Brown/white wire, blue wire, what are these?

[Custom/Ten]

Hey guys, I'm trying to figure out what these wires are for. They come down from that area at the top rear of the hood and were taped up with the green wire that goes to the temp sensor in the head and the red wire that goes to the carb (rochester monojet). All four of the wires come down and run from the rear passenger side of the valve cover to the front, then wrap around the front and the brown/ white and blue wires were cut off right at the front by the temp sensor in the thermostat housing. From what I've read they could have something to do with a vacuum advance delay for auto trans, which I don't have.( mine is three on the tree) Or a resistance wire for the alternator but my alternator works fine. I'm hoping one of the hooks up to the temp sensor at the thermostat housing to make the idiot light work because the only things that still don't work on this truck are the temp idiot light and the new temp sensor which won't go past 100 degrees but the temp gauge may be a discussion for another thread. I just need to know what the brown wire with the white stripe and the blue wire are for. I'm gonna try to figure out how to post some pics, I'm not really sure how, this is my first thread. I just joined today, thanks guys this forum is awesome!

[Custom/Ten]

Also should prolly say that this is a 1972 custom/10 with a 250 inline 6. No AC

[Custom/Ten]

[Custom/Ten]

[Sklptrljay]

If memory serves those wires are for the voltage regulator. Which you may not have any more if you have a newer style alternator. Go to the electrical page and you will find a wiring diagram.

[Sklptrljay]

Just saw the picture. The green is your horn. Use the diagram and trace the wires back to see if they go back to the harness and haven't been spliced with a different color.

[Sklptrljay]

Actually the temp is a green wire too. It looks like the horn though because of the connector and wire gauge.

[Custom/Ten]

Ok thanks jay, I will try to find a wiring diagram. Then maybe the idiot light above my head will turn off haha. Not sure if I have a newer alternator or not. Only had the truck a couple months still trying to figure out what all i got. Ill post a pic of the alt, maybe someone will know which it is.

[Custom/Ten]

[Custom/Ten]

Well can't find any diagrams for the 250 and can't find the electrical page. I will get off the iPod and try with a computer but if anyone is positive what these wires are please let me know, thanks. I do have a manual for 67 to 87 gm trucks that I got at the auto parts store, but I can't make any since of it.

[Custom/Ten]

Just followed the wiring to this relay next to the back of the fuse box what is this, is it TCS ( transmission controlled spark), I thought those were only for automatic transmissions, not my 3 on the tree. The black wire goes down to the transmission.

[Custom/Ten]

Brown wire with white stripe makes a stop at this connection where it splits and sends another brown/white into the fuse box.

[Avitech]

brown/white wire is the alternator side of the circuit for the battery gauge in the instrument panel. The other half is a black and brown wire, (mine is all black incidentally,) to the battery that has a similar fuse to the brown/white wire. the green wire should be the temp sensor if it was routed through the wire gutter at the back of the hood. the blue wire would be for an oil pressure sensor on the v-8 models. maybe your truck had a similar experience to mine and had a swap to the straight six from a v-8 in it's life.

[Custom/Ten]

Green wire Is for sure a temp sensor wire, but I think that relay may be for a TCS, anybody else have one there, I think maybe somebody removed the TCS and left the wires for it. Would that explain why I have a two temp sensors or do they always have one in the t-stat housing and head like mine? small green wire with white stripe on left was cut off and just hanging there, not sure what that was for yet. Bigger green on right is temp.

[71K20chevy]

The green/white stripe wire looks like it plugs into the sending unit right by it, but don't hold me to it.

[Custom/Ten]

I'd agree with you chevy but plugging that wire in wouldn't do any good because its ten inchs long, the other end is cut off lol.

[Custom/Ten]

Just unsubscribing to some old dead threads and came across this guy. I was so clueless when I first got my truck. I've really learned a lot with everybodys help on here. Just though I'd settle this in case some clueless guy like me comes across this in the future.


The 3 wires in question were parts of my transmission controlled spark which the previous owner had half removed. I removed them all and have had no issues, just made it look a lot cleaner under the hood. Everything I've read on here says tcs never really worked that well which is why most people just removed them.