The Stovebolt Site Forums The Shop Area The Electrical Bay Interior Light Door Switch

On my 1950 3600 the original interior light has a power feed wire and an light mounted switch.

As part of my new wiring harness there are two wires for the interior light, one power and one ground where the ground is intended to be switched by a door switch or the light switch (also came with the harness).

I am curious if others have already determined what is required to modify the dome light to add a door switch feature?

I think the door switch and the wiring would be fairly straight forward but I think the base of the light socket is not isolated from the base-mounting bracket portion of the dome light with the light mounted switch turning on/off the power to the lamp. So in order for the door switch ground to work the socket will need to be isolated from the base.

I may not pursue this but if I am ever going to make this modification this would seem to be the time.

You are right about the stock cabin light socket being grounded.

How much modification are you interested in doing?

You will have to change the door switch to high side switching instead of low side switching. If you don't already have door switches, you can get normally-open 2 terminal ones fairly easily.

If you want to make that change, do you want the lights to come on when the door is open OR the current switch is on? Or do you want them to come on when the door is open AND the current switch is on?

In the latter case, the existing switch acts as an override for the door switch.

If you like, I can draw you some schematics for how to set this up.

Yes, I am having the internal debate about "would this make sense to do" but I would rather make a decision before I wire the light than after.

My understanding is that the wire harness I am installing is set up for a more modern vehicle with the door switch and headlight switch providing 2 options to provide the ground to complete the circuit for the light to come on. The light has power provided to it all the time (just like standard). There are two wires designated for the "dome" light, one that would provide power and the other that would provide the ground path. The headlight switch came with the harness. I would need to detemrine how the harness intends for the door switch to be wired but my preliminary read indicates that the harness intends the installer to have these two options (door or headlight switch). The harness instructions are fairly good but there is not a wiring diagram per-say so it is not clear to me how the headlight switch and door switch are intended to work in parrallel othe rthan the headlight switch body does need to be grounded for the interior light feature to function (per the instructions).

I do not have a door switch unless I can "steal" one from my son's '88 Fiero parts car that I am storing.

If I do proceed I would want the light to come on when I open the driver's side door (not doing the passenger side), or when the headlight switch is rotated to the position where the interior light would illuminate. I would either eliminate or always leave on the original light switch that is part of the light assembly.

I am assuming that given that people are installing power windows, power locks, and all other forms of "modern" features that I would not be the first person to do this so I am trying to learn from others that have done this to decide if its what I want to do.

If I decide to forget about the door switch I will use the power feed wire and original switch on the lamp and leave the second wire out (probably trace it back and delete to avoid any problems).

Your dome light comes on when you rotate the light switch? Mine only has the switch at the light itself.

Otto, that is a "feature" of the new light switch that came with the new harness if I understand correctly. I am in process of installing the harness and nothing has power yet to determine when lights actually come on.

Guitplayer, I understand your point and may just drop the whole idea.

I am so use to just reaching up to turn the cabin light on.

Yes, thats how I would like mine to be instead of at the switch. 58/59

WICruiser,
Attached is my crude diagram of how I addressed the dome light on my “48”᠁.like you I couldn’t leave well-enough alone. I was going to just PM you with my schematic and avoid all the dissecting and drama that the group might otherwise inflict, but what the heck. I must advise that I built my own harness from parts and pieces of mostly GM 80ish vehicles and used a 1980ish GM headlight switch along with following a 1980ish GM Shop Manual. I put a 6-1-13 date on the diagram᠁.so excuse me if I’m unable to clearly field any questions you might have. Good Luck, Dave

I'm spoiled. '51 Suburban, so I open a door and footwell lights and rear lower wall lights come on. The original dome is still OEM. In the back I have a flood hooked to the door switches, but also on a switch I can control at the rear.

Flatblu4748, thank you for the diagram. More elaboate than I was thinking with the key warning buzzer but I bellieve I understand the basics for the interior light. I still need to detemien what would be invovled in isolating the dome light mounting bracket from the bulb base.

MNSmith, those footwell lights seem like a nice option to consider and could easily be wired in using my harness connections for the dome light using the same power source and door switches/headlight switch to turn them on.

For the moment I have about 100 other wiring related tasks so this one is pretty far down the list.

Okay so now I trying to run the wire that goes to the interior light and I can not seem to get it routed up the "A" pillar of the cab. Is there a trick to getting the wire through (I knew I should have pulled a string through when I pulled out the original wiring months ago).

I have not done it on a 50 cab, but on other similar vehicles I took a piece of stainless safety wire or a chunk of mig wire, folded the end back to make a 1/4"ish rounded end and fished that from the top.

I have gotten in the habit of pulling a string into anything that I fish even if I don't think I have anything else left to pull.

I've used a speedometer cable with good results.

Thanks for the quick feedback.

I tried running a welding wire down from the top but I did not try bending the end to make it more rounded - I will try that next.

I will also look at the factory assembly manual as I believe there is a cross section of the "A" pillar that may provide some additional clues.

I have an electrician's fish tape that I bought for another project. It works well for that kind of stuff. But I think I was able to fish the wire through all by itself from the top. The hard part was getting the wire between the two panels at the rear to the light. I must have spent an hour or more attempting to fish it through with the fish tape and a coat hanger. I finally just tucked it over the top of the inner cab panel.

Cruiser: it’s been awhile since I fished my wires thru that “A” pillar᠁I remember being very frustrated too, it’s difficult but not impossible᠁.trying going both directions: from the bottom up and/or from the top down. A coat hanger worked for me. Good luck, Dave

I tried a welding wire with a loop on the end from the top again and beleive that I am getting far enough but the end appears to be exiting into the space between the inner and outer cowl rather than into the interior cab space. I thought I should be able to find the end with my finger extended into the area above the inner cowl but so far no luck. I hope to have time to try again this afternoon.

Perhaps this photo attached will help

back side of the dash showing the bottom of the a pillar
The blue wire is likely a replacement for the cab light wire and you can see the factory wire clip that’s would have held the original cab light wire going up into the pillar
-s

I recall having that issue. I think if you stick your pull wire up from the bottom and then tie the dome lamp wire on to it and pull it down thru the pillar, you'll have better luck.

Here's another photo of that area (minus the cobwebs. )

I was finally able to get the wire pulled through the A pillar.

Previously when putting the welding wire down from the top I was getting into the inner/outer cowl space rather than exiting into the interior of the cab.

I did not have any trouble in the rear panel area, there was a section of the area that had been formed away from the rear panel providing relatively easy access for the wire to run to the light opening area.

Thanks to all those that helped with this effort.