3406B jake brakes

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by mile marker 27, Jul 29, 2022.

  1. mile marker 27

    mile marker 27 Road Train Member

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    Do most 3406B models, with jakes, have a 2 or 3 stage jake control switch? I ask because my ‘87 Pete with 4MG has, “on/off” and a switch that either up or down. When jakes are “on”, the switch beside doesn’t seem to change, whether it’s, “up” or “down”. Jakes are working but,........on which setting is the question.
     
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  3. Last Call

    Last Call Road Train Member

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    B's only have a 2 stage brake .. Hi & low...usually when the switch is in the down postion it's on low when it's in the upper postion it's usually Hi.... but it depends on if some tard has been in there with wire cutters and scotch locks ... then it's a crap shoot..
     
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  4. mile marker 27

    mile marker 27 Road Train Member

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    I guess I ought to check the wires at the spade terminals on each jake housing for voltage. Does it need to be running, or just key “on”, with Jake switch on?
    If I’m getting voltage to each spade, should I be able to hear each jake solenoid click? Could have a bad solenoid, perhaps. The jakes are working but I’m assuming they’re only working on “Low“.
     
  5. Last Call

    Last Call Road Train Member

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    The key & the switch should only need to be on to have power at the spades for the solenoids
    Iam going off of memory but I think your low should be the front 3 cylinders and Hi obviously all 6 cylinders... you can run a ohms test on your solenoids to see if they are faulty
    My experience over the years has been more switch issues or wiring issues than solenoids problems
    With out being there to see your set up.. I'am ONLY guessing but I would check for power at the solenoids 1st if you have power on three only and with the switch thrown in each postion then I would tend to think there's a issue in the switch .. or possibly the wire harness.. my bet is a switch issue..
    Again that is just my assumption from what you have posted..
    Keep us updated on what you find.. I do my best to help you
     
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  6. kranky1

    kranky1 Road Train Member

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    Check the pass thru’s on the Jake spacer.
     
  7. Last Call

    Last Call Road Train Member

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    That's good idea
    The only reason I posted some of the things I said is the way I read his post he has Low but not hi..
    This goes goes back to the old saying ..Give the laziest man the hardest job .. and he will find the easiest way to do it.....lol.. I'am lazy.. that why I really only work on my own junk
    I 'am going to assume most everything in front of the firewall is PORBABLY in working order
    BUT ... you have to start your diagnostics some where as long as your there checking for power on your solenoids right you are you should check the pass through too..
    I'am going off what he said is correct he has 3 but not 6 working .. Iam gona cut corners and jump to the Hi/Low switch .. but that just me.. I know cutting corner can easily come back to bite you in the arse..

    Now all that said @kranky1 .. I kinda aways wanted to pilot a B train .. did I pass the interview ???.. .. I just want drive .. not wrench .. you go room for a losser like me ?
     
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  8. mile marker 27

    mile marker 27 Road Train Member

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    A2C655E6-DC71-4F5B-9190-0F3CF20ABA41.jpeg I checked and appears the switch is my limiting factor. The switch, as pictured is how it’s mounted and in the “off” position. The top spade is “power” the right side spade is “low” and left is “high”. When I tested the voltage at the spade terminals, at the Jakes, the rear set was clicking and the front set had no power.
     

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  9. mile marker 27

    mile marker 27 Road Train Member

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    17438E0A-351C-4BFF-A5CC-5CC4BE55B981.jpeg
     
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  10. Last Call

    Last Call Road Train Member

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    So basically the low side of the switch is bad.. pretty easy fix .. get a new switch .. I'am always curious to make sure I diagnosed the problem correctly.. so I would run a jumper wire from the power wire to the low side wire on the switch then check my front three solenoids for power to make it was just the switch and also to make sure I have power on the front 3 so as not to have any more surprises after I install the new switch
     
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  11. mile marker 27

    mile marker 27 Road Train Member

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    I did that and the solenoid for the front 3 is clicking. So, faulty switch.
     
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