Instrument Cluster Voltage Regulator

The adjustable LM-317 regulator is a better part than the 7805 regulator circuit widely seen on the internet. The 7805 is specified as 5volts out-plus or minus 5%. That means a possible voltage output of 4.75 to 5.25 volts. If you get a 7805 that is on the low side your gauges may read lower than with the old electro-mechanical regulator.

The Charger Source Guide circuit with the short circuit protection diode looks like a good one to try. Its only disadvantage is it uses fixed resistor values to adjust the output voltage, a potentiometer would be a little more convenient. Although the fixed resistors do have the advantage that once set it will stay in proper adjustment and wont change with vibration or someone getting in there with a screwdriver.

Many of these circuits posted on the internet reference Radio Shack part numbers. With Radio Shack going bankrupt and closing so many stores these part numbers aren't going to be so useful. If anyone wants to build one of these regulators and needs help with parts, let me know.