1999 Speedster - checking the speed sending unit

[prairieboy]

I was reading through my shop manual and it indicates to check for voltage as you spin the wheel with the + on one wire and the - on the other wire, but it also indicates to test it while it is connected to the boat harness. It is a closed connector with pins - so how does one do this? I tested the voltage between the two wires that was coming from the boat harness and it was 12 volts - so I am kinda confused how the speed sensor works. If there is 12 v coming to the sensor, does one wire go to the speedo or how does spinning the wheel register the voltage change that translates to the needle on the guage to move?

 

[Sportster-2001-951C-Stock]

I often will carefully back-probe those connectors using thin sewing pins and sneak it though between the wire and silicone insulator. The other way is to use the connector pin extraction tool (you probably want to buy one of these anyway) and remove the pins from the sensor side connector shell and insert them not using the shell back into the harness connector.

The voltage should drop from 12V to about 7 volts once connected and will flutter from ~2v to 7v as you spin the wheel.

Inside the speed sensor assembly of my boat, they used an SS41 Hall Effect IC and a 1/2 Watt 5.6 volt Zener diode. Mine didn't have the optional third wire (white/orange?) for the water temperature sensor resistor but the replacement did and I don't have this water temp gauge so left that 3rd wire disconnected.

Now the sensor I bought has gone out again 3 years later so I'm going to install the original sensor I rebuilt. Here's wiring the schematic of the two components inside the sensor, I drew this on the SS41 IC datasheet:

 

[Sportster-2001-951C-Stock]

I often will carefully back-probe those connectors using thin sewing pins and sneak it though between the wire and silicone insulator. The other way is to use the connector pin extraction tool (you probably want to buy one of these anyway) and remove the pins from the sensor side connector shell and insert them not using the shell back into the harness connector.

The voltage should drop from 12V to about 7 volts once connected and will flutter from ~2v to 7v as you spin the wheel.

Inside the speed sensor assembly of my boat, they used an SS41 Hall Effect IC and a 1/2 Watt 5.6 volt Zener diode. Mine didn't have the optional third wire (white/orange?) for the water temperature sensor resistor but the replacement did and I don't have this water temp gauge so left that 3rd wire disconnected.

Now the sensor I bought has gone out again 3 years later so I'm going to install the original sensor I rebuilt. Here's wiring the schematic of the two components inside the sensor, I drew this on the SS41 IC datasheet:

Correction: The voltage should flutter from about 12V to about 7V while the paddle wheel is spinning.