[stubborn72k20]

ok heres my situation. i have the oringinal wiring harness in my 72 chevy truck. but its shot. and i cant afford a new one. and i need taillights and fuel gauge. can someone please tell me or show me how to hook all this up. thank you.

[75gmck25]

On my '75 the tail-light wiring runs from the fuse-box area in the engine compartment, down the driver's side frame rail to the tail-lights. The wiring colors are standard for GM (white, brown, green and yellow), and you can use replacement wiring that is used for trailers. Most auto parts stores carry the color-coded wiring.

The gas tank is grounded - so first make sure the ground wire is still there.
There must also be a sending unit wire power that runs from the sending unit to the dash gauge, and then through the ignition switch to 12 volts. On my truck the sending unit wire is tan, but I don't know about your '72.

Bruce

[stubborn72k20]

so which wire going to my fuel gauge is 12 volts. and what do i need to do to hook my fuel gauge back up. i dont wanna run any of my other gauges. just my one fuel gauge. thank you. because theres a short somewhere...

[75gmck25]

Is there power to the instrument panel, or is something grounded or shorted so you can't use the stock panel? If you can't get the panel to work, it might be easier to add an external fuel gauge.

The instrument panel should have a main ground wire (black), and if its disconnected you will have problems with all kinds of things. You also need 12 volts from the fuse box to the instruments, and there should be a separate fuse for that circuit. Power will be switched on and off through the ignition switch.

Bruce

[stubborn72k20]

i gutted everything. cant i just run 12 volts to the switch or something. im looking to do something simple. thank you

[75gmck25]

Locate the sending unit on the gas tank first. Find the sending unit wire (the other wire will be ground) and trace it back toward the instrument cluster.
Buy an add-on fuel gauge that uses a 0-90 ohm sender (very common) and install it under the dash.
Connect 12 volts switched to one side of the gauge, and the sending unit wire to the other side. The gauge should now work.

Bruce

[fast68]

taillights are dark brown wires, also for parking lamps and for license plate lamp

all same

commonly the rear harnesses are hacked up a bunch and is why things dont work in the rear.

can make a new one from a donor truck or from an extension cord with common 16 guage copper stranded wires in it

fuel guage is hot all the time to the guage when key is in run position

if the guage reads past full with key on then the wire from sending unit to dash is open somewhere

or the sender unit is junk

ground the black wire at the sender unit and it should peg to the far right side and beyond.... on the guage

if so then the hot is fine to the guage and it is bad sender unit, it wire from it to the dash

check connector at back of cluster also,


zero resistance = empty

90 ohms resistance = full