FJ40 Dome Light - Quality of Life Mod Using Toyota Parts

[procomsignathid]

Hello All!

This post is for those of you who want to keep a stock look, but either cannot locate a late-model FJ40 dome light with the "door" setting, or want to modify their existing dome light to enable a "door" setting (that is to say, when you open the door, the dome light turns on). I'll let you all judge if the execution is decent, but I was able to do this using all Toyota parts, albeit a bit modified. In my particular case, I have a 1978 '40, and when it was built new, it had a basic on/off dome light, so this may not be for the purists. But I like a visual indicator that the doors are open (especially with kids in the truck), and I wanted the light to turn on regardless of whether the driver, passenger or ambulance door was open.

Here's a pic of the finished result if you want to make the call to read on or not:

Here's a rundown of the parts I used for this:

• 1x 81240-90300 "Lamp Assy, Room" (stock on/off dome light for the FJ40, single power wire, male bullet connector)
• 1x 81240-95A16 "Lamp Assy, Room" (stock rear dome light for FJ60/62, has a lead for power and for ground)
• 3x 84231-28010 "Switch, Courtesy" (pressure switch, uses an M10x1.25 thread to attach to the truck body, switch press = off)
• 4mm bullet connectors (I used Yazaki connectors I had purchased from Toyota Matt and Cruiser Cult, but you could also get them from places like Eastern Beaver)
• 18ga GXL wire. I ordered 50ft of black for the ground wiring (way more than I needed), and used red/black striped for +12v (my truck was missing all wiring to the dome light, you may only need the ground wiring). I ordered mine from wirebarn.
• Wire loom tape (I used Tesa fleece tape from Summit Racing)
• Heat shrink tubing
• Super glue / plastic activator
• Tiny coarse-threaded screws (sorry, don't have details, they were in my hoard of parts... I would suggest rivets instead for a future iteration)
• Hoop connectors

Here's the tools I used:

• Wiring tools (soldering tools, crimpers, snips, pliers, mini-torche for heat shrink tube, etc.)
• Screwdrivers
• Drill / drill bits, including a pin vice for fiddly work (see later on dome light modifications)
• Files / x-acto knives
• 11/32 drill bit & M10x1.25 tap / tap wrench

I should note that it may be possible do this mod using the front FJ60/62 dome light (81240-22070), and possibly get better / more-stock-like results (based on the action of the switch, which rotates like the FJ40 light instead of sliding), but I was concerned about the depth of the mechanism and opted for the integral switch inside the rear dome light. May be a project in the future, we'll see.

I'll split this up into 3 sections:

1. Wiring Plan
2. Modifying the FJ40 dome light
3. Installing the pressure switches

The Wiring Plan
For starters, let's talk about how the dome light will work in this configuration. The pressure switches rely on a connection to ground through the body/chassis, so the dome light must be switched on the ground connection, not the 12v+ source. This is consistent with the current setup for the stock dome light, which also switches ground (which in the stock configuration, is also grounded to the B pillar through the mounting screw). You will need to add an additional lead through the A-pillar, above the door and down into the B-pillar for this switched ground. See the below diagram:

A couple notes on bullet connectors:

• Be mindful of directionality of the connectors (which end is male / female). Toyota designed the stock setup such that if the dome light is disconnected, the loose power lead won't short against the chassis. When we add the new wiring for the switched ground, we need to think in the same way: If you were to temporarily remove one of the pressure switches, you want to ensure the loose connection won't ground against the chassis and turn the light on (when in "door" setting). The above diagram shows the M/F orientation of each lead (look for -> >- notation)
• The additional connectors at the fuse block and below the A-pillar are to allow the hard top to be removed. I found additional points as I ran wiring along the harness (on the engine side of the firewall, and on the interior side under the glove box) that could potentially justify additional connectors if you were to remove parts of the wiring harness. I opted not to add these additional connection points, my thought being that I'll add them later if I need to do major wire harness work.
• The pressure-switches do not come with bullet connectors, to keep it all consistent I converted them all to male bullet connectors, but you could leave them as-is and use the mating connector type (I am not sure of the name of this connector, however)

Here's a couple shots of the dome light, pressure switches and completed harness (for the A-pillar, above-door run, and contains +12v and ground leads, wrapped in wire loom tape):

Note: I did not leave the loom like this, this is just to illustrate the path. The wire loom tucks neatly inside the top of the hard top behind the flange.

