The Stovebolt Site Forums The Shop Area The Electrical Bay Backup light switch project -completed !

Finally started working on installing a backup light switch into my SM420 this weekend. Using the following article (Thank you June of Toy4x4s) as a guide as well as emailing the author with various questions, I felt comfortable enough to give it a try.

http://members.aol.com/toy4x4s/hole.htm

Since I have a spare tranny, I removed it's top plate (tower) for this project. Nice to still be able to drive the truck while working on such a project. I think the following folder will give most of you an idea of what I'm doing with a few additional comments.

A few measurements of interest using digital calipers:

Reverse Rod diameter: .623"
Wall thickness: .275"
Space between rod and wall: .152"

A. Take your time in setting up where and how you are going to drill the hole. I also chose the angle approach because there is a little more meat at the upper corner as compared to the top. Also it will be easier to attach the wires from underneath. Besides your tranny cab cover might not allow a switch and wires to extend vertically.

My handy bench drill press was the way to go. Once I set up the jig to firmly hold the tower at the right angle, I was able to quickly drill the hole required for the tap ( 9/16 -18). Lots of cutting oil.

B. Though the original article said that any generic switch from NAPA would work, the switch I bought (Napa #NS119) has made an exception for it is too long. Meaning the threaded portion goes too far into the tranny causing the threaded portion to make contact with the reverse rod in the tower, thus for this switch I had to add some spacers to back it out so the reverse rod makes contact with the switch's button made out of delrin. I could not find a store which had a switch in stock so I've been forced to order something somewhat blindly.

B. This switch's button came factory stock with almost a perfectly squared off end. For this application, you want the button to be either well chamfered or rounded (pic 3). The rod makes a side contact with the switches button, not an end contact. My pic (sketch) #12 helps explain this. Anyway I had to round the end of the button so the rod could activate the switch easier. If it was easy enough, I would love to remove the reverse rod and round the edge of it also so the contact between the two (pic 9) would be smoother and less harsh? Because the button is made of delrin I can imagine that in time, the steel rod's edge is going to wear the button material away. Does anyone have experience in removing and reinstalling the reverse rod? I see that it must come out through the front freeze plug (can't think of a better name looking at it).

C. The space between the rod and wall is very limited so the travel of the button before it activates much be very minimal.

Because the first switch is too long, I have ordered another couple switches to experiment with (all having the same threads) and will pick the least of all evil to do the permanent install.

Stay tuned.

http://community.webshots.com/album/141689703NurJLp?280

Good job Craig!! Thanks for the pictures and information. I too have an extra drivetrain and am interested in the same conversion. I am curious as well on what kind of lights that you are going to use on back. I saw Horvaths set up where he modified front parking lights to act as back up lights. I have even thought about hidden lights that swing down when activated. Just brainstorming. I like to keep my truck original looking, but drive it every day. Keep us all posted and again thanks.
Ralph

I recently aquired a set of supposed 40-53 commercial backup lights as seen the the last shot of my folder.

Don't know where I will mount them. I do like Alan (Horvath)'s idea of using front parking light. Very clean.

Craig

:confused:
I'm getting ready to install a T-5 transmission in my 1937 pickup. Does anyne know if the T-5 has a backup light switch in it? Or a place for one?

Figured out a way to remove the sharp edge on the reverse rod, where it makes contact with the switch, without having to remove it. Just knock out the expansion plug in front by putting a small wrench socket behind the plug in front of the reverse rod. Forcefully slam the tranny into reverse and POP goes the plug.

I then attached a small diameter conical shaped grinding wheel to a dremmel tool and came in via the plug hole and rounded the edge of the rod. Now it's a much smoother and easier activation of the switch.

http://community.webshots.com/photo/141689703/142194968mmoXrG

Hopefully today I will get another slightly shorter switch to experiment with. To me, a switch with a steel button instead of a nylon / delrin button would be ideal. I think it would hold up much longer, but maybe what I've done here by grinding the edge of the rod will give me many slams into reverse.

Hey, Steve

That looks great, man!


[img]http://www.alanhorvath.com/54chevy/chevypics/backup8.jpg[/img]

Alan, how are yours activated? Just curious

With just a push-pull switch under my dash. Simple ... and there only when I need it.

I'm gonna put a lighted switch on it so I'm reminded when it's on, and I'm also gonna add a relay ... but for now, it's working well enough.

What gauge wire should be used to run to the back ?

Big step today. Finally got the right switch from a local auto store (special order or course). It's part number can be either FF2511 or NS71701 depending on who's catalog you are using. The next shot shows the first attempted switch below the shorter (better) one. I still had to round off the button tip for it was also too square, but other than that, no washers required and it works perfectly. This weekend, new modified tranny top goes into place and I'll start installing the backup lights.

http://community.webshots.com/photo/141689703/142609131lkffVs

Assuming a 12v system, 16 gauge would probably be fine, but I'd use 14. In a 6v system, definitely use 14 gauge.

Joe

Hey Alan, actually that push/pull switch is a good idea when someone comes up behind you with their brights on, blairing onto your rear view mirror. You can flip yours on right back at 'em!

Careful,
Let's not cause an accident.

My T5 has a 2 wire hookup for the backup lights so should be easy to hookup. I recently acquired a set of front lights to use with Horvath's methode for mine..
MONGO

KC,
Aren't you suppose to be hanging up your truck tools for awhile for the upcoming family addition????

I'm taking off of work tomorrow in order to install my Tranny tower with switch as well as installing the lights.

