How to not go crazy trying to perform the CAL SENDER procedure
According to some reference material, the resistive sensor on an Evinrude outboard engine that is used for the TRIM position ranges from 10-Ohm (fully up position) to 88-Ohms (fully down position). I wanted to create a variable resistor for bench testing that would produce this same range of resistance. Using a 100-Ohm linear-taper potentiometer and some standard value resistors, I was able to make a sender with a resistance range of 10.6-Ohm to 83-Ohm.
I connected my bench-test TRIM sensor to my bench-test ICON Pro RPM gauge using the marked "ANALOG TRIM P1-7" and to the 12-Volt negative circuit (the 0-Voltage reference). Then I performed the CAL SENDER procedure.
The CAL SENDER procedure is found in the menu path:
Normal operation ---> EDIT MENU ---> DATA SOURCES ---> TRIM ---> CAL SENDER
The procedure prompts to "HOLD MODE >1 SEC WHEN TRIM IS FULL DOWN." This calibrates the DOWN position and informs the operator "SETTING SAVED."
Next the procedure prompts "HOLD MODE >1 SEC WHEN TRIM IS FULL UP." This calibrates the UP position and informs the operator "SETTING SAVED."
The TRIM sender is then calibrated.
This sounds very straightforward, but accomplishing this nearly drove me crazy.
After performing this procedure several times, the result was always the same: the instrument showed the TRIM position was "TRIM 0%" no matter where I set the potentiometer. My first thought was I had performed the calibration procedure backwards, that is, I set the calibration for UP when the potentiometer was in at maximum resistance, and for DOWN when the potentiometer was at minimum resistance. I re-did the calibration procedure several times, with no change in the outcome. I was becoming very frustrated. I had gone to rather elaborate lengths to create a simulated TRIM sender from a few standard parts, and the resistance range of my bench-test trim sender was within the limits of the actual sender. But the ICON Pro RPM gauge would not be calibrated to this faux TRIM sender. What was wrong? I could not see anything unusual about the resistive input, nor anything unusual about the calibration procedure, yet the TRIM readings on the gauge were stuck at "TRIM 0%.
I took a break for an hour, and concentrated on some other task. Then I returned to the bench and tried the calibration procedure again--with the same result: "TRIM 0%" as a constant reading on the instrumentation.
As I was just about to go insane, a thought occurred to me: better check to see exactly what analogue input has been designated as the TRIM input. To check this, the menu path is
Normal operation ---> EDIT MENU ---> DATA SOURCES ---> ANALOG ---> #2 P1-7
This menu option allows the physical wire input to be configured for a particular category of data input. The choices are
- N/C (No Connection)
- BAIT WELL
- OIL LEVEL
- FRESH WATER
- GRAY WATER
- BLACK WATER
I discovered that the P1-7 input had been configured for "N/C", so the instrument was not even looking at this signal for a resistance that was proportional to tank level. No wonder the CAL SENDER function was not working. I changed the P1-7 input DATA SOURCE setting to be "TRIM."
As expected this change solved all the problems. Once again I performed the CAL SENDER procedure, and finally the desired results were obtained.