76' Speed Sensor Issue? (1 Viewer)

Dc75nm

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Hello Everyone,

Recently my speedo & odometer stopped working. I've checked the cable from the tranny to the speed sensor and he spins as expected. I disconnected the cable between the speed sensor and the gauge cluster and he functions as expected. When this cable is connected to the speed sensor but disconnected from the gauges, it does not spin as expected. So I think my issue is at the speed sensor.

I did some poking around with my DMM on the speed sensor. I tested for power to the two pin connector and one of the wires is getting 12V; not sure what the other wire is for. The wire with the single pin connector (greed) appears to be connected to the starter and does not have any voltage on him when the ignition in the on position. Although, if I apply 12V, the starter engages.

Is there additional trouble shooting I should do before blaming all my issues on a bad speed sensor?

Thanks for reading,

Dennis
 
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Jul 16, 2013
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Montana
Speed sensor? Wires to pin connectors? I'm sure smarter people than me will chime in, but mine is an '82 and is all mechanical with the cable connection and gear at the back of the transfer case going to the back of the speedo. So sensors.
Does it have the original system? Maybe photos will help.
 
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If you're looking at the junction on the upper passenger side of the firewall, that's the EGR "maintenance interval detector"... it's got some gearing to pass the rotation of the cable through, but it's just a 1:1. There are one piece cables to eliminate it if it has issues.

Or it's a Dakota digital dash, and all bets are off then. 😄
 

Dc75nm

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Rio Rancho
Yeah. It's that little junction box you described. I have the factory gauge cluster. I didn't know it's 1:1; thanks for pointing that out. I think I'll simplify it and run a one piece cable.
 

Dc75nm

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Just want to verify, that little junction box is mechanical? At least the speedo function of it?
 
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yes I'm pretty sure it just has a second output gear or something that spins the cable connected to the gauge cluster

I deleted mine and installed a one piece cable
 
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Yeah, it's just an "odometer" inside, with a 90* gear with two outputs...one drives the speedometer, and one drives the calculator.

PXL_20210824_212153359.MP.jpg
 

Dc75nm

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Interesting. So if I pop mine open I'll find an odometer inside? Assuming it's original to the vehicle, could this be used to determine the mileage? My cruiser came with a busted odometer so as of right now, mileage is unknown.
 
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It looks like an odometer wheel, but I don't think it reflects mileage specifically. Mine had 120883 on the clock, but that maintenance box showed that 424318. It was used to trigger the EGR light on the dash at some interval, and (I think) you reset that switch under the cap after doing the service.

You might be able to do some math though - not sure. My numbers were different by a ratio of 3.5x...so maybe that same math could give you a very rough guess on your mileage. Alternatively, that device may have "rolled over" a few times itself, and then all bets are really off. 😆
 
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