1947-87
Pull Up Resistor. Classic Instruments tachometer and an LS engine
Part Number: 4-20957
Pull Up Resistor Classic Instruments tachometer and an LS engine. 1947-87 Chevrolet / GMC Truck
- If you have a Classic Instruments tachometer and an LS engine, you will need to boost the power of the tachometer signal from the ECU in order for it to work. This is because the tachometer signal from the ECU is a 5V square wave and some Classic Instruments tachometers are designed to work on 8V and higher square wave signals. To get the 5V ECU signal to work, a special pull-up resistor that installs between the +12V gauge power and the signal terminal in order to boost the signal strength to work with the tachometer.
