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Thread: Overdrive Wiring Check

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    Overdrive Wiring Check

    I have a BJ8p1 with an overdrive that no longer works following some major restoration work over the winter. I have two suspects at the moment, and wondered if anyone with a BJ8 could check the following:

    1) throttle switch is closed (continuity across switch) with accelerator relaxed, but the circuit opens (no continuity) when acceletrator is pushed to floor?
    2) overdrive relay (under hood on firewall, not solenoid at gearbox) - could someone please describe which wires connect to which terminals on the relay?

    thanks
    steve

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    Re: Overdrive Wiring Check

    Steve
    there are better people here than me to give advice but i will give it a shot.

    1) on the throttle switch: here is what i did. first turn off the power at the battery. next i measured the travel for the gas pedal from rest to the floor. as i understand it the switch should kick out about a 1/3 of the way to the floor. once i had the travel length, i cut a prop that rests against the seat frame and holds the gas pedal 1/3 the way down. then i disconnetced the two wires to the switch. i hooked a multi meter to the two terminals and adjusted the screw head until the switch was at the point of closing and opening. then i tightened the arm to the screw. unhook the multi meter and reattach the wires. Works for me and the kick out feels like a good spot to me.

    2) attached is a picture of a wiring diagram for a BT7 but i think the relay is the same. blow it up and you can see the wiring.
    IMG_0265.jpg

    sounds like you have nothing working. If it were me, i would flip all the switches on and put the car in 3rd or 4th gear. then turn the battery on and check for voltage at the solenoid. if nothing, go thru each switch backwards, starting at the gear lever switch. go back thru the circuit to see where the circuit is broken.

    but again there are people on here with a lot more experience than me. i am sure some will chime in here soon. good luck.

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    Luke Skywalker RAC68's Avatar
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    Re: Overdrive Wiring Check

    Hi Steve,

    I have a Neg. ground BJ8P1 and my OD has been working perfectly since new. I checked the continuity of my throttle switch, as you requested, and verified that at rest, the switch is closed and opens as the accelerator is pressed.

    Also, there are (3) double wire connectors and 1 ground connector wired as follows: C1 - White/purple, W2 - White, C2 - White/Green, W1 - Black (ground)

    Hope this helps,
    Ray(64BJ8P1)
    Last edited by RAC68; 05-16-2018 at 07:37 AM.

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    Re: Overdrive Wiring Check

    This is a great idea. I’m trying hard to not take the tunnel off (yet again !!) so want to verify that I’ve reconnected the wiring correctly first. I’ll give this a try if I don’t find a wiring fault....

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    Re: Overdrive Wiring Check

    Thanks Ray. So my throttle switch is correct. I’ll verify the wiring connections tonight.

    When the relay is energized by throwing the dash switch, does anyone know if the effect is to connect C1 and C2?

    thanks
    steve

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    Luke Skywalker RAC68's Avatar
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    Re: Overdrive Wiring Check

    Steve,

    Take a look at this article on the OD and the relay's operation (http://www.healey6.com/Technical/Tec...leshooting.pdf). You will note that the wiring in the article is different from the connections I have provided. I believe that my reversal of the W1 and W2 connections is related to my change from positive ground to negative ground. Since W1 and W2 are both ends of the actuating coil within the relay, I don't think the switch did anything with relation to the relays operation.

    To answer your question on the effect of C1 and C2, the article goes through the relays operation and its effect on the circuit. I think you will find your answer and a good understanding.

    One last point. Since the OD is not fuse protected, I installed a 10 amp in-line Fuse (in-line fuses are easily hidden) on the white wire to protect the wiring of the circuit. To help protect the Solenoid, some have pulled the cover from the trans and installed a slow-blow 20 amp fuse directly on the solenoid power line. However, if this fuse ever fails, you would have to pull the transmission to replace the fuse (which may also be necessary to find out what caused the failure). When viewing the wiring again, I will be installing an in-line slow blow 20 amp fuse on the Whit/Green (C2) branch going to the transmission switch (the W/Gr branch NOT coming from the Throttle Switch). This installation should provide some protection if the Solenoid fails to activate properly and the fuse would be accessible.

    Enjoy the pursuit of the solution and your Healey,
    Ray(64BJ8P1)
    Last edited by RAC68; 05-17-2018 at 04:37 AM.

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    Re: Overdrive Wiring Check

    Thanks Steve - really comprehensive article. I’m sure I’ll find my answers here! Much appreciated.
    steve

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    Re: Overdrive Wiring Check

    FWIW I had a similar problem and worked backwards like you - but at the end of the day that tunnel had to come off. Unless you have been fiddling with the throttle shafts and that that throttle switch the prime cause is nearly always the solenoid.

    If you have the work shop manual there is a section in there that explains all the checks.



    Bob

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    Re: Overdrive Wiring Check

    I checked the wiring to the relay and there was an error. Upon correction, I can hear the overdrive solenoid click when I flip the switch. The gear position switch is a bit flaky though, as I can hear it engage/disengage as I wiggle the shifter....

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    Re: Overdrive Wiring Check

    Steve

    That sounds normal to me. That is part of the fail safe to prevent the overdrive being operated in reverse or in 1st and 2nd



    Bob

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    Re: Overdrive Wiring Check

    steve
    my old gear shift switch was the same way. if i moved the shifter around a little it would click in and out. they are not too expensive, as i recall, so i just went ahead and put in a new one since i had to replace the dash switch. have not noticed any issues with the new one. easy also since i already had the tunnel cover off.

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    Re: Overdrive Wiring Check

    Guys

    Moving the gear stick whilst the overdrive is engaged will produce a clicking sound - the overdrive and switch are working properly. The trouble comes when you are driving along in overdrive and the chattering starts you will go in and out of overdrive. This is a sign that the switch needs changing as the push button activator on the switch has severely worn.



    Bob

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    Re: Overdrive Wiring Check

    Bob, you nailed it. The problem was with the gear selector switch - it was just slightly too far away from the base of the stick to engage the switch. Minor adjustment and all working now...

    thanks everyone.

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