87 Ranger Tachometer Wiring

[Terry]

Do you have a dwell meter?

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[gtarplaya2k]

I don't but I can most likely borrow one this weekend

 

[gtarplaya2k]

Well turns out I cannot get a dwell meter but if hooking up the green wire allows the truck to run wouldn't it be safe to say its doing what its supposed to? What else can I try or am I stuck without a dwell meter

 

[Terry]

I would agree that wire should tell you that it is working. What about the black wire? There are only two wires that actually run the tach. Does everything else on the cluster work?

 

[gtarplaya2k]

Yes the black and I believe yellow wire next to the green and yellow wire is grounded and yes everything else works on both the clusters I have just not the tach but I find it hard to believe both clusters have bad tachs is there anyway to test

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[gtarplaya2k]

So I grounded the 3 pin and put 12v to the 4 pin assuming that should pin the tach at 7000 but nothing

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[Terry]

I know that this sounds strange but did you trace the the strips that go to the connector?

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[gtarplaya2k]

Yes the Gran/yel wire goes to the 4 pin and the black goes to 3 pin

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[gtarplaya2k]

I put power straight to the strip on the cluster and nothing

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[Spott]

I believe the tach looks for pulses (voltage spikes), coming at the speed of the engine. It won't respond to the application of 12VDC, as that is merely a single "pulse".

This is also why you couldn't get a good measurement with a digital multi-meter. An analog meter would have shown you some kind of average of the waveform.