[darren]

I have a 70 GTO the wiring harness is all new front to back and I tried it out and the reverse lights are on all the time when the lights are turned on even when the wires are unpluged from the switch under the dash on the steering colum any ideas where to start

["QUICK-SILVER"]

What brand is the harness you're working with?
It's obvious the back-up lights are now powered by the headlight switch instead of the ignition switch and if color codes are right it shouldn't be a problem to figure out.
Would just like to know if it's something you did or have you purchased a messed up harness.

On do it yourself type harnesses it would be easy to get some wires mixed up and just as easy to figure out.
Expensive finished plug and play harnesses will require a whole different line of thinking.

[darren]

The harness is an M&H purchassed from PY

[johnta1]

Do they blink when the turn signal is on?

[darren]

No they don"t infact the turn signals don"t work so I changed the flashers and checked the fuse and found the fuse burnt out so I changed the fuse and it immediately burnt out again as I pushed it into the panel

["QUICK-SILVER"]

First things first
Double check and verify continuity on all trunk harness black ground wires.
It's very possible that's the whole problem. Especially if everything has a new coat of paint.

["QUICK-SILVER"]

Was typing and missed your last post.
Was that with key on or key off? Turn flasher and fuse should only have power with key on.
Trunk grounds could still be a problem but the fuse blowing may need fixed first.
Start by un-plugging the turn signal column harness connector and see if the fuse blows. If not, ohm testing wires at the column connector should turn something up pretty fast.

[darren]

I unplugged the trunk and column harness and still blows fuse with key on or off so I pulled fuse panel apart and found a pink with double black stripe and got the wiring diagram out and traced it to the water temp sending unit so I unplugged It and no more blown fuses but the signals work and the reverse lits are still on how do you check ground wires for continuity

["QUICK-SILVER"]

Originally Posted by darren

I unplugged the trunk and column harness and still blows fuse with key on or off so I pulled fuse panel apart and found a pink with double black stripe and got the wiring diagram out and traced it to the water temp sending unit so I unplugged It and no more blown fuses but the signals work and the reverse lits are still on how do you check ground wires for continuity

To verify good ground, simply measure resistance from the ground wire to bare metal. You're just making sure paint isn't insulating the ring terminal from making good contact.

It's sounding more like there may be some green wires mixed up in the harness. But lets hope not.

[darren]

Hey Quick-Silver your right the drivers side tail light harness from M&H had the light green and brown wires mixed up I compared it to the orig harness so I switched them around and every thing is working now I have to find a temp sending unit and figure out where the rear blower motor gets its power from and I think everything works thanks for your help

["QUICK-SILVER"]

Has your temperature sending unit got the extra terminals for TCS and or idle stop solenoid control built in? Hopefully it's not more crossed wires but it wouldn't hurt to come up with an ohm test on the old unit before buying a new one.
If it's single teminal green wire only it'll definitely take some more studying.

Good deal on the progress
Let us know how things go

[darren]

Its got 3 prongs on it the engine is a RAIII what would one look for on the ohm test I"ve never had much to do with wiring problems as you can tell but I do have an ohm tester just don"t know how to use it other than for continuity test

["QUICK-SILVER"]

Check the terminal for temp (green wire) for resistance to ground (sender body, nut head or threads on sending unit). With a guage resistance will vary with temperature. With a light it'll go from no resistance to dead ground when the sending unit is over heated.
I hope it's got a guage, if not you'll end up with jumper wires and boiling water on the stove.

The other two terminals (TCS) should only have continuty between them when temperatures are right. I don't know what that temp is but it wont be that hot when it changes. It's more or less just an on/off switch when the engine reaches normal operating temperature. AND continuity between the two terminals ONLY none to ground (sender body, nut head, threads...) or you'll have a short. Like you've already got. That's why I wonder if it's more crossed up wires or bad sender.

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More
Green temp wire straight to ground is not suppose to blow fuses. It would turn temp light on or peg guage.

Grounding the other wires and fuses will/should blow. So don't.

Just for kicks, maybe waste a fuse, ground out green temp send wire only. Need to know if you get temp light, pegged gauge, or blown fuse.

[darren]

OK on the sending unit the prong where the green wire would go there is no continuty from the prong to the treads or the intake
On the prong where the blue wire would go there is continuty from the prong to the threads and intake
On the prong where the black and white and black and pink wires would go there is continuty to the threads and intake
When I take the green wire at the plug and ground it with a test light to the engine the needle moves to the middle of the gauge and the light on the test light comes on
When I do the same with the blue wire nothing happens and with the key on or off the fuse does not blow
When I do the same with the black wires the test light comes on but the fuse didn"t blow But when I plug the sending unit to the wires and turn the key on the fuse blows

["QUICK-SILVER"]

Temperature terminal should have/has to have resistance to make the guage work.

Test light is what saved the fuse from blowing when you tested the hot wires. I THINK, The terminals for the hot wire should act like a switch from one terminal to another. Definitely obviously shouldn't go to ground through the sender because it blows the fuse.

More crossed wires? Bad sender? This is going to take some studying and I don't think I have the material to figure it out. This may require a service manual.
Do another wire comparison on the old harness if you can.

May try posting in your tech section and see if someone can tell you correct wire locations in the plug.

Good luck
Keep us updated with any info
We'll try to help all we can