Anyone know what these 2 wires are?

[JKtx42]

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Any clue what these 2 wires are for? They go through the firewall and previous owner cut them. 1982 GMC Sierra thanks for any help. Ive looked at wiring diagrams for days.

 

[AKguy]

Can’t tell what color they are. Where are they terminated, if at all, on the dash side?

 

[mtbadbob]

I'm trying to decipher what side of the truck they are on? Are they for cruise control??

 

[deerejohn]

is it a manual transmission? it looks like the reverse light wires that would plug into the sensor on top of transmission.

 

[AuroraGirl]

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no idea where it goes or what its doing

 

[JKtx42]

Can’t tell what color they are. Where are they terminated, if at all, on the dash side?

Top picture is front engine bay side, bottom pic from inside the cab, it’s a green and blue wire looks like

 

[JKtx42]

I'm trying to decipher what side of the truck they are on? Are they for cruise control??

Above where these two wires are coming through is the vacuum line and wires going to gas pedal for cruise.

 

[Termite_Delight]

Might be for dual gas tank switch.

 

[AKguy]

On the 1981 blue/grn is used for the backup switch, and a blue and green is used with the others on the tank select switch.

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[Blue Ox]

My question is, does the truck have the original engine and transmission? Wires may be for something that no longer exists.

 

[Joshua Keith]

Mine runs down the driver side frame, across the back of the cab then to the fuel tank switch.

 

[AuroraGirl]

1980, me, has that there. for the tank switch is either yellow or its not the original wire or its green and the flash and dirt is making it look yellow. it also appears that it should have more than one wire on it(?) but no promises on anything there lol.

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The trans backup switch appears yellow and black
making me think its possible it could be the original 4x4 indicator wiring or something else like the warning light for choke, which I forgot how the light normally is supposed to function. this is 1980 tho, 1981 is new around in many ways, and i would have a NP205 and Sm465 originally, now its np208 but beings how much was rigged replaced this and that for all I know the fuel tank switch isnt the oe one either. The switch, to my understanding, should get both fuel tanks sender and the switch flips which one is displayed by changing the ground provided to the gauge, I may be wrong. if so, I would think this wiring wouldnt head out of the fire wall the same direction or at least maybe not where he shows his going? speculations.

 

[AuroraGirl]

I forgot, didnt lockup TH350s exist and then also have a lockup switch that would kick them off near your feet, which then would run, there by your foot, down the same way the backup switch, to go to your trans?

 

[AuroraGirl]

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This is my truck again and youcan see the blue and green paired wire. goes to something. 4x4 light or backup if the switch has 2 prongs or a fuel tank switch if the unit receives 2 wires ??? who knows

 

[Bextreme04]

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This is my truck again and youcan see the blue and green paired wire. goes to something. 4x4 light or backup if the switch has 2 prongs or a fuel tank switch if the unit receives 2 wires ??? who knows

The fuel tank switch harness on the 1980 trucks(not sure on other years) lives in a separate 4 pin connector near where the throttle cable comes through the firewall.