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No speedo

2

2 old for this

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Mar 12, 2018
I am in the process of swapping everything from a 88 740 into a 87 740. Both cars have antilock brakes. 88 used the signal converter. None on the 87. All wire diagrams show the converter. I think the diagrams are incorrect. Speedo has power. Speedometer is inop.
 
2 old for this said:
I am in the process of swapping everything from a 88 740 into a 87 740. Both cars have antilock brakes. 88 used the signal converter. None on the 87. All wire diagrams show the converter. I think the diagrams are incorrect. Speedo has power. Speedometer is inop.
Click to expand...
Please define "everything".
Engine? Horn buttons? License light? Bunch of ABBA cassettes from the glove box?

Does the Odo work?
It gets its signal from the diff sensor, like the speedo.
How's the diff sensor and its wiring?

And so on, and so on........

<br><br><br><br><br><br><br><br><br><br><br><br>


abba.jpg


:neener:
 
A common location for loss of signal is where the speedo sensor wires come through from inside the car then drop down to the diff. The grommet where it passes through the sheet metal is the spot. The wiring breaks right there from the movement of the axle over the years.
 
MasterBlaster said:
Please define "everything".
Engine? Horn buttons? License light? Bunch of ABBA cassettes from the glove box?

Does the Odo work?
It gets its signal from the diff sensor, like the speedo.
How's the diff sensor and its wiring?

And so on, and so on........

<br><br><br><br><br><br><br><br><br><br><br><br>


abba.jpg


:neener:
Click to expand...
Swapping everything including the original air in the tires. There is continuity all the way up to abs controller. No odo
 
I think in my abs 240 the signal goes to the speedo first. If it goes to the abs first then to the speed on the 700 series. I'd check for a signal from the abs to the speedo. A scope would really be helpful but a voltmeter with a fast sample rate would let you detect the signal as well. Did you have the cluster out? Maybe just a bad connection on the back of the cluster for the speedo? Or no power to the speedo?
 
Thanks for the info. Everything was transferred from a crashed 760 into a 740. Engine trans rear axel every inch of wiring. Speedo has power but no speedo signal. Both cars have abs and it works. Found the signal converter. Must be going blind? On with the hunt.
 
On the 7-9 series the wiring from the speed sensor goes to both the speedometer and the ABS computer. It splits at the large white connector underneath the edge of the dash on the driver’s side. The connectors are tied up under the dash with a rubber covered metal strip.
 
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Got the fuel leak taken care of so back to the speedo. I took the twisted harness from the 88 and rigged it in. Speedo works but I think it is reading to fast. So that tells me the diff sensor is ok.
 
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