Okay, what the heck is this thing?

[grannyknot]

1977 280z      It lives in the dash between the Tach and Speedo, I can't find anything on the schematic with same colour wires.

 

[zKars]

It a speed sensor I'm pretty sure. Either the ignition or ECM use it for some 'critical' function. 

Something on the speedo hooks up to it. I've seen them attached to speedo's

Edited September 26, 2018 by zKars

[Dave WM]

looks like part of the BCDD system, used to know when going over 10 mph. "amplifier"

Edited September 26, 2018 by Dave WM

[AZDatsun]

It’s nothing that is on my 78


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[AZDatsun]

Oh shoot that’s the door chime I forgot about that part


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[AZDatsun]

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F152460061717


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[Captain Obvious]

Strike one:

2 hours ago, zKars said:

It a speed sensor

Strike two:

2 hours ago, Dave WM said:

looks like part of the BCDD system

Third pitch... fouled off

34 minutes ago, ryanotown22 said:

It’s nothing that is on my 78

Base hit!!

26 minutes ago, ryanotown22 said:

that’s the door chime

Haha!! Yes, it's the annoying buzzer/beeper.

Supposed to make noise when a) the key is first turned to the "ON" position (beeps six times or so and then stops),
and b) anytime the key is in the ignition and the driver's door is open

[grannyknot]

2 hours ago, zKars said:

It a speed sensor I'm pretty sure. Either the ignition or ECM use it for some 'critical' function. 

Something on the speedo hooks up to it. I've seen them attached to speedo's

Here is the speed sensor attached to the back of the Speedo,

22 minutes ago, ryanotown22 said:

Oh shoot that’s the door chime I forgot about that part


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That would make sense as one of the contacts had been disconnected but here is the diagram from the schematic which is suppose to be very accurate.

[AZDatsun]

Hey I won... also it’s page BE-79 in the 78 FSM



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[Captain Obvious]

10 minutes ago, ryanotown22 said:

Hey I won... also it’s page BE-79 in the 78 FSM

Winner!! 

 

[Captain Obvious]

Nissan wasn't very good at labeling the wire colors on the device side for many of the small devices like this. In other words... I wouldn't be surprised to find that the wire colors on the harness side are correct on the diagram, and they were just never identified on the device side. I would guess that the creator @wal280z of that colored wiring diagram probably just assumed the wire colors did NOT change since there wasn't any info to the contrary.

So... Is there a three position connector hanging down between the tach and speedo that has black/yellow, green, and black? If so, that's where that buzzer plugs in, despite the color change to a pair of reds and a black.

46 minutes ago, grannyknot said:

here is the diagram from the schematic which is suppose to be very accurate.

 

[wal280z]

On 9/26/2018 at 10:26 PM, Captain Obvious said:

Nissan wasn't very good at labeling the wire colors on the device side for many of the small devices like this. In other words... I wouldn't be surprised to find that the wire colors on the harness side are correct on the diagram, and they were just never identified on the device side. I would guess that the creator @wal280z of that colored wiring diagram probably just assumed the wire colors did NOT change since there wasn't any info to the contrary.

So... Is there a three position connector hanging down between the tach and speedo that has black/yellow, green, and black? If so, that's where that buzzer plugs in, despite the color change to a pair of reds and a black.

 

@Captain Obvious - you are correct, I did not change the wire colors from the harness to the device side - I suppose that the BE section may indicate proper wire colors on the device, but that would be another large hurdle, but it could be done.

The ONE thing that I did add to the diagram that was not on the original from Nissan was the dashed line indicating the firewall, so users could find the devices easier.