Brake light Problem

[ozzieM715]

Hi there...I have got a fair amount of work done on the M715 so far, have replaced brakes.Am very happy how the standard brakes stop..
Rebuilt fuel pump,new water pump,had the radiator done,new wheel bearings all new hoses,new tie rods,

The truck drives great as it had been sitting for 20years and i didn't know what condition it was in..so i am up to getting some lights working so i can get it road registered ..the truck is completely original nothing on it has been touched . i I was very lucky as everything works except for the brakes lights..i tested the hydraulic switch and it is working fine .

So does the power then go back to the 3way switch? i have looked at the wiring diagram but I've got no idea..i have no brake light power to the rear ...thanks for any ideas cheers Mick

[brute4c]

One is live all the time when the switch is powered, so there should be power at one terminal of the brake light switch. The other terminal is live when pressure in the brake system occurs thus closing the switch. Then power returns to the 3 lever light switch and then it leaves the 3 lever switch on pin C and runs, in the early style turn signals, to the Distribution Box as the wire with the ring terminal marked B. The power out to the brake lights from the Distribution Box is as follows:

Wire E: Right rear turn signal/brake light feed.

Wire K: Left rear turn signal/brake light feed.

Hope that helps...

[MrNeutron]

Just needed to mention the obvious, make sure your dash switch is turned on so that the brake lights will function. Next just trace the power and ground all the way to the brake lights.

[ozzieM715]

Wow thanks guys great info..very knowledgeable..will do a full trace back but at this stage it looks like it is in the 3 lever switch will try the switch out of my M38A1 they seem the same????

[brute4c]

If you have a known good one, that is one way to go...rule it out or find the problem...ask more if ya need.