3 knobs on the dash?
#11
02-23-2008, 12:48 AM
It just dawned on me...
Some of the older trucks that were constantly used to haul HAZMAT also had a PANIC BUTTON that worked with the QUAALCOM in case of a hijacking. Push it and in a few minutes, you were supposed to have all kinds of help coming.
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#12
02-23-2008, 01:40 AM
Originally Posted by Windwalker
Originally Posted by line_transporter
The yellow one controls brakes on all axles, the red is only for trailer, and the blue is only for the truck unit. It actually helps to have that blue one, because in winter time you'd want to have the trailer brakes released so that the residue water doesnt freeze in the air lines.
How long you been driving, Bud??? go up and read the sticker, it clearly says the yellow button sets the tractor spring brakes and the trailer emergency brakes.. The yellow one only sets the tractor brakes. A really good idea in winter so that you leave the trailer brakes released and don't have to use a hammer on the shoes to release the trailer brakes before you can move. I've seen guys pull into a fuel island, when the weather conditions are right, and after they fueled up, they had to have a service truck come and warm up the trailer brake drums so they could leave the fuel island. It can save you money and grief to pop the yellow one only, and leave the red one in so the brakes don't freeze to the drums. Now, I don't know about the newer tractors, but on some of the older ones, when you set the tractor brakes, you only set them on one axle. If you wanted to have both axles holding you, you also had to lock the differentials. The new ones may be different, but some of the old ones only had one set of "SPRING BRAKES" on one drive axle. If they froze to the drums, it was a lot easier to get them to breake loose than the trailer. Another good winter tip... Get a bottle of "AIR-LINE ANTI-FREEZE" and put a shot glass of it into the red glad-hand anytime the weather gets below freezing. It tends to keep the air moving in the trailer where you need it. Otherwise, you can find that the trailer brakes will not release because of ice blocking an air line. Now the BLUE BUTTON on some of the "ANCIENT" trucks had to do with an earlier form of ABS from back in the late '70s (If I remember right). The ones that when the state trooper would aim his radar at you, the brakes either didn't work at all, or they would lock up and if you were lucky, you had enough time to get it onto the shoulder before you stopped moving. They were a ROAD HAZARD!!!!!
#13
02-23-2008, 02:17 AM
Nothing to do with ABS and predates it by quite a long time. The blue button was created when the maxis were invented and before they started placing them on trailers. The blue button wont release the brakes back there. This was also on buses for a long time (maybe still is?) If you lost air out of the primary tanks in a place that was less that safe, you could push and hold the blue button and it would release the spring brakes until you release the button and or you ran that system out of air. These things are so rare (mainly because they wont really work unless bobtailing) that the only places your really going to come across them is in CDL manuals to confuse people! LOL!!!
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#14
02-23-2008, 02:32 AM
Originally Posted by Fozzy
Nothing to do with ABS and predates it by quite a long time. The blue button was created when the maxis were invented and before they started placing them on trailers. The blue button wont release the brakes back there. This was also on buses for a long time (maybe still is?) If you lost air out of the primary tanks in a place that was less that safe, you could push and hold the blue button and it would release the spring brakes until you release the button and or you ran that system out of air. These things are so rare (mainly because they wont really work unless bobtailing) that the only places your really going to come across them is in CDL manuals to OR TRUCKER MESSAGE BOARDS confuse people! LOL!!!
#15
02-23-2008, 03:21 AM
I guess that scan of the Mack manual shown in the earlier post (which explains it all quite clearly) must be B.S. too then.
My bad. :roll:
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#16
02-23-2008, 03:46 AM
Originally Posted by Rev.Vassago
Originally Posted by line_transporter
On the subject of brakes ... does anyone know what the trailer brake handle, inside the cab, is for? I only used it to check the trailer brakes before I get going, but I dont use it while driving, because it might lock the trailer axles and cause a skid.
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#17
02-23-2008, 04:21 AM
Originally Posted by Mackman
Originally Posted by Rev.Vassago
Originally Posted by line_transporter
On the subject of brakes ... does anyone know what the trailer brake handle, inside the cab, is for? I only used it to check the trailer brakes before I get going, but I dont use it while driving, because it might lock the trailer axles and cause a skid.
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#18
02-23-2008, 09:01 AM
Originally Posted by Fozzy
Originally Posted by Mackman
Originally Posted by Rev.Vassago
Originally Posted by line_transporter
On the subject of brakes ... does anyone know what the trailer brake handle, inside the cab, is for? I only used it to check the trailer brakes before I get going, but I dont use it while driving, because it might lock the trailer axles and cause a skid.
I use it when sliding tandems. Unless I have an "air-release" on the pins for the trailer tandems, I will pull the handle, then get the truck moving slow and pull the Johnny-bar. It's a LOT easier on the clutch and drive train.
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#19
02-23-2008, 09:17 AM
Simple, the "idle away" factor for the electronic engines means that you do not have to apply fuel to get the truck moving, you simply release the clutch until the engine starts to "load" remove your foot from the brake as you come of the clutch and you are away without rolling back or having to stress the heck out of anything. This was impossible for the old trucks, even on a level grade, you had to apply fuel to keep it from stalling. It is a tough habit to break. The hand valve is nice to have to slide tandems and such, but again the possibility for abuse means that those who CAN use them correctly are not able because there are too many doomuses out there.
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#20
02-23-2008, 09:18 AM
...you can use that trailer brake handle to straighten yourself out if you start sliding out of control sideways on ice down a hill, give it a slight tug and put a little power to your drives, it will straighten you out, still in a fix but straighter...
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