M38 MC Light switch problems

[daniel.7575]

Hi everyone,

We've just finished a rebuild on an M38mc and we're having some issues with correct rear light function.
Marker lights work fine, but only LH stop light works. Have checked wiring (new harness) and all appears to be correct.. when I switch to BO drive then the RH stop light works we cant get both to work at the same time..
The light switch installed is a more modern 3 lever type from a later M series truck as we don't have an original.. does anyone know if these should work correctly in the M38 or do I need an original unit?

Many thanks,

Daniel.7575

 

[daniel.7575]

Just found that rear lights have separate operations! so the jeep is setup to show only one stop light in either service or blackout settings!
Looking at wiring diagram were going to try connecting 20 + 23 together and I think this should sort it?!

Pays to read your manual!

 

[ReoRider]

Keep in mind that the service lights and the blackout lights are separate circuits. The early "M"series trucks followed the WW11 pattern of left side tail light with service tail and stop on top and B.O. marker on bottom. The right side tail light had B.O. stop on top and B.O. marker on bottom. You don't want to connect the two systems together as you will have extra bulbs with little effect.

Most restorations switch out the right side tail light with an additional left side version, giving you service tail and brake on both sides. This is connected in parallel with the existing left side light. You then loose the B.O. stop light on the right, but gain the needed modern lighting. When the military did this conversion they added a single bullet B.O. light on the right for the stop signal.

Just finished a 1952 MC here- great fun.

Hope this helps.

 

[bikeman]

Yeah, only originally driver's side tail light. I don't have a wiring diagram, but sounds right.

 

[4X4M38]

Daniel, over on the WillysMJeeps site we have the pinouts for the wiring harness as well as wiring diagrams to convert to two left tail lamps and add the bullet black out stop on the right. That is essentially a change in prep for adding turn signals. Brian