1974 Mack R600 brake light issues

[MackRookie]

I am working on my future father-in-laws 1974 R600 with him.

The other day when we hooked a dump trailer to the tractor we couldn't get brake lights on the trailer. The dump trailer had worked correctly with other trucks hooked up, so the problem wasn't the trailer.

The problem only occured when the parking brake and tractor protection knob were in drive mode. We deduced that the problem was either in the wiring or the plumbing of the pressure switch of the tractor protection knob. Can anyone supply me with the correct hookup for this assembly? The three terminals on the switch are labeled IGN, TTR, and TLR. The valve had 2 delivery lines and 1 exhaust.

When we switched two of the wires, the lights worked correctly when in drive mode but not when the tractor protection knob was out.

Also, did this model have a feature where the brake lights in the trailer come on when the pressure is insufficient to take the brakes off?

Thanks for any help.

[thomastractorsvc]

Check in the wiki for the wiring diagram I have seen it there

[MackRookie]

OK I see a wiring diagram for a 1983 mack truck and it looks similar to what we have. Thank you for the help. Is there also some resource that will let me confirm that the piping on the valve is hooked up correctly or a troubleshooting guide for this system?