Stock Tail Lights

[AN/GRC-46]

I can't find any references that explain the functions of each of the lenses in the standard M37 tail lights.
The left one has a large oval lens which lights red when the headlights are on, and brighter red for the brake light. The right one has a depressed oval area with a square cutout lens. None of my light switch settings do anything with that light. What is it for?
Also, both tail lights have a horizontal lens opening below the oval part. This has red lights that come on as running lights. Is this correct?
The wiring in my truck has been changed a bit and I'm not sure everything is as it should be, lightwise.

 

[MWMULES]

This should help

 

[AN/GRC-46]

Thanks MWMULES, that is what I was looking for. However, I don't know if I'm reading it right or not. It looks like, no matter what position the switch is in, ALL the rear lights are lit. I would think that driving lights would be one combination, parking lights would be different and blackout lights would be something else. Is the Stop Light different from the Blackout Stop Light?

 

[73m819]

it all depends how the 3 lever switch is set

 

[AN/GRC-46]

Still Confused

it all depends how the 3 lever switch is set

That's what I would have thought, but from the diagram, no matter what position the switch is in, both rear lights appear to be on. I can't tell from the picture what bulbs are lit - the top (in the oval) or the bottom (in the horizontal slit), or all of them.

I drove one of these (that's it, over to the left) for 17 months in the service so I probably should know what's up, but I rarely drove at night and wasn't much concerned with what was going on behind me. Now, with heavy traffic and sometimes overactive police, I want to be sure everything is as it should be.

I'm okay on the front lights; it's the back I'm confused on. The light switch has four positions; what bulbs should light when the switch is turned to (1) Blackout Marker, (2) Blackout Drive, (3) Service Drive and (4) Service Drive. Also, under what conditions would the vehicle be driven with the switch turned to Stop Light?

 

[Oldfart]

Stop Light is for normal daytime driving. Nothing else works except the stop light when the brake pedal is depressed. (only one of these on the left rear.) Blackout Marker should light up all 4 of the rectangle lights. Blackout Drive should light up the Blackout Marker lights and the left front light with the shield to deflect the light down. There should be a position for the park lights and then a position for head lights. As I recall, the park light position should light up the right rear rectangle in the oval. Getting old here and hard to remember. I think the SS TM's might include the operators manual for the M37.

 

[AN/GRC-46]

Thanks OldFart. I think I see what's what now. It seems my lights are doing their own thing. The only ones that do what they should are the only ones I really need - the headlights and the left brake light. I guess I have some tracing to do.

As far as the brake lights - is the right brake light red? And when pressing the brake in blackout position, do both brake lights light, or just the blackout brake light?

 

[Oldfart]

I don't know what is correct, but I don't have a brake light in the blackout position. The only light that funcitons as a brake light is the left rear red oval lens. It is my understanding there were a few in service conversions to the military turn signals. I have seen rear lights with matching left and right assemblies. Don't know if that was done by the civi buyer or the military. The early parts M37's I bought in the 60's/70's (50's vintage trucks) are set up like my driver. I don't know what the Vietnam vintage setup was.

 

[nattieleather]

On the back of your truck:

On the drivers side you have one normal service brake/tail light and one black out marker light.

On the passinger side you have one Black out Stop light and one black out marker light.

When you take the main lever and click it one click to the right you will have one brake light only. This is for normal day time running. If you click it two clicks to the right you will have head lights and tail light and normal brake light. The tail and brake will be on the drivers side.

Now if you take the lever in the middle position and click it one click to the left you will have black out marker lights. The light in the front of th truck as well as the little red bar lights at the bottom of both rear lights. Also if you push on the brake peddle the little square white light on the passinger side will come on indicating you are applying brakes. It is your brake light in black out mode. If you click the lever two clicks to the left the black out drive light on the front fender will come on and be your "headlight" for black out conditions.

Black out means tactical not to be seen low light conditions.

How the marker lights work is really interesting. The black out markers are made up of four slots that would looks something like this " ". If you are traveling the correct distance from the vehilce in front of you the black out marker (i.e. tail lights) will look like this | | (two bars. If you get to close they look like this " " (four bars) and if you are two far back it will look like - (one solid bar) This allows you to maintain distance when you can't see the truck infront of you because it's pitch black in the woods.

I hope this helps you understand your lights a little better.

 

[Oldfart]

Thats how mine work except I never had a black out stop light. Thanks for the info. 45 years I have owned my M37 and I never knew that level of detail. ~~ So how do the replacement or later tail/marker lights deal with black out?

 

[AN/GRC-46]

Great explanation! Thanks again for helping make sense of what should have been obvious, but isn't.

Just one final question: on the front of the truck in the smaller housings, you have Parking Lights and Black Out Marker lights. Why "Parking Lights" and what purpose do the front black out lights serve?

 

[majorhitt]

I don't have the book in front of me, when traveling in black out conditions the front black out lights are for the vehicle in front of you to know where you are. The TM shows how the lights would look at different distances between vehicles.