M151a1 turn signal switch.

billybob · Post by **billybob** » Wed Feb 15, 2017 9:50 am

Can the M 151 24 volt turn signal switch be used in a 12 volt system? Thanks in advance.

Bobber · Post by **Bobber** » Wed Feb 15, 2017 10:53 am

I think you need to change out the little can that makes it blink. Sorry, not sure of the technical terms. I don't believe there expensive and are still easy to get.

4x4M38 · Post by **4x4M38** » Wed Feb 15, 2017 11:28 am

Rusty, et al.,
Someone documented swapping his M37 to 12 volts that had the military
turn signal setup. If I recall correctly he just disconnected the military
flasher and replaced it with a common 12 volt jobbie.

Otherwise everything else was ok.

Take care,

Post by **wesk** » Wed Feb 15, 2017 12:39 pm

The transistorized control assembly on the M151's turn signal system is 24 V period. If you intend to convert a jeep to 12 volt the easiest path is a standard 12 volt aftermarket switch kit. The military switch & control box are rather expensive. The switching of the flasher does not guarantee the remaining transistorized circuits in the control box will function correctly or last very long. Operating electrical components at lower than design voltages generally results in excessive heat buildup.

This is the standard late system used on the M151's

The early 50's M series turn signal system control box is also 24 volt period.
The mechanical relays in the large control box can be switched to 12 volt units but it is a lengthy modification.

The early 1950's system

Most of the voltage sensitive parts will have to be replaced with 12V parts. Not a small task if you count all the voltage/current sensitive parts in the diagrams.

The simple 12 v turn signal system is the best answer:

billybob · Post by **billybob** » Wed Feb 15, 2017 2:08 pm

So I'm assuming if I use a 12 volt flasher it still wont work. I believe my unit was made in 67. I have a new universal unit but I wanted the military look. I'm going to play with it and see what happens. As always, Thanks Wesk for all the good info. I have your wiring diagram which is very helpful.

4x4M38 · Post by **4x4M38** » Wed Feb 15, 2017 6:48 pm

Hello Wes,
Here is the link to the M37 swap to 12 volts. He installed transistorized
unit originally, then simply swapped to a 12 volt flasher and 12 volt bulbs
and kept the 24 volt turn signal controller.

http://garbee.net/~cabell/12voltconversion.htm

Take care,

billybob · Post by **billybob** » Wed Feb 15, 2017 9:01 pm

Thank you 4x4 member. My M38 is already switched to 12 volts so I think I'll try it with a 12 volt flasher. Thanks again for the good info.

4x4M38 · Post by **4x4M38** » Wed Feb 15, 2017 9:36 pm

Open the link. There is a specific way to hook up the flasher that is different
from the 24 volt flasher. Nothing complicated.

billybob · Post by **billybob** » Wed Feb 15, 2017 10:44 pm

Yes I remember seeing that. I printed it off so I can go back over it. Thanks again.

4x4M38 · Post by **4x4M38** » Thu Feb 16, 2017 7:47 am

As with the information presented here by members and admins,
there are numerous sites out there that others have taken the time
to document and post. And while may not be vehicle specific to our
Jeeps, still have a wealth of information. The Garbee M37 site mentioned
is one of those.

I've read through most of his pages but his electrical and turn signal
topics are very good.

Take care,

billybob · Post by **billybob** » Thu Feb 16, 2017 9:20 am

I really appreciate all the interesting info I've received on this subject. I've built a test station so I can test three different turn signal systems I've acquired. I'll let you know if the military switch will work or not. Thanks again.