1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

No Brakelights

Discussion in 'Early CJ5 and CJ6 Tech' started by Boyink, Oct 14, 2005.

Page 1 of 2
  1. Oct 14, 2005
    Boyink

    Boyink Super Moderator Staff Member

    Tulsa, OK
    Joined:
    Sep 20, 2002
    Messages:
    6,197
    OK...trying to figure this out...want to check my logic before getting greasy going after the wrong part...;)

    After we got home from the dunes I noticed that the wagon had no brakelights. I figured something in one of my new flat-towing connections had shorted the fuse out. Replaced the fuse and the wagon is fine.

    Then no brakelights on SSDutch. Dutch had more of the wiring routed through a fusepanel, so I'm new to the original wiring setup.

    I have tailights.

    I have turnsignals.

    This tells me the wiring to the lights isn't shorted to ground anywhere.

    Looking at the FSM, I see two possibilities left -- either the circuit breaker on the back of the light switch, or the brakelight switch itself.

    Since the other lights work, I figure the circuit breaker is good, which leaves only the brakelight switch.

    My FSM shows two diagrams - an "early" with only one brake light switch, and a "late" with a front and rear brake light switch. It says of the two switches that they "work independantly of each other", and I haven't a clue what that means nor where to look for a rear. I can see the wires coming off the one on the front of the master cylinder.

    So - is my logic correct, and where would that second "rear" brakelight switch be?
     
    Boyink, Oct 14, 2005
    #1
  2. Oct 14, 2005
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Logic sounds ok to me. The turn signals are the same filament and wiring, so if they work, verything from there back should be ok.

    The brake light switch is just a switch - if you connect the two leads, and the lights light, that's the problem. I assume that the switch you can see is the hydraulic type on the master cylinder?

    Don't know about front and rear.
     
    timgr, Oct 14, 2005
    #2
  3. Oct 14, 2005
    Hippo393

    Hippo393 Jeepless

    Charlotte, NC
    Joined:
    Sep 22, 2002
    Messages:
    1,130
    Hi Mike,

    I doubt your 6 has the 2nd switch. On my '71, it's inside the frame rail and can be easily seen when ya look underneath. Just follow the brake lines towards the rear and it will be visible if you have one. :beer:

    BTW logic sound good. :)
     
    Hippo393, Oct 14, 2005
    #3
  4. Oct 14, 2005
    Boyink

    Boyink Super Moderator Staff Member

    Tulsa, OK
    Joined:
    Sep 20, 2002
    Messages:
    6,197
    OK...just checked the switch on the M/C and it's good.

    Further downstream is where I tied in the flat-tow harness...but again it seems that if one of my diodes blew I'd also have lost either a turn signal or tailight.

    I should have 12V on one of those wires to the brake light switch, correct?

    And looking at the wiring diagram, the horn is the only other thing I see running through that circuit breaker (thought the turn/tail lights would be as well)....
     
    Boyink, Oct 14, 2005
    #4
  5. Oct 14, 2005
    Boyink

    Boyink Super Moderator Staff Member

    Tulsa, OK
    Joined:
    Sep 20, 2002
    Messages:
    6,197
    My horn is disconnected due to a short in the column...but if I plug it in the horn sounds...so the circuit breaker must be good as well.
     
    Boyink, Oct 14, 2005
    #5
  6. Oct 14, 2005
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Is there a circuit diagram online somewhere?
     
    timgr, Oct 14, 2005
    #6
  7. Oct 14, 2005
    Hippo393

    Hippo393 Jeepless

    Charlotte, NC
    Joined:
    Sep 22, 2002
    Messages:
    1,130
    Is that a single-resivoir MC?

    Is the MC topped off w/ brake fluid?

    Yes on the 12V.

    Just an idea...if there're any unused dummy lights on your speedo, consider adding a small wire from the brakelights' wire to the speedo cluster. The dummy light (in my case on the '71, the red "BRAKE" dummy light) lights up when I brake. I did this the last time I had the dash off, and I can't believe the peace of mind knowing that the folks behind me will see brake lights, and exactly when they turn on as I depress the pedal. :)
     
    Hippo393, Oct 14, 2005
    #7
  8. Oct 14, 2005
    blevisay

    blevisay Oh Noooooooooooooooo! Staff Member

    Portland Tn.
    Joined:
    Sep 20, 2002
    Messages:
    4,350
    Mike where did you splice the diodes in?
     
    blevisay, Oct 14, 2005
    #8
  9. Oct 14, 2005
    Boyink

    Boyink Super Moderator Staff Member

    Tulsa, OK
    Joined:
    Sep 20, 2002
    Messages:
    6,197
    Down stream of the brakelight switch, under the driver's seat.

