ThaddeusW Posted February 28, 2006 Share Posted February 28, 2006 Hey guys I cant seem to find out what the third blue knob on the dashboard does. Yellow is parking for the truck/tractor and red is trailer air supply. What does the blue one do? Quote -Thad What America needs is less bull and more Bulldog! Link to comment https://www.bigmacktrucks.com/topic/876-blue-knob-on-dash-for-parking/ Share on other sites More sharing options...
Lmackattack Posted February 28, 2006 Share Posted February 28, 2006 blue is tractor parkyellow is tractor and trailer parkred is trailer park Quote Link to comment https://www.bigmacktrucks.com/topic/876-blue-knob-on-dash-for-parking/#findComment-4459 Share on other sites More sharing options...
ThaddeusW Posted February 28, 2006 Author Share Posted February 28, 2006 blue is tractor parkyellow is tractor and trailer parkred is trailer parkWhen you pull the yellow knob out does the red one automatically pop out? Quote -Thad What America needs is less bull and more Bulldog! Link to comment https://www.bigmacktrucks.com/topic/876-blue-knob-on-dash-for-parking/#findComment-4460 Share on other sites More sharing options...
Lmackattack Posted February 28, 2006 Share Posted February 28, 2006 if you are hooked to a trailer and pull the yellow one I think the red pops out also. when the blue is pulled the yellow and red stay in.. I move the truck every day and never stop to think about it but I think thats how mine works Quote Link to comment https://www.bigmacktrucks.com/topic/876-blue-knob-on-dash-for-parking/#findComment-4462 Share on other sites More sharing options...
Superdog1986 Posted March 1, 2006 Share Posted March 1, 2006 ya trent when you pull the yellow the red pops out too the blue is sperate and doesnt pop out automatically when the other 2 are pulled. Quote Link to comment https://www.bigmacktrucks.com/topic/876-blue-knob-on-dash-for-parking/#findComment-4470 Share on other sites More sharing options...
ThaddeusW Posted March 1, 2006 Author Share Posted March 1, 2006 Thanks guys!I was looking at some air brake diagrams and at the function of the trailer valve on the bendix site. When you push the yellow knob in you not only supply air to the spring brakes but also send air to the control port on the trailer valve. Without the control signal the trailer valve pops out. The blue knob is downstream the park valve and trailer valve. It lets you park the tractor while keeping the control port on the trailer valve supplied allowing you to keep the trailer charged. Here is a little diagram I pulled from a bendix diagram. I labeld and colored the valves according to the dash knob color. Quote -Thad What America needs is less bull and more Bulldog! Link to comment https://www.bigmacktrucks.com/topic/876-blue-knob-on-dash-for-parking/#findComment-4473 Share on other sites More sharing options...
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