Sunset Magazine which is less than a mile from my house is having their annual open house this weekend so I know my better half will be dragging me out from under my truck so we can do our annual ooooh's and ahhh's.

cmayna -- I used the wires that were designated for backup lights, from my EZ-Wire kit -- they are 18 gauge and work fine. I agree with Joe; I would've used 14 gauge, but I guess 18 is good if that's what the pro's use in their kits, eh?

steppenwood -- I agree ... a couple of on/off/on/off/on/off blinks ought to give 'em a hint. These are just backup lights (not spots!) but they're bright and would get attention if flashed a few times I guess.

Alan H,
Did you run a single wire from your switch to one of the backup lights and then jump over to the other light, grounding both lamps bases?

How's your spotlight project doing?

Craig

KC -
Thanks for the info on the T-5 switch. I saw it on the transmission, but it didn't even dawn on me that it would be a backup switch (duh).

cmayna -- You got it ... one wire (from the EZ-Wire kit) runs back to one light (splice) and then over to the other, providing 12v positive. Then I ran ground wires to the frame just to be sure of a good solid ground.

I gave up on the spotlight ... I ordered a new one from the web site THREE TIMES and never got recognized!!! So I decided to skip it for now.

I've been working on my interior lighting. When I got my truck, it had NO interior lights of any kind -- not even the glovebox light. When I put the new AC/Heat unit in I had to custom fit a new glovebox and I put the glovebox light in then.

Last week I put door switches in, so I finally have floor lights that come on when I open my doors, or when I twist my headlight knob -- VERY exciting!!

Then, today, I got a new chrome dome light from Chevy Duty and put that in ... only I'm having trouble figuring how to make it come on via my door switches because the door switches turn the ground on/off, and the dome light operates by turning the 12v positive on/off! I think I can make it happen by using a relay (activated by the door switches) and a second 12v feed to the dome ... I'm working on it.

I just love this stuff.

Alan I replaced the light socket in the dome light with one with two wires, instead of one wire and a grounded socket.

One wire (shouldn't matter which) goes to a fused 12 volts, the other goes to one side of the dome light switch AND to the wire from your door switch. The other side of the dome light switch is wired to ground.

Now my dome light comes on when a door is opened and/or when I flip the switch.

The key is replacing the socket. I used one for a side marker light.

I plan to convert another dome light soon, should I take pictures of the process?

Today I finished my "backup" project. After numerous modifications to a couple different switches, I picked the more recently aquired one with a shorter threaded portion.

This morning, removed the tower off my tranny and installed my extra tower with switch installed. Then ran wires from ignition to tranny switch, tranny switch to rear of truck using 14 gauge wire.

Because the switch is on the passenger side I ran the wire out into the engine compartment and then across and down the passenger side towards the battery. Hopped over to the tranny and then back towards the rear of the truck. The tabs of the switch were a little long so I had to bend them 90 degrees for clearance.

Installing the lights, I had to bore a 3/4" hole for the bulb terminal, followed by the bolting holes. All went well as expected.

Here's an update from my webshot folder:
http://community.webshots.com/photo/141689703/143058211FsMwyo

and the finished product:

[img]http://www.cmaynard.com/Truck/IMG_1633.JPG[/img]

I must say thanks to June of toy4x4 for posting the original topic and pics.

cmayna -- Very cool! Congrats on a job well done!

oldsub -- Thanks for the idea! How do you keep the grounded body of the dome light from providing a ground to the bulb?

I found out how to wire a relay to reverse polarity and use my door switches to send power to the dome light, so I'm gonna approach it that way. I have instructions at my site as soon as I finish (couple of days).

horvath: I used a two wire socket like for a side marker light to separate the light circuit from the frame. One wire connected to 12 volts, the other to the door switches, and the light switch. Since the door switches ground the circuit I changed the light switch so it would ground the cold side of the socket.

I'm probably making this sound more complicated than it is...

I get it.

Here\'s what I did.

That will turn the light on and off when the doors open and close. And if you leave the switch in the circuit you can use it to force the light off, even with the door open.

But if you want to reach up and turn the light on with the doors closed, the switch isn't going to do anything.

That detail was important to me because I wanted a second dome light in the back of my Suburban that I could control independently. Now I can turn on the forward or rear light from the stock switch, or they all come on with the doors open.

However, if you wanted to duplicate the feature many modern cars have, where the dome light stays on a while before going off, either when you insert the key, or after a minute or two, then the relay approach makes it easier to add a timing circuit.

The Mad Electrical stuff looks helpful with the instructions they offer. All Electronics had similar relays for $2.00 each last time I ordered some, though they don't come with the detailed instructions. The same people have some cheap lock actuators too.

You're wiring it wrong.

If you run the power wire from the relay to the BULB-SIDE of the dome light switch, then the dome light will come on with the doors open (you won't be able to shut it off because the dome light switch will already be in the off position) ... then, with the doors closed, the dome light is off ... if you flip the switch on the dome light, it turns on.

There are two power wires to the dome light: One that goes to the switch, and one that goes to the OTHER side of the dome light switch.

Okay. Your diagram didn't show both wires to the dome light, apparently just the second power wire that you must have added.

My approach requires two wires too, though they are used differently.

Right.

A - You wire the dome light as you normally do, with a power wire to the switch - the switch connects and disconnects that.

B - Then you add another power wire from the relay to the "hot side" of the switch - the relays connects and disconnects that.

PS - I just updated my web page ... see what you think:
Update

Resurrecting this post. Does anyone know of a 6V switch?

A switch is pretty much just a switch. A 12V switch will likely work just fine. Low voltage switches are usually pretty robust.

Thx Kevin! Derek

Yes a known 12v switch will probably not care if the voltage is just 6v.