DiamondK Posted March 31, 2020 Share Posted March 31, 2020 I have an RD688 in the shop. I have found three different air switches. two of them turn on the brake light and low air light when crossed with jumper. one does nothing. it is on the back of the blue brake valve. is that where i should be looking for the problem of no brake lights with service brake? Quote Link to comment https://www.bigmacktrucks.com/topic/61802-1998-rd688-service-brake-light-switch/ Share on other sites More sharing options...
br549 Posted March 31, 2020 Share Posted March 31, 2020 The stop light switch is located on the engine firewall left of the rear valve cover, it is mounted in a small manifold with an air line coming to it. The mack # is 1MR3544P2 or the new # is 25158791. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/61802-1998-rd688-service-brake-light-switch/#findComment-447360 Share on other sites More sharing options...
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