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Thread: Re-install dashboard

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    Registered User chuys's Avatar
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    Default Re-install dashboard

    Hi,

    I'm new to this forum and this is my first post. My car is a 1976 280Z 2+2.

    I have removed the dashboard of my car to work on the hoses in the AC system and re-upholster the top foam.

    After re-installing the dashboard I have 2 problems:
    1. Headlights won't turn on. All other lights do.
    2. The brake light in the Speedometer is on and the brakes are way too low.


    I have reviewed the switches and the fusible links and they are all Ok.

    Any ideas on what could be wrong?

    Thanks,

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    First guess is that you don't have something plugged back in properly. Look at the BE section of the 76 FSM. It gives breakouts of the different circuits, including the headlight circuit. It gives you a pretty good idea of how to trace the circuit.

    Do you have a multimeter, and do you know how to use it? If so, I can give you better diagnostics.
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    Hi SteveJ, thanks for the reply. I have the FSM and a multimeter too.

    I was reading on some other posts that the switch in the steering column might be at fault but I checked it and it seems to be Ok. Also, the stereo is not powering up either.

    When dismounting the dashboard I made the mistake of not unplugging the battery. Besides fuses, what else might have got broken?

    Thanks again.

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    Quote Originally Posted by chuys View Post
    When dismounting the dashboard I made the mistake of not unplugging the battery. Besides fuses, what else might have got broken?
    Yikes! That's bad mojo. Do you have an ammeter or voltmeter? I believe you might have the ammeter. If so, you could have damaged that. Are you sure you made all of the connections properly when putting the dash back in?
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    Registered User chuys's Avatar
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    On my gauges? I have voltmeter... it works. All of the gauges work.

    I'm pretty sure I plugged everything back in correctly. I labeled the wires with tape with the exception of the wires near the brake pedal; I tried both ways with no difference.

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    So far I have been able to trace power all the way to connector C7 (smaller black connector leading to the engine room). From battery -> fusible links -> combo switch -> fuse box -> harness box. I am about to test the actual leads on the headlamps themselves but I don't suspect fault.

    What I found is that if I check for continuity between the headlamp fusible link and the head-cover in the engine, there is continuity. If I'm reading it correctly, somewhere in the headlight circuit there is a mixup of ground/current.

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    I'm back after some testing... I know this sounds like a lame excuse but it's not. I have checked inside connections according to FSM and they all work (wires, fuses, connectors, switches).

    What I found is that the 3 wires going to the headlamp are crossed somewhere inside the engine room. RW, RB, R all have continuity to the RW cable in the brown connector (harness box); they also have continuity to the black cable in the harness box brown connector.

    I'm thinking of going into the wire set, right before they split, and make some direct connections.

    Thoughts?

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    sounds like a loose ground connection. check all grounds.

    Sure am glad you replaced the hoses......My 76 2+2 got to where the heater wouldn't work....and it ended up being a dry rotted hose!

    ~Joe

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    I went it and put a direct ground in the RB wire while R and RW registered current and the headlamp didn't come on. Now I'm all confused. Isn't that the way it's supposed to be? 2 currents (RW, R) and one ground (RB)?

    Please help.

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    Quote Originally Posted by chuys View Post
    I'm thinking of going into the wire set, right before they split, and make some direct connections.

    Thoughts?
    Why would things change in the harness? Did they work before you removed the dash? Odds of something wrong in the harness are low.

    You can learn a lot sitting in the driver's seat with the cover off of the switches on the steering column and voltmeter in hand. Power comes in to the combo switch there from the fusible link, heads down to the fuse box, where it splits to left and right HL's (fuses), then comes back to the dimmer switch in the turn signal stalk. You can check power in to and out of the headlight switch from the top of the switch. The solder joints are exposed. You can probably unplug the dimmer switch and ground the head lights with a jumper to see if the dimmer switch is the problem. Or check for voltage at the dimmer switch plug. Check, check, turn light switch on, check.

    Don't forget the simple possibility of bad headlights also.
    1976 280Z, with some minor modifications

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    I'll describe the circuit in detail.

    There is a WR wire going to the headlight switch (12VDC+). When the switch is on, power comes out a R wire and goes to the fuse box. There is splits between the two headlights, coming out R (right) and RY (left). The R & RY wires go to their respective headlights. There are RB (low) and RW (high) wires coming out of the headlights. Those wires go back to the dimmer switch. The switch connects RB to ground in one position for low beams, and it connects RW to ground for high beams.

    Be careful about running random wires to components. You'll be replacing a lot more wiring, especially if you bypass a fuse and burn up the wiring. Even worse, you could cause an electrical fire and lose the car or possibly the garage/house.
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    Quote Originally Posted by SteveJ View Post
    I'll describe the circuit in detail.

    There is a WR wire going to the headlight switch (12VDC+). When the switch is on, power comes out a R wire and goes to the fuse box. There is splits between the two headlights, coming out R (right) and RY (left). The R & RY wires go to their respective headlights. There are RB (low) and RW (high) wires coming out of the headlights. Those wires go back to the dimmer switch. The switch connects RB to ground in one position for low beams, and it connects RW to ground for high beams.
    Just to clarify Steve's comment, the combo/light switch switches GROUND and not POWER. As Steve pointed out, all the Red wires (R/W, R, , R/Y, and R/B) would be considered "power" wires. The light switch simply selects which wire should receive the ground, either R/W or R/B. The R and R/Y wires run out to the headlights and provides power to both the R/W and R/B wires at the same time, however, until one of them (R/W or R/B) is grounded the lights will not turn on.
    -Bo

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    Quote Originally Posted by ktm View Post
    Just to clarify Steve's comment, the combo/light switch switches GROUND and not POWER. As Steve pointed out, all the Red wires (R/W, R, , R/Y, and R/B) would be considered "power" wires. The light switch simply selects which wire should receive the ground, either R/W or R/B. The R and R/Y wires run out to the headlights and provides power to both the R/W and R/B wires at the same time, however, until one of them (R/W or R/B) is grounded the lights will not turn on.
    Actually the combo switch on his car does control the connection from between the WR & R wires, so it does switch the power. The dimmer switch completes the ground.
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    Thank you all for your input. I have checked the right lamp and all 3 wires get power at the very end of the connector. As far as I can tell, the lamp itself is Ok (filaments still in place).

    The problem, I believe, is that when checking continuity between these 3 wires and the ground connection in C7 (black wire) the multi-meter beeps, which leads me to believe that somewhere in the circuit ground and current are mixed.

    I'm about to create a new harness with relays and be over with the original harness. I did the same for the stereo and it worked.

    Wish me luck.
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