AdamNS Posted March 10, 2015 Share Posted March 10, 2015 I have a 2000 Mack RD688S , all the lights work except my high beams will not come on. I have traced the wiring all looks good. Checked the fuses all looks good. checked the bulbs all good. I checked the switch on the column evrything seems ok. Anyone have any ideas where to go next? Quote Link to comment Share on other sites More sharing options...
farmer52 Posted March 10, 2015 Share Posted March 10, 2015 Not familiar with a RD...is the dimmer switch on the floor? Quote Ken PRR Country and Charter member of the "Mack Pack" Link to comment Share on other sites More sharing options...
Popular Post hatcity Posted March 11, 2015 Popular Post Share Posted March 11, 2015 seems to be working fine 3 Quote Success is only a stones throw away.................................................................for a Palestinian Link to comment Share on other sites More sharing options...
AdamNS Posted March 11, 2015 Author Share Posted March 11, 2015 No the dimmer switch in on the end of the signal stat. Quote Link to comment Share on other sites More sharing options...
j hancock Posted March 11, 2015 Share Posted March 11, 2015 At this point, time to get the test light out to see where you have power and where you don't. First stop would be the switch to make sure you have power going to the high beams. Quote JimIt doesn't cost anything to pay attention. Link to comment Share on other sites More sharing options...
turckster Posted March 11, 2015 Share Posted March 11, 2015 Check the dimmer switch on the floor. Quote Link to comment Share on other sites More sharing options...
Anne Bocchini Kirsch Posted March 16, 2015 Share Posted March 16, 2015 I agree - get a test light, start at one end and work your way toward the other. Since you say that neither light works, that would be switch to split or split to switch. Checking wiring by eye can be really tough since a lot of it is wrapped. Sometimes you get lucky and the burn is obvious, sometimes it's a tiny nick under a bunch of split loom, but if you have power both to and from your high beam switch, it's got to be something between there and where the power divides to go to each light. Quote Link to comment Share on other sites More sharing options...
MackTech Posted March 22, 2015 Share Posted March 22, 2015 Do you have fog lights? If so you may have a relay issue. Quote Link to comment Share on other sites More sharing options...
superdog405 Posted March 22, 2015 Share Posted March 22, 2015 Good place to check is up next to rad. on driver side. Your wiring runs out to hood there, should be a couple of factory plugs there. Wires rub on frame in this area, havent had an RD in a few but both my CL's have had issue in that area. Quote Link to comment Share on other sites More sharing options...
MackTech Posted March 22, 2015 Share Posted March 22, 2015 Another place is where the light assemblies are bolted to the hood sometimes wires get pinched there and short out. Quote Link to comment Share on other sites More sharing options...
felicello122 Posted March 22, 2015 Share Posted March 22, 2015 Could simply be just your dimmer /turn switch Quote Link to comment Share on other sites More sharing options...
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