 

[procomsignathid]

Modifying the Dome Light
I wanted to accomplish three things with this dome light mod:

1. Keep it as stock-like as possible so that it looks like a normal FJ40 dome light
2. Gain the "On/Off/Door" functionality
3. Use Toyota parts

For starters, I took a look at the innards of the stock lamp to get a lay of the land, and note the dimensions of the switch lever:

The lever protrudes from the body of the light by ~1/2". Also, note the open lug where the mounting screw grounds the light to the body. Now, let's look a the FJ60 light:

There are two rivets that hold that electrical switch to the armature of the FJ60 light (which is then attached to the plastic body with screws). The spacing of the screws is too wide to fit into the FJ40 light, so I will drill out those rivets to use the holes on the switch itself. It turns out to be a pretty good fit for the empty holes on the FJ40 light (see the smaller holes next to the switch lever on the FJ40 light). I also drilled out the rivet on the FJ40 light to remove the lever:

Next up, I wanted to mount the lever from the FJ40 light onto the switch from the FJ60 light. I ended up using what can basically be described as a mortice-and-tenon joint, and this was by far the most fiddly aspect of this project. If you have a pin vice, small files and an exacto knife, this is doable, but take your time. I would not recommend opening up the FJ60 switch further, as the lever is not separate from the switch internals (very fiddly to put it back together). best to keep the unit as-is.

I measured the two switch levers to figure out where to cut, then cut & filed the FJ60 lever down to act as a tenon, and drilled / cut the back of the FJ40 lever to act as a mortice. This took a lot of back and forth, and I was careful not to stress the plastic of the FJ40 lever by forcing it. I kept testing / filing / cutting until I was happy with a nice friction-fit. Then, I roughed up both mating surfaces, and used a plastic-compatible super glue to mate them together:

I started with three holes drilled using the pin-vice, then used a ground-down x-acto knife (like a chisel) to make it into a single hole / mortice.

 

[procomsignathid]

Dome Light Mods (continued)

I should stress that you need to take your time with this step. I had to do a lot of tweaking to make sure that I wasn't going to snap the plastic on either surface, that things were oriented correctly, etc.

You will need to cut away some of the metal on the bulb mount in the FJ40 light to clear the switch (see the top part of the photo). Note the rivet that is visible in this photo (bulb mount, top/right of photo), later on I had to drill that out as I was unable to successfully solder to this piece of metal, and used a screw instead (from the backside), threading into that hole.

For those of you who want to skip the fiddly-ness of this, you could just as easily use the FJ60 switch as-is, however it may be worth painting the lever white to match the lens. Here's that that would look like:

And as noted above, if you want to see what the inside of that switch looks like, here you go (I do not recommend taking this switch apart, as it's not needed for this project. I was curious / hoping to avoid the mortice-and-tenon work described earlier):

Next up is assembly. Interestingly enough, there are tabs to route wires for the later-model FJ40 lights (that had the "door" setting), but alas it is just the plastic frame that has this functionality. We'll use those tabs for our own wire routing.

You'll note the janky brass hoop connector there. I tried to use the existing hoop connector from the FJ40 light (see earlier photos), but I was not able to get the bends I needed and drill a hole through it for it to mate up with the body of the switch (important here, as it saves some wiring: The "on" position of the switch is bridged to the frame of the switch itself to make for an easier connection). After trying and failing to use the existing part, I made one out of some scrap brass sheet I had laying around. If you are careful, you should be able to use the hoop connector from the FJ40 light, just be more delicate than I was.

The "door" position on the switch is soldered to that black/white wire, which uses the helpful tabs Mr. Toyota gave us. A note on the connection to the sprung post which holds in the actual bulb: Try as I might, I could not solder anything to this, and I didn't want to ruin that part lest I lose the ability to hold in the bulb. my solution was to drill out that rivet, use another hoop connector, and screw it to the plastic. It's not ideal, maybe some of you folks could tell me why I couldn't solder there.

I had to create spacers in order for the switch to sit properly on the plastic frame. I made them from drilled zip ties in this case. Just note that the hoop connector that bridges between the metallic switch body and the mounting screw for the dome light has to be on top of the spacer, or you won't have connectivity and the "on" setting won't work:

Here's the finished wiring from the back:

I used tiny little course-threaded screws that I dug out of my hoard of computer-building parts. I think if you had access to the same sort of tooling to do rivets in the same style as the stock light, that would work much better and be real clean, but I am new to the rivet scene. Again, an improvement for a future iteration perhaps.

