Reverse light wires

[Montierth]

When I got my truck it didn't have a neutral safety switch and it does not have the purple wires. However, it does have the light and dark green wires shown. They are plugged into a block with a spring in it. Are these the backup lights wires? What is the spring block thing?

[External]

Subscribed.
I have the same thing going on.
Really want to have back up lights!

[Montierth]

I unplugged the spring block and tried the jumper wie trick to see if I could get the reverse lights to come on but no luck. Although I admit I am not sure if the bulbs are good or if the wiring is grounded properly. However, I have seen other photos with the same green wires and the spring block thing but no explanation of what it is or why the reverse lights are plugged into the block thing.

[LockDoc]

Originally Posted by Montierth

When I got my truck it didn't have a neutral safety switch and it does not have the purple wires. However, it does have the light and dark green wires shown. They are plugged into a block with a spring in it. Are these the backup lights wires? What is the spring block thing?

What transmission do you have?

LockDoc

[Montierth]

Automatic Transmission is turbo 350. I'm guessing originally truck was standard on the column due to no purple wires?

[Andy4639]

First thing. The part I circled in your picture is in fact the neutral safety switch and backup light switch. The wires should be hooked to it so that when you put the truck in reverse the column linkage moves the internal part of the switch to put power to the lights.

So first thing is unplug that jumper box and see if when you have the truck on do you have power on one of the green wires which you should. Then touch it to the other one and the lights should come on.
If not you need to find out why you don't have power to that wire.

You will also need to test the switch to make sure it works also. This maybe why they didn't use it.

Once you have power to the one wire you can then see if the switch is good by:

You have to adjust the switch to the right spot to get power to both wires. In other words put the truck in reverse without it running but turned on. Then loosen the 2 screws on the switch that's circled to see if you can get power in to go out to the lights.
Here is a picture of the switch. The one on the right is the truck switch but you may have the van switch.

[Montierth]

Thanks for the response. I bought a new NSS to replace the old one. To test the green wires with a tester or with the jumper wire does the truck need to be running or just the key turned to start position?

[Andy4639]

Originally Posted by Montierth

Thanks for the response. I bought a new NSS to replace the old one. To test the green wires with a tester or with the jumper wire does the truck need to be running or just the key turned to start position?

You just need it in start but not knowing your truck I can't say 100%. Take that jumper box thing off and try it with out starting it and then go from there.

[Montierth]

Cool. Thanks so much. I ordered some new bulbs that come in tomorrow. I'll check it tomorrow after work.

[Montierth]

Once I get this figured then gotta figure out headlight relays for 4 headlight GMC. May just buy it for $30.

[Steeveedee]

To test the backup light portion of the switch, the should be in the "Run" position.

Whichever way you go on the headlight relay (DIY, kit) it is a great upgrade. You will be pleased with the results. I didn't want to run around sourcing parts, since my time is worth more than the $30 I spent for the kit.

[Montierth]

Perfect. Thanks!

Yeah for $30 I think it is worth it. Then just gotta decide on headlights. Trying to get my truck on the road by next weekend.

[BigBird05]

I'm doing this from memory, but didn't the three speed trans have a back up switch mounted on the trans?

[Bonestock3ott]

My 3OTT has the reverse switch on the column, I believe the silver block that the wires are attached to in the picture is the reverse switch that the mounting bracket is missing from and probably the plastic lever (tab) that went into the column to activate the BU lights has been sheared off from not being adjusted properly at some point when in use before the column and tranny swap.

[Montierth]

Originally Posted by Bonestock3ott

My 3OTT has the reverse switch on the column, I believe the silver block that the wires are attached to in the picture is the reverse switch that the mounting bracket is missing from and probably the plastic lever (tab) that went into the column to activate the BU lights has been sheared off from not being adjusted properly at some point when in use before the column and tranny swap.

That kind of makes sense. I have seen a couple pictures on here that look like mine with the block. If you look closely on the block it looks like there is a broken off tab.

[Andy4639]

Most old 3 speeds have the switch inside the transmission case as stated. When you put the truck in reverse it activates the backup lights. From his picture though i figured it's a automatic. plus the fact he says about the neutral switch which 3 speeds don't have at all.
So if the truck came stock as a 3 speed on the tree there want be a neutral safety switch.

[Bonestock3ott]

Here is the part # for GM 3ott reverse light switches GM 3745921. EBAY LISTINGS say they were used from 1958 to 1972 and they mount to the steering column.

[Montierth]

With all your help I was able to find this post.
http://67-72chevytrucks.com/vboard/s...d.php?t=536776

This shows the bracket the spring block switch attached to. It also shows the tab that broke off my spring block switch that would have attached to a 3 on the tree column.

This has taken me a long time to figure out. Thanks guys! Now I hope there is power there so I can plug into a neutral safety switch.

[Montierth]

One more. http://67-72chevytrucks.com/vboard/s...d.php?t=725138

Rebuilding a 3 on tree column showing the part. http://67-72chevytrucks.com/vboard/s...d.php?t=330513

[Montierth]

2 pics from the 2nd post

[zosoppp]

Originally Posted by Montierth

This has taken me a long time to figure out. Thanks guys! Now I hope there is power there so I can plug into a neutral safety switch.

there is a B/U Lamps fuse in the stock panel, see this thread for fuse panel photos.

http://67-72chevytrucks.com/vboard/s...32&postcount=2

[Montierth]

Originally Posted by zosoppp

there is a B/U Lamps fuse in the stock panel, see this thread for fuse panel photos.

http://67-72chevytrucks.com/vboard/s...32&postcount=2

The fuse is good. I got my ohmmetter out and was able to determine determine that I have power all the way to the firewall. This weekend going to test from firewall to rear plug.

[zosoppp]

Originally Posted by Montierth

The fuse is good. I got my ohmmetter out and was able to determine determine that I have power all the way to the firewall. This weekend going to test from firewall to rear plug.

Don't forget to check the grounds (where the reverse assembly screws into the rear of the bedside) too.