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NSS? Sounds like some serious issues that will still leave you with a butchered looking undecipherable mess. If i were you (and I have been in this type of situation) I would look on the board for a complete under dash and engine harness-uncut and un butchered. They are still out there. Cheap too.
Do you want aftermarket gauges or stock dash?
No all dash lights do not need to be intact to complete the circuit and light the. Several can go out and several will still light.

..........

Quote:

Originally Posted by tonyr0774 (Post 6890621)

Hey fellas,

Hoping a few of you can impart a little wisdom. I am in the process of cleaning up the butchery the PO of my 68 K20 inflicted on the wiring. While tracking down the problem with my reverse lights I replaced the NSS and discovered that the starter portion had been by passed. The PO had unplugged the dual green wire connector and jumped the starter wire directly into the hot wire. I have since attempted plugging the dual green wire connector into the proper prongs on the NSS while connecting the starter wire to the 12 gauge purple wire from the top connector on the firewall.

The result is a little perplexing in that the starter does not turn, however when placing a tester light on the connection while having someone turn the key the light turns on. When I wire it directly back into the dual green wire connector (after unplugging it from the NSS of course) the truck starts right up....in any gear of course! I cannot figure out why I would get a positive reading from the firewall connector but no start. The PO also cut all of the sensor wires from the firewall top connector meant for the temp, brake and oil warning lights and installed aftermarket gauges.

You are mixing the back-up lights and the starter wires and their connectors on the NSS so that I can't follow exactly what you're doing. The starter wiring consists of a purple wire from the key switch to the NSS connector, through the connector to the firewall and on to the starter solenoid.
The starter connectors are at 90 * to each other and the back-up connectors are one above the other.

Attachment 1316198

Attachment 1316199

The light green wire and the dark green wires are connected from the fuse panel and run through the firewall to the rear back-up lights.

I am in the process of re-pinning the connector head but am again perplexed. With all of the corresponding sending unit warning light wires cut shouldn't the temp, brake and oil lights be on?

No, they ground through the sensors and have to be plugged into the cluster to light the lights.

They currently are not and have never been since I've owned the truck. I have already checked to see if they had removed the bulbs on the gauge cluster and all but one are intact....cant remember which one is not. Do all of the warning lights need to be in intact to complete the circuit for all to work when they are supposed to? (its funny, this possibility just came to me as I was typing this).

No they get their power and ground from the key separately and ground from the sensors. Same with the instrument lights except the lights are all powered by the double gray wires and grounded through the cluster housing.

Finally, a two part question. What is the type of silicone used by the factory to seal the harness connectors or a good, safe equivalent. I'm thinking just RTV silicone. I want something that remains soft and pliable. Preferably something even more pliable than RTV silicone.

Check with the forum vendors and LMC trucks for this stuff.

And if I decide to replace my gauge cluster with the later model that has the gauges rather than dummy lights what all is entailed and how much of a PITA is changing the cluster harness if that is all that is needed besides the changing of the sending units?

It is very easy to do but there is a lot of steps involved. I have cited them many times in the electrical forum as have many others. If You type gauge cluster conversion in the small rectangular box up by your PM messages, click the small circle "o 67 to 72 chevy trucks" and click google, it will show you many threads on how to do it.

Any help or feedback would be much appreciated

Here is one of My threads on the conversion. I forgot to mention that the water temperature sensor has to be changed to match the gauge and not the light.
http://67-72chevytrucks.com/vboard/s...d.php?t=588853

vettevet my nss is not hooked up either so i assume my purple wire off the ignition switch is hooked up direct, so i assume that if i cut it near the ignition switch and splice in a wire to go thru the nss that the nss would work properly???

also if i ran a hot thru the back up light connector and to the reverse lights that should fix that problem. i don't know where the harness connects going back to the reverse/tail lights is, i will research that, but hopefully the wire to the back for the back ups is there..... i hate it when someone butchers something up!!!!!!!!!!!!!!!!

Vettevet,

I do apologize for the typo. When I refer to the "double green with connector" I meant to say purple.

Thanks for the help.

IIRC, the purple is the heavy gauge wire that will ultimately be called upon to fire the solenoid and engage the starter.

That wire has to be darned near perfect. Corrosion, a bad splice, marginal neutral safety switch, or pretty much anything that's not near superconducting can cause the solenoid not to engage, causing a no-start. There's no click or anything, just dead. Usually doesn't happen until the engine and starter are hot though.

The idiot lights are usually switched ground, so cutting wires would just prevent them from lighting, not vice versa.

The long and short of it is that the NSS has two circuits - one for the backup lights and one for neutral/park. Green is the lights. Purple is the starter.

