millertime_484 Posted January 6, 2022 Share Posted January 6, 2022 Hello, I have a 1986 R688 that I’m getting ready to put to work in the log woods, and I’m having a service brake light issue. When the park brake is set, the brake lights work when the brake pedal is pushed. When you push the park brake knob in, they still work, but as soon as the line is pressurized and the spring brakes release, the brake lights won’t work. This poor old truck has been wrecked 9 times over the years, and 7 of those it was totaled! So, there’s no telling what all is tore up or Jimmy Rigged back together, no offense to the folks named Jimmy… LOL Any ideas would be greatly appreciated! Thank y’all!! Quote Link to comment https://www.bigmacktrucks.com/topic/69027-service-brake-light-issues/ Share on other sites More sharing options...
fjh Posted January 6, 2022 Share Posted January 6, 2022 Hi welcome to the site! Behind the the panel where the buttons are there is a switch with three terminals on it on the park button that switch is likey your issue it lets the brake lights work spring brakes applied and treadle goes thru it when the springs are released! 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69027-service-brake-light-issues/#findComment-486614 Share on other sites More sharing options...
millertime_484 Posted January 6, 2022 Author Share Posted January 6, 2022 Ok, thank you very much! Quote Link to comment https://www.bigmacktrucks.com/topic/69027-service-brake-light-issues/#findComment-486632 Share on other sites More sharing options...
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