# tach and speedo help



## Nstygrnhatch (Mar 15, 2007)

Hi I am new to this forum and I just picked up my first nissan hb yesterday, its a 87 2wd with a z24i in it. I am very familiar with nissan but nothing this far back. lol. I brought the truck home last night and noticed the tach and the speedo both dont work, all the other gauges work fine, and the cluster lights up, anyone been down this road before? I need some tech advice. Or at least somewhere to start looking. Thanks


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## bkea (Feb 4, 2005)

Sounds like the gauge cluster may have something wrong in it. But, I'm pretty sure the speedo is cable driven and the tach is electric. Not sure why both would go out at the same time. You may be suffering from DPO (Dumb or damned previous owner) disease.


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## smj999smj (Jan 1, 2006)

I would think that they are most likely two seperate problems and would treat them as such until proven otherwise.

For the tachometer, I believe you'll find a four wire connector at the back of the cluster, two of the wires being black (B), one white (W) and one white w/ a black tracer (W/B).

The black wires are ground circuits that splice with the ground circuits of the other cluster gauges and go to body grounds. Just check the two pins in the connector for good grounds using an ohmmeter, making sure there is no excessive resistance. Since the other gauges are working, it's probably not the problem.

The W/B wire runs power from the fuse box to the cluster and you should see battery voltage at the W/B wire of the connector with the ignition in the "on" position.

The W wire is the signal wire for the tach. This wire goes through the SMJ (Super multiple junction) connector, through a joint connector, to a 2.2k ohm resistor. The wire changes to a blue colored wire coming out of the resistor and goes to the four pin connector at the ignition coil. Probably the best thing to do would be to locate the resistor, would should be not far from the coil. Check for continuity between the coil and resistor on the blue wire; there should be no excessive resistance between the two ( less than .003 ohm). You can check the resistor; should be approx. 2.2k ohm. Check the W wire from the resistor to the cluster connector; should be minimal resisitance and good contiuity. 

If all of the above check out, you have a bad tachometer.
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The speedometer is cable driven. More often than not, the cable drive breaks. Remove the cable from the pinion at the trans and you can attach a drill to turn the cable and see if the speedometer works (you may want to do this before removing the cluster to address the tach issue). If the speedometer doesn't work, you'll have to pull the cluster and observe the other end of the cable. Either the cable is broken or the speedo head. If the speedo does operate when you use the drill to turn the cable, pull the pinion assy. from the trans and inspect the gear. Sometimes the plastic gear teeth will "apple core" and no longer allow the cable to turn.


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## Nstygrnhatch (Mar 15, 2007)

thank you for all your help and knowledge, when I get a chance to break away from working on everyone elses stuff (im a mechanic) I will check all that out. I would search for the problem myself, but since its probably a common problem, I wanted to see what you guys had to say about it. Thanks a bunch.


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