excavator Posted April 3, 2016 Share Posted April 3, 2016 Hi guys I just picked up another old Mack a 1986 RD tandem dump. It has the 3 round style vent holes in air heater box and a single rocker switch in middle that was not hooked up to wires in rear of box. When I try plugging in wires I can get the ac to work but I also see the center cab vent outside of cab opens and I am trying to figure out how or why it opens and if it should. The outside vent on old r model has manual knob to crank open. This one has air line to it with electric switch also Quote Link to comment Share on other sites More sharing options...
ekennedy21 Posted April 3, 2016 Share Posted April 3, 2016 I believe it should open on regular Ac but not on max Ac. And yes its automatic not manual. 1 Quote Link to comment Share on other sites More sharing options...
excavator Posted April 3, 2016 Author Share Posted April 3, 2016 Hey thanks. The rocker switch is only 2 position and might be the wrong one. Does anyone know if it has 3 position as heat max ac and ac Quote Link to comment Share on other sites More sharing options...
ekennedy21 Posted April 3, 2016 Share Posted April 3, 2016 if it is the older heat/ac unit it may only have 1 a/c, i am not sure. Quote Link to comment Share on other sites More sharing options...
excavator Posted April 3, 2016 Author Share Posted April 3, 2016 Ok thanks. I can get ac to work but I just don't know if it is right way. May not matter much as long as it works Quote Link to comment Share on other sites More sharing options...
ekennedy21 Posted April 3, 2016 Share Posted April 3, 2016 I just thought that the older heat/ ac unit had a couple rotary switches, not a rocker switch. maybe it is the wrong switch. Quote Link to comment Share on other sites More sharing options...
85snowdog Posted April 3, 2016 Share Posted April 3, 2016 5 hours ago, excavator said: Hey thanks. The rocker switch is only 2 position and might be the wrong one. Does anyone know if it has 3 position as heat max ac and ac Yes it should have 3 positions . Just like ekennedy21 said, the vent should open on heat and a/c but should be closed for max a/c 1 Quote Keith Link to comment Share on other sites More sharing options...
excavator Posted April 3, 2016 Author Share Posted April 3, 2016 Hey thanks for pic Mine looks just like the pic however the switch that was in there was not hooked up and is only 2 position. I will get a 3 position and see how that does. Do you know how many wires plug into 3 position switch in that pic Quote Link to comment Share on other sites More sharing options...
Emkat817 Posted August 13, 2021 Share Posted August 13, 2021 I have an 86 r model Mack and the a/c turns on but the cable connected to the switch that moves left to right to have air blow out front vents is broken!! The switch will not move. The cable runs back into metal box I can’t even stick my hand back to.. what is this cable called and where does it go? Not sure how to get back to it without tearing the whole dash apart Quote Link to comment Share on other sites More sharing options...
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