Lastly, as an alternative to this whole thing, I had considered what the FJ60 light would look like against the B-pillar. For reference, this is how it would have looked. Not bad, but not great, and it would require modification to the body of the light or the B pillar, neither of which I wanted to embark on:

 

[procomsignathid]

Installing the Pressure Switches
The pressure switches require an M10x1.25 thread to screw into the chassis. I wanted switches on the driver door, passenger door and the passenger-side ambulance door (my tire carrier is on the driver side). I didn't feel it necessary to add to both ambulance doors as the kids really only use the passenger side one to get in/out of the truck.

Another big consideration for me is that I didn't want to add holes to the truck that weren't there. Also, my truck being a '78, I do not have the "nubs" on the door to activate the pressure switches, so the stock location for late-model '40s was likely not going to work for me.

In the end, the ambulance door was the easiest. I'm not sure if this hole is stock or was added from a previous owner, but it was already drilled out to around 11/32, and was an easy pick for tapping:

On the driver/passenger doors, I found a small threaded hole on both sides up towards the top of the dash. I have no idea what these holes are for, and they may / may not be present in your truck, but they worked for me. Do note, if you plan on putting the pressure switches elsewhere, make sure they have enough room on the inside to actuate properly. I found some holes in the base of the A pillar near the floor that looked like they could work, but would have required drilling in order to get enough travel for the backside of the switch. Here's the hole I ended up using (same on drivers side as well):

I did some measuring, and was convinced it would work, albeit with some spacers. Here it is after embiggening it to an M10x1.25 thread (pictured to show that this really wasn't much of a violent act, haha):

Here's some minor violence on same hole on the driver side:

In the end, I did need about 1/8" of a spacer for both front doors to get the switch to actuate properly (none needed for the ambulance door). As I don't have access to a lathe, I took some M10x1.25 jamb nuts, drilled the threads out, used another (threaded) nut to hold them into a bolt, and chucked the whole setup onto my drill. After some judicious use of an angle grinder and some files (aka the redneck lathe), I have two convincing spacers, and I don't think it looks half-bad:

I do need to center the plastic washer a bit better, and I think I'll paint the switch (mask off the white plastic part), but once the door is closed you can't even see it (assuming you have the dash cover):

And that's it! It works exactly as it should now, and here's a nice completion shot of the job all finished:

Some lessons learned from this project / how to make it work a bit better:

• Purchase an FJ60 front dome light, that may be an easier mod to combine its internals with the FJ40 light, as it would be a rotating lever just like stock (instead of a sliding lever)
• Learn how to rivet things like Mr. Toyota, so I don't have to hack things together with coarse-threaded screws
• Be more careful when repurposing the FJ40 hoop connector (riveted to the base of the lever) so I don't have to hack a brass replacement together
• Find the proper type of wire colors to make it even more stock

Anyhow, hope this is helpful! Its nice and convenient, and Im glad I went to the trouble. You can thank the South American shop that "restored" my '40 for omitting not only the dome light, but the wiring to said light, and thus set me down this path.

One other fun fact: This '40 is my first Toyota. As a prior owner of Honda / Acura / Subaru, I had initially set down the path of finding a switch that worked as "On/Door/Off" so that in the middle setting, the door setting is actuated. It wasn't until I went down the path of finding Toyota parts to cannibalize for this project that I found Toyotas almost all do "On/Off/Door". I believe this has to do with the simplicity of the switch internals in this configuration. If you don't believe me, try sourcing a single-pole / two-throw switch with a center-off position in this form factor... I couldn't find one (alternatively, it seems SP3T switch is just about as hard to find).

 

[rlong]

That is cool. You’ve managed to “modernize” the 1950’s tech (manual switch) to 70’s tech (door activation)!

 

[procomsignathid]

T

That is cool. You’ve managed to “modernize” the 1950’s tech (manual switch) to 70’s tech (door activation)!

Thank you!

 

[Bad Mojo]

It would appear I've been reading too many threads in the 70 series section and missed this. Great job on the documentation! Having door switched lights are low key really nice I've come to realize after driving a truck with them.

Already saved the parts list for my next parts order.

 

[procomsignathid]

Glad to help! Its been really nice now that Im daily driving the truck.

 

[thatcabledude]

Clean!