    MC topped off, yes.

    12V to one side of the brakelight switch...gotta be downstream of that.

    Will check further...
     
    Boyink, Oct 14, 2005
    #9
  10. Oct 14, 2005
    Boyink

    Boyink Super Moderator Staff Member

    Tulsa, OK
    Joined:
    Sep 20, 2002
    Messages:
    6,197
    These are the diodes I used. Even with a bit of electronics background I couldnt make sense of the ratings....but they were the biggest RS had.
     
    Boyink, Oct 14, 2005
    #10
  11. Oct 14, 2005
    vanguard

    vanguard

    vanguard, Oct 14, 2005
    #11
  12. Oct 14, 2005
    Boyink

    Boyink Super Moderator Staff Member

    Tulsa, OK
    Joined:
    Sep 20, 2002
    Messages:
    6,197
    :shock:

    85A?

    $24?

    Musta got them on sale...and in chrome...:)
     
    Boyink, Oct 14, 2005
    #12
  13. Oct 14, 2005
    vanguard

    vanguard

    I got them locally for about $10 each. They are made for this application, while your radio shack units are undersized. Might have failed due to heat??
     
    vanguard, Oct 14, 2005
    #13
  14. Oct 14, 2005
    Boyink

    Boyink Super Moderator Staff Member

    Tulsa, OK
    Joined:
    Sep 20, 2002
    Messages:
    6,197
    Yea..I'm thinking it has to be the diode. Seems like 85A is overkill though, when taillights are normally fused at 20A.
     
    Boyink, Oct 14, 2005
    #14
  15. Oct 14, 2005
    BlueFlu

    BlueFlu past owner of some ecj5's

    Hermitage, TN
    Joined:
    Jan 21, 2004
    Messages:
    1,552
    Mike can you rig up a jumper wire real fast to test the wire?
    Bypassing the diode.
     
    BlueFlu, Oct 14, 2005
    #15
  16. Oct 14, 2005
    Boyink

    Boyink Super Moderator Staff Member

    Tulsa, OK
    Joined:
    Sep 20, 2002
    Messages:
    6,197
    Yeah...as soon as I get done with client calls, supper, etc I can get out there and check for continuity across the diode.

    Pretty sure that has to be it..I wanted bigger ones but that's all RS had. I did bench test one - hooked up spare taillight through it and let it sit for ~20 minutes with the brakelight on. I could still touch the diode at that point, so figured it would be OK....
     
    Boyink, Oct 14, 2005
    #16
  17. Oct 14, 2005
    kamel

    kamel Senior Curmudgeon

    Erlanger, Kentucky
    Joined:
    Jun 10, 2003
    Messages:
    891
    The two light switches (if you have two) should work independently unless someone has fooled with the wiring.

    That means the switches are in parallel so that either switch will make the brake lights stay on.

    They should have 12 volts on one side and the other side should go to the turn signal switch.

    Now, if you you have 12 volts on one of the terminals on the brake switch, and short circuit across the two terminals on the brake light switch and dont get stop lights then the wiring back to the turn signal switch is bad or the turn signal switch is bad.

    Since it used to work and now doesn't, I'd look for a wire that has been ripped loose.

    I believe these are brown wires.

    If someone has gotten in there and monkeyed around with the wires, it is anyone's guess what is bad, but if it worked OK and then quit after running the jeep, a broken or loose wire is what I'd expect.
     
    kamel, Oct 14, 2005
    #17
  18. Oct 14, 2005
    Old Bill

    Old Bill Aggressively passive....

    Really Southern...
    Joined:
    Nov 12, 2004
    Messages:
    822
    Yeah, but you doubled the load with 2 brakelights....

    Hope you sort it out easily.
     
    Old Bill, Oct 14, 2005
    #18
  19. Oct 14, 2005
    dohc281

    dohc281 It is what it is.

    Laurel Springs, N.J.
    Joined:
    Dec 30, 2004
    Messages:
    605
    What are the purpose of the diodes, are they taking the place of fuses?
     
    dohc281, Oct 14, 2005
    #19
  20. Oct 14, 2005
    vanguard

    vanguard

    They act as one-way electrical valves. They prevent the electrical system in the towed vehicle from flowing back into the towing vehicle.
     
    vanguard, Oct 14, 2005
    #20
Page 1 of 2
New Posts