Quote:

Originally Posted by hdff (Post 6891177)

vettevet my nss is not hooked up either so i assume my purple wire off the ignition switch is hooked up direct, so i assume that if i cut it near the ignition switch and splice in a wire to go thru the nss that the nss would work properly???

That should work if the truck is starting in gear ,and if the purple wire is carrying current to the solenoid, and not some other wire. It would be best if you can find the purple wire in the harness and cut it next to the NSS, then you wouldn't have to run extra wire.
Also be sure that the NSS is adjusted so that the contacts are closed in park and neutral. My truck was a standard trans so there is no NSS with the automatic I have now. I'll have to install one.

also if i ran a hot thru the back up light connector and to the reverse lights that should fix that problem. i don't know where the harness connects going back to the reverse/tail lights is, i will research that, but hopefully the wire to the back for the back ups is there..... i hate it when someone butchers something up!!!!!!!!!!!!!!!!

Look on the firewall just behind the distributor and there should be a plug with wires in it. That is the connector for the rear lights from the cab. It should have the tails and brake/turns as well as the green backup wire. The dark green wire is the right turn signal/ brake light wire.

Quote:

Originally Posted by tonyr0774 (Post 6892687)

Ok, an update.

As previously mentioned with my initial post the PO of my 68 K20 butchered the engine wiring harness. He cut all of the wires at the firewall connector with the exception of the coil wire. He performed a shoddy HEI conversion where he spliced a 12 gauge wire into the factory wire coming out of the connector. I cleaned that up by re-pinning it with a fresh 12 gauge wire. I re-pinned the following. Oil pressure sensor=20 gauge, coolant temp sensor=20 gauge, starter wire=12 gauge, brake sensor=16 gauge.

That's the clean way to do it. Good for you.

The triple aftermarket gauge cluster has gauges for the temp, oil and amperage. The amperage was never hooked up but my dummy light has always worked.

I'm not sure how the ammeter is wired in those. The water temp sensor is usually plumbed into the block just above the starter, and the oil pressure has the mechanical gauge with the plastic tube connector.

The oil has always and is currently working and the temp used to work but has not worked for some time now. The temp gauge is the type that I have to replace it with a new on that is a sensor, wire, gauge kit. I plan to do this and therefore the original BOSS on the passenger side of the block is and will be occupied by the gauge sensor.

In order to restore the factory lights I decided to purchase a water neck with sensor housing in it. The water neck is aluminum I believe. I purchased a new dummy light sensor, installed it into the new water neck and installed the water neck onto my aluminum Edelbrock intake manifold. The problem is now my temp light in the factory gauge cluster is on and I don't know why. I am fairly certain that my motor is not overheated as it never had any issues prior to restoring the warning light. I am also fairly certain that the thermostat I recently purchased was the correct temp=185 degrees I think. Is the fact that the manifold and water neck both aluminum maybe the cause? I would certainly hate to do away with the warning light considering the time and money spent on fashioning a brand new engine wiring harness.

You should be able to run the temperature warning light off the original sensor in the drivers side head. If the light is on all the time with the key on, either the sensor has gone bad or the wire is grounded at some place. Take the wire off the sensor and see of the light goes off, Key on of course. If it does then the sensor is grounding and you'll need a new one.

The aluminum water neck is not a factor. The sensor might be for a gauge and not the light, they are different so that might also be the problem. Again if you take the temp wire off the sensor and the light goes out then something is wrong with the sensor.

You probably know that the key switch also grounds the temperature light and the brake warning light when the key is placed in the start position. This is a feature the factory used to test the bulbs. They should go out when the key is returned to IGN OFF or ACC.

Also, years ago I installed one of those aftermarket brass proportioning valve. I never concerned myself with the brake sensor given the fact that the wire had been cut by the PO. Now that I have re-wired the harness with the factory plug I have discovered that the plug does not fit the proportioning valve sensor. I will provide some pictures tomorrow to give a better depiction of what I am talking about.

The aftermarket valve may be a different type and possibly don't have the warning light feature.

Any help would be greatly appreciated.

Thanks

Well I figured out the problem. The jack wagons at Oreilly'sold me the sending unit for a gauge set up! Part #WT 203 is what they sold me. I exchanged it for the correct one which is part #WT 346. Warning light is no longer on.

Quote:

The aluminum water neck is not a factor. The sensor might be for a gauge and not the light, they are different so that might also be the problem.

He shoot's he scores!!!! LOL

A quick question on my after market triple gauge cluster. As previously stated my amp meter has never been hooked up. I would like to wire it in so that it is operational but am unsure where to splice it into. There is a negative and positive terminal on the rear of the gauge. I was thinking about splicing the positive into the wire running into the generator warning light on the factory gauge cluster? Is that even right and if so, where would I run the ground to? Would I be able to ground it out anywhere or would it require running it into the ground coming from the alternator?

Any help would be appreciated