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As promised, here's a thread on upgrading the gauge back lights with drop in LED bulbs and lenses, without modification to the original wiring or bulb sockets. While I'm working with a M939 vehicle here, other M series vehicles that use the same bulbs sockets and lens can also benefit from this. Taking pictures of lights in the dark doesn't work well so you'll just have to take my word on some of this.
To start, we need a baseline for comparisons. All of my gauges are new with perfectly clear cases in the back and perfect lenses in the front. Basically, the best possible scenerio for lighting the gauges. If you have not cleaned the back casing and windows for the gauges, this can drastically affect how much light enters the gauge. I had swapped the red lenses out for some green ones, since green lit the gauges better with incandescent bulbs, so that is what I'll be comparing against.
The military supplied an upgrade kit for HMMWVs, that included an LED bulb and new lens, in an attempt to remedy the problem of swollen lens caused by the heat of incandescent bulbs. This kit is referenced in PM Magazine and all the parts numbers are included in the screenshot below.
You'll need (10) 1/4" spacers and (10) 8-32 tpi x 1/2" long screws for the sockets. After the spacers are installed, the bulb of choice can be used and the new lens is screwed in normally. The seal for the lens with fit as intended against the panel to keep moisture and dust out.
This is what the kit includes. You can also just get the lens or just the bulb.
This kit will work with other vehicles, but the lens is longer than the standard lens, so the socket will need to be spaced back from the panel to accommodate this. The longer lens is the key here as it gives you a larger area to let light through to the gauges.
The problem with using LED bulbs with the stock lens is that by design, the LED diodes aren't in the small area where light can exit the lens. There isn't enough "spill" from a diode, since they are so directional, to make a useful amount of light either. The longer lens puts the diodes of the bulbs in the area where useful light can make it out. Here's a comparison shot of old vs. new.
The new lens is exactly 1/4" longer, so that gives light 1/4" more room to exit. To accommodate this extra 1/4", I used spacers and longer screws between the back of the panel and bulb sockets to take up the extra room. Without the spacers, the lens just stick out the front of the panel and does nothing to help on the back of the panel. This is the modification part of this: screws that are 1/4" longer and 1/4" spacers. That's all that will need to be done to make the new lenses work. A comparison of a socket without spacers on the left and one with spacers on the right.
In this picture you can see the spacers. Don't mind the bulb I had in there. I was doing trial and error, and there was more error with this style bulb. More on that later.
To start, we need a baseline for comparisons. All of my gauges are new with perfectly clear cases in the back and perfect lenses in the front. Basically, the best possible scenerio for lighting the gauges. If you have not cleaned the back casing and windows for the gauges, this can drastically affect how much light enters the gauge. I had swapped the red lenses out for some green ones, since green lit the gauges better with incandescent bulbs, so that is what I'll be comparing against.
The military supplied an upgrade kit for HMMWVs, that included an LED bulb and new lens, in an attempt to remedy the problem of swollen lens caused by the heat of incandescent bulbs. This kit is referenced in PM Magazine and all the parts numbers are included in the screenshot below.
You'll need (10) 1/4" spacers and (10) 8-32 tpi x 1/2" long screws for the sockets. After the spacers are installed, the bulb of choice can be used and the new lens is screwed in normally. The seal for the lens with fit as intended against the panel to keep moisture and dust out.
This is what the kit includes. You can also just get the lens or just the bulb.
This kit will work with other vehicles, but the lens is longer than the standard lens, so the socket will need to be spaced back from the panel to accommodate this. The longer lens is the key here as it gives you a larger area to let light through to the gauges.
The problem with using LED bulbs with the stock lens is that by design, the LED diodes aren't in the small area where light can exit the lens. There isn't enough "spill" from a diode, since they are so directional, to make a useful amount of light either. The longer lens puts the diodes of the bulbs in the area where useful light can make it out. Here's a comparison shot of old vs. new.
The new lens is exactly 1/4" longer, so that gives light 1/4" more room to exit. To accommodate this extra 1/4", I used spacers and longer screws between the back of the panel and bulb sockets to take up the extra room. Without the spacers, the lens just stick out the front of the panel and does nothing to help on the back of the panel. This is the modification part of this: screws that are 1/4" longer and 1/4" spacers. That's all that will need to be done to make the new lenses work. A comparison of a socket without spacers on the left and one with spacers on the right.
In this picture you can see the spacers. Don't mind the bulb I had in there. I was doing trial and error, and there was more error with this style bulb. More on that later.
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opcorn: Interested in what you've got for Part Two! 
