Need some electrical diagnostics help

Have you tried every switch one at a time to see if they may be on another switch? @Brettj3876 does Mack use more than one switch?
For the back up alarm there’s a switch on the transmission,it should be on top near the shift tower. I would start there and work back if good.

 

Macks are known for crappy grounds. Start there.....and the mess of wires you have back there. We really haven't had issues with wiring thankfully. Pain in the ###. I will say this tho, the wiring on the 93 is a lot better than the 99. Volvo had their hands deep in the cookie jar when the E-tech was released compared to the older E-7s

Do you have the wiring schematics? Marker lights should still be on 1 switch. Not 100% but I think it's still like the older ones from early 90s on up

 

Can't help with the backup beeper.



On the rear 2 yes that's correct and same with turn signal markers. When you flip the marker light switch all the others should come on I would think

Off topic, but how's the rest of it. Jake's work? The E-techs have a habit of losing the plug on the rocker shaft and not getting proper lubrication to the head for the jakes to work. Had that happen 2x now, tac welding the plug in fixed it for good. They're finicky on overhead adjustments.


What hp

 

Since you have a dump box I'm not sure how they wired them up.

Headlight switch 1 click./ Turn signal marker and the 2 tail lights should be on.

Marker light switch/ the 5 up top should be lit on the cab

Sorry for the confusion

 

If the wiring is a mess, I'd consider starting fresh. Put a new junction box in at the back and run all new wire to everything. Patches on top of patches just leads to constant and never ending headaches.

 

That's what I would do. No telling what they could of rigged up. You'll just end up chasing problems forever.

Was it a dump from the factory?