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  • 3 years later...

I believe what you are looking for is printed in individual books, I assume you want all you can find,  what year is youre RW?.... 613 or 713? what tranny? and rears, probably Mack 92/93 series...  I have a lot of books (not for sale) and I can show you the book number, so you can search the Web...  jojo

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ok, the engine should be an E-6 4 valve..  The wiring diagrams are basically, R/RD/RW ..  very similar if not identical. what electrical issues is he trying to fix.? The truck is pretty simple compared to todays truck's. 

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There are a lot of smart guys on here, that can help you.  If you need to P.M. me, please do and include youre brothers phone number and mabey I can help him.. jojo

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I think that switch is on the treadle valve under the floor pan..  when the pedal is pressed, it closes the circuit and lights the brake lights.  10 PSI is enough...  you can test the circuit by unplugging the terminals and crossing them, brake lights should be lit at this time... jojo

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Jojo you have been nothing but a huge help. After replacing the brake valve there still seems to be ~35 psi at the stop light switch. The line coming to this switch comes from the tractor protection valve. Do you think the TP valve could be leaking air into the service line? is there a way to diagnose before replacing

 

Jeff 

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mabey pull a line , one at a time from the treadle valve to find which line is feeding the switch port. pul a line, if its not it, hook it back up, and go to the next one..  is the trolly brake valve defective?  im sorry but im at a bit of a loss. it would be better if I could see the issue as it happens...  jojo

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I believe the tractor protection valve would have to be charged before any air pressure could get from one side to the other the brake relay valves for the service brakes are in the system also and are suspect to leak pressure back through the service brake circuit

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Im just curious how air pressure is present at the air switch, turning the brake lights on..  I wonder if he unhooks each brake valve to find the one that is back feeding air?  what do you think, D-Day ?

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Jeff, one thing i'm still not clear on... when all the lines are hooked up, and a little air pressure is present at the switch...  have you tried to move the truck, to see if the brakes are dragging. or even just un-hook the service lines on the brake chambers to see if pressure is present? (yellow button pushed in) ?  jojo

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27 minutes ago, Joey Mack said:

Jeff, one thing i'm still not clear on... when all the lines are hooked up, and a little air pressure is present at the switch...  have you tried to move the truck, to see if the brakes are dragging. or even just un-hook the service lines on the brake chambers to see if pressure is present? (yellow button pushed in) ?  jojo

They don't seem to be dragging at all. I haven't unhooked the lines at the chambers to test this. I do intend on replacing the service chambers 

Jeff 

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26 minutes ago, D-Day said:

I have found in the past that with the park brake released (yellow button in) it usually is coming from one of the park brake chambers leaking through to the service side

D-day, what would be faulty in this scenario? the park brake chamber? allowing the air to flow through to the service side. 

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49 minutes ago, Joey Mack said:

Im just curious how air pressure is present at the air switch, turning the brake lights on..  I wonder if he unhooks each brake valve to find the one that is back feeding air?  what do you think, D-Day ?

I'll try this method and see if I can back track to what the problem is. 

Jeff 

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i feel the same as D-Day. some other valve is passing air..  I'm gonna sit back and watch...  dont want to put a wrench in the works,,, jojo

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On 1/31/2022 at 6:23 PM, Joey Mack said:

Also, check to see that the piston under the brake pedal isn't sticking, which can allow air to activate the brake light switch.  Take it apart if you can, they tend to get corroated because of what fall's off the sole's of your boot's.  try to clean the bore and emory cloth the piston, if the rubber boot is junk, replace it, coat the side of the piston with anti seize and put it back together and re-test...  jojo

Jeff,  if you haven't checked the piston under the the brake pedal like Jojo mentioned , make sure you take it apart and clean it before you start buying parts. It can just stick on a little and you would never know and seem like its ok. 

And I think it was said , but check the hand brake( trolly valve ) is not on. I have chased that before. Looking for why brake lights on and hand brake had been applied without me realizing . 

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Keith 

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15 minutes ago, 85snowdog said:

Jeff,  if you haven't checked the piston under the the brake pedal like Jojo mentioned , make sure you take it apart and clean it before you start buying parts. It can just stick on a little and you would never know and seem like its ok. 

And I think it was said , but check the hand brake( trolly valve ) is not on. I have chased that before. Looking for why brake lights on and hand brake had been applied without me realizing . 

85, we did do the first part we actually took it all apart and put a new brake valve. In the process we clean the piston and put the antiseize (it moves freely.) I am wondering if the problem is this trolley valve. We will play with this and see if the pressure changes. Thanks!

 

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