Gauge connections

[78SierraGrandeTX]

When I purchased my truck the previous owner had another gauge cluster in much better condition. When attempting to replace the gauge in the truck ( which none of the gauges worked) the wiring seems to vary.

I have looked into this issue and have not seen any other post on this forum and those alike, regarding this “green plug” on gauge cluster that is in better condition . The gauge cluster that was in the truck only had the main wiring that connects to the cluster body.

Can someone fill me in on where this green connection plug is supposed to connect too? And what it powers, as it seems the wiring in the truck does not have an outlet for it.

You must be registered for see images attach

 

[C10MixMaster]

the green module if the vehicle speed sensor. I believe it was only for the cruise control in those years. you can unscrew it from the back of the speedometer its not needed on a 78.

yes the wiring pinout varies in different years. the temp sensors are also different on some years.

You must be registered for see images attach

You must be registered for see images attach

there are some errors on these cheat sheets for example the oil pressure wire is brown on most or all trucks but it does seem to be mostly accurate.

COOLANT TEMPERATURE GAUGE PARAMETERS
For Truck Years: 1967 - 1973
The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 350 Ω
Middle Line when sender resistance = 76 Ω
Right Line (Hot) when sender resistance = 51 Ω
For Truck Years: 1974 - 1978
The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 350 Ω
Middle Line when sender resistance = 68 Ω
Right Line (Hot) when sender resistance = 46 Ω
For Truck Years: 1979 - 1990
The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 1,365 Ω
Middle Line when sender resistance = 96 Ω
Right Line (Hot) when sender resistance = 55 Ω
OIL PRESSURE GAUGE PARAMETERS
For Truck Years: 1978 - 1990
(Please note: although factory oil pressure sending units are available calibrated to 60 PSI, 80 PSI and 100 PSI gauges - 60 PSI is the most common calibration. To determine which sender you have, the pressure calibration is stamped into the hex nut at the base of the sender adjacent to the mounting threads. Regardless of pressure calibration, all oil pressure senders have the same resistance values, as indicated below).
The Oil Pressure Gauge Needle Should Point to:
Left Line (Low, 0 PSI) when sender resistance = ~0 Ω
Middle Line (30, 40, or 50 PSI) when sender resistance = 30 Ω
Right Line (High, 60, 80, or 100 PSI) when sender resistance = 60 Ω
FUEL LEVEL GAUGE PARAMETERS
For Truck Years: 1967 - 1990
The Fuel Gauge Needle Should Point to:
Left Line (Empty) when sender resistance = ~1 Ω
Middle Line (Half) when sender resistance = 44 Ω
Right Line (Full) when sender resistance = 88 Ω

 

[Turbo4whl]

the green module if the vehicle speed sensor. I believe it was only for the cruise control in those years. you can unscrew it from the back of the speedometer its not needed on a 78.

yes the wiring pinout varies in different years. the temp sensors are also different on some years.

You must be registered for see images attach

You must be registered for see images attach

there are some errors on these cheat sheets for example the oil pressure wire is brown on most or all trucks but it does seem to be mostly accurate.

COOLANT TEMPERATURE GAUGE PARAMETERS
For Truck Years: 1967 - 1973
The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 350 Ω
Middle Line when sender resistance = 76 Ω
Right Line (Hot) when sender resistance = 51 Ω
For Truck Years: 1974 - 1978
The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 350 Ω
Middle Line when sender resistance = 68 Ω
Right Line (Hot) when sender resistance = 46 Ω
For Truck Years: 1979 - 1990
The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 1,365 Ω
Middle Line when sender resistance = 96 Ω
Right Line (Hot) when sender resistance = 55 Ω
OIL PRESSURE GAUGE PARAMETERS
For Truck Years: 1978 - 1990
(Please note: although factory oil pressure sending units are available calibrated to 60 PSI, 80 PSI and 100 PSI gauges - 60 PSI is the most common calibration. To determine which sender you have, the pressure calibration is stamped into the hex nut at the base of the sender adjacent to the mounting threads. Regardless of pressure calibration, all oil pressure senders have the same resistance values, as indicated below).
The Oil Pressure Gauge Needle Should Point to:
Left Line (Low, 0 PSI) when sender resistance = ~0 Ω
Middle Line (30, 40, or 50 PSI) when sender resistance = 30 Ω
Right Line (High, 60, 80, or 100 PSI) when sender resistance = 60 Ω
FUEL LEVEL GAUGE PARAMETERS
For Truck Years: 1967 - 1990
The Fuel Gauge Needle Should Point to:
Left Line (Empty) when sender resistance = ~1 Ω

Middle Line (Half) when sender resistance = 44 Ω
Right Line (Full) when sender resistance = 88 Ω

Thanks! This will save me some time in the future as I move clusters from one year to another.

 

[78SierraGrandeTX]

That’s a great help thanks! And okay I’ll be taking that off, I have no desire for cruise control as of now