamp voltage to the desired setting. The factory setting is 2.840 +/- 0.010
volts DC which matches the output voltage produced by most Honda/Acura MAP
sensor when at average altitudes.
Clockwise adjustment increases the voltage. Counter clockwise decreases the
voltage. The potentiometer
adjustment range is 12 turns from the minimum to maximum setting. The potentiometer adjustment has a
ratchet clutch when it reaches the end of the adjustment travel to prevent
damage to the potentiometer.
- When
the desired voltage setting is achieved, remove the DMM probes from the
holes in the ESM case, turn off the Lab Power Supply and detach the red
and black ESM wire leads from the Lab Power Supply binding posts.
- The
ESM is now ready to install in the vehicle.
- The
ESM voltage is also adjustable while it is installed in the vehicle (with
the ignition power turned on) by following steps 7 through 9.