1988 Mack RD690s reverse light switch.

[Casper1988]

I am very close to getting my truck sorted out and have to finish a few minor things for inspection. One being a back up light to pass , I see the switch on top of the tranny ( 2070 ) maxi-torque and see the two wires coming off and the go back towards the engine and Into a harness up to the firewall. Very hard to follow. Is there a schematic or should they coincide with a # on the connection board on the firewall. I haven't broke out the test light yet but will soon to determine if the switch is working.  Thanks .

[j hancock]

This is earlier than your truck but the basics are the same.  The lower left of the diagram shows the switch and lights.

https://www.bigmacktrucks.com/applications/core/interface/file/attachment.php?id=85142

In this example, the #4 post on the inboard junction block is power to the trans. switch and the #5 post is to the back up lights.

[Casper1988]

Thank you Mr Hancock. I could wire off the switch I suppose. Think I will start with a fresh switch anyways. I am involved in another project with the old girl. A brake job turned into bearings again. they must be the original bearings ( 116,000 original miles ) cause the inner bearing was so loose she fell apart on disassembely. Inner bearing keeper was stuck to the spindle bad and required a porta-power to pop it. The seal was on there good to. Spindle was fine after clean up.