Turn Signal Wiring

[aspeltz]

I am attempting to install turn signals on my 85LS. The front signal lights were added new and I plan to use the existing rear tail light / stop light and add an extra wire for turn lights. Is this possible? Also, the wiring diagram for the turn signal switch says to run one wire to the stop light switch. Where is this located?

[Firemack]

ASPELTZ,

The main harness should have wiring for turn signals. it should go from under the dash out to the front of the engine compartment terminal block, and back to the terminal block over the rear axle. The brake light switch is located mid frame near the master cylinder, and has 2 wires running to it, with a pressure switch in the brake line. You should be able to get the wiring diagram from the Mack museum and may be able to read the coding on the wires. Then you just make up the wiring for the front from the front terminal block to the front turn signals and from the rear terminal block to the rear turn signals. I used a classic signal stat switch and turn signal lights which you find at Napa or on ebay or maybe someone on the site has these.

Good luck,

Firemack

[aspeltz]

Firemack,

Thanks for the information. Found the brake light switch. It needed replacing anyway. My parts store actually had it in stock. I could not find the terminal block under the hood so I ran wires direct from the turn signal switch to the front turn signals. The rear terminal block has a terminal for rear hose bed lights, rear battery charging receptacles, right and left tail lights, and right and left brake lights. Which of those terminals should I connect the new turn signal wires? It's very frustrating when the Mack dealerships don't even attempt to help you. I called my four closest Mack dealers; three of them said Mack never made an L model and the one that recognized the L said Mack never made a gasoline engine.

[Firemack]

ASPletz

Most of the guys in the Mack dealers today have never seen an L Model Mack and never worked on a gas burner!

First check to see how many terminals you have on the rear terminal block. Then we can determine if they had an extra set up for turn signals.

Firemack

[Greg Rider]

Do you actually have separate tail lights and brake likes in the rear or is it just marked on the block that way? If they are separate lights I would do whatever possible to utilize both as stop/turn/tail lights. It may as easy as changing the pigtail in the housing. I just like having the extra lighting in the rear for safety reasons. If you are going to do a simple install then you hook up to the existing brake lights. The switch turns this single circuit into a left-right setup so one will be steady "brake" and the other flashes "turn".