M101 lighting ?

[Wtrfwl havoc]

I am sure this has been beat like a dead horse, but I have an 89 m101. Does anyone know is all M101s were 24 volt or were some of them 12volt? Mine looks like 12 but someone may have changed them and I have another problem?

 

[Wtrfwl havoc]

Also the lights have two bulbs on them. One dual filament I assuming for turn/brake and tail lights. The other is a smaller single filament. Anyone know what that is for? Sore for the dumb questions. I am new to the military stuff but becoming an enthusiast lol

 

[Chief_919]

The 101's left the factory with 24v bulbs but unit who towed them behind the M1008 series vehicles often changed them out to 12v bulbs.

The only difference in the 12v and 24v ones in military service was the bulbs.

Your lights should have 4 bulbs. The bottom 2 are blackout and of no concern for regular use. The top two are your regular lights, the top bulb is the parking lights, the bottom is the turn/brake light.

If they are 24v bulbs the top will be a 623 and the bottom will be a 1683. If it was swapped to 12v they could be a number of part #'s but most common for the top is a 631 and for bottom is an 1156- but there are others that will fit and could have been used.

 

[DeadParrot]

At least on my 101, both of the top two bulbs per side came with dual filament. They are NOT dual purpose bulbs but instead a redundancy feature so a single filament can fail and the bulb still provide light. The smaller bulb is the running light and the larger one is the brake/turn light. The 12V sub for the larger one is a single filament 1156, often sold as a backup light bulb. Don't remember the sub for the running light.