Bill 88 R 688 ST Posted September 6, 2023 Share Posted September 6, 2023 Hello all, Looking for some advice. On my 1988 R688ST I have no high beams when I push the floor dimmer switch. Headlights just go out, low beams work fine. Pulled a bulb and tested on a different truck just to confirm that it wasn't that somehow miraculously both high beams failed at the exact same time... Could this just be a bad floor dimmer switch, or should I be looking elsewhere? Quote Link to comment https://www.bigmacktrucks.com/topic/73264-r-model-high-beam-issue/ Share on other sites More sharing options...
tjc transport Posted September 6, 2023 Share Posted September 6, 2023 unplug the switch and inspect the plug and contacts for corrosion. than with a jumper wire go from center terminal to each side. center should be hot, and the sides should be low and high. this test will check the wiring. but yes, i would replace the switch because that is the weak part of the system. sometimes you need to replace the switch and pigtail too. 2 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/73264-r-model-high-beam-issue/#findComment-538367 Share on other sites More sharing options...
doubleclutchinweasel Posted September 6, 2023 Share Posted September 6, 2023 Do you have the toggle switch on the dash to flash the high beams? If so, do they work when that switch is flipped? IIRC, that same toggle will dim the lights if they are on high beam. I THINK that switch energizes the high beam filament without going through the "tilt beam" switch. Might help narrow it down pretty quickly to the dimmer switch. 1 1 Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment https://www.bigmacktrucks.com/topic/73264-r-model-high-beam-issue/#findComment-538376 Share on other sites More sharing options...
Bill 88 R 688 ST Posted September 6, 2023 Author Share Posted September 6, 2023 Thanks tjc transport and Doubleclutchinweasel, I do have the dash toggle, didn't even cross my mind to try that. Will give that a shot.... before just replacing the switch then do a jumper test if needed... Prefer to diagnose before firing the parts cannon, although the dimmer switch is pretty cheap ammo...😂 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73264-r-model-high-beam-issue/#findComment-538388 Share on other sites More sharing options...
Bill 88 R 688 ST Posted September 7, 2023 Author Share Posted September 7, 2023 Thanks again guys.... High beams working with dash toggle, cleaned up pigtail and switch connections and working fine with switch now...😁 She's an old dog, but a happy dog. '88 R688ST/350 4v/T-2090 Much more fun than driving the '09 vision around waiting for the cel to come on again😑🤦♂️ Plus you gotta love the black puff of power with every gear😁 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73264-r-model-high-beam-issue/#findComment-538406 Share on other sites More sharing options...
doubleclutchinweasel Posted September 7, 2023 Share Posted September 7, 2023 Thanks for coming back with the fix. That really help folks out on here. Too many people never give that feedback. Glad the Dog is happy again! 1 Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment https://www.bigmacktrucks.com/topic/73264-r-model-high-beam-issue/#findComment-538415 Share on other sites More sharing options...
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