Page created by T Sunday July 15th 2012:
HR Fuel Gauge Repair:
66hrute successfully repaired the Fuel Gauge in an HR by replacing the burned out 12 ohm 5% resistor inside it.
HZ Fuel Gauge:
THe HZ Holden Fuel Gauge is powered by a Thermal Voltage Regulator.
Thermal Voltage Regulator:
The ex-factory Voltage Regulator is a thermal device meaning that it is operated by temperature. When the device is cold its 2 contacts are closed, providing current to the Gauges. The device is heated by a winding of wire. When the wire reaches temperature the contacts open, preventing current from reaching both the Fuel and Temp Gauges. This action keeps the Gauges from over or under-reading.The thermal Gauges are so slow to operate that the on off action of the Thermal Boltage Regulator is not shown on the Gauges.
Solid State Regulator:
All Holdens after HZ used a Solid State Regulator, such as the 7805 Integrated Circuit. It is advisable to convert to the Solid State Regulator for improved reliability if any work is being done on the Gauges. The Solid State Regulator has internal thermal and overload protection making it ideal for use in OH dash boards.
The Fuel And Temperature Gauges Stop Working:
If this happens the cause is highly likely to be a failure of the Voltage Regulator. Steps for converting to a Solid State Regulator are below.
Steps For Converting To A Solid State Regulator:
1. Disable the Thermal Voltage Regulator by bending the contact up and cutting its wire (Pic 4).
2. Install the 7805 as shown (Pic 5, Pic 6, Pic 7 and Pic 8 ). Use 2 amp hookup Wire. The black sheath is called heat shrink and can be shrunk into a tight fit by blowing it with a hairdryer.
It is advisable to fit a heatsink to the 7805 regulator to help it stay cool.