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Discussion Starter · #1 ·
Recently my tachometer has been about 500 rpms low... Like at idle it rests on the peg. But at 60mph in 5th its only about 250 off, reading just below 3k.

i replaced the ignitor, cap, and rotor within the past year or so... I mean its not that big of a deal, but just annoying, any ideas why it would do that?
 

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Doesn't your tach need four pulses to count one revolution?, and in the tach assembly there are 4 coils for this..... one could be faulty and not reading the pulse. Just a guess
 

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Discussion Starter · #3 ·
akirarex said:
Doesn't your tach need four pulses to count one revolution?, and in the tach assembly there are 4 coils for this..... one could be faulty and not reading the pulse. Just a guess
so.... how would i go about checking to see if they're faulty?
 

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akirarex said:
in the tach assembly there are 4 coils for this.
Did you just make that up?
The VSS outputs 4 pulses per revolution of the speedo cable. The tachometer reads 1 rpm per every 2 pulses per minute... For example, 2000 pulses per minute would indicate 1000 rpm.
My guess would be that the tachometer is simply wearing out. They're fairly easy to swap from any '88-91 Civic (the ones that have a tach anyway) or CRX.
 

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I was under the impression that the tach received an electrical signal from the distributor, and that only the speedometer receives input from the speedo cable. :?:
 

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You are totally right Bobski, I completely was thinking the wrong thing.
 

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GetCaughtDead said:
I was under the impression that the tach received an electrical signal from the distributor, and that only the speedometer receives input from the speedo cable. :?:
Right... I was just comparing the two, trying to understand akira's line of thought. The speedo and VSS are driven by the speedometer cable (unless you have an SiR), while the tachometer is purely electrical, operating off a signal from the ignitor unit in the distributor.
 

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Bobski, doesn't the speedo have 4 coils in the gauge itself? I know I have seen 4 coils recently on a car for the speedo. Not that the speedo has anything to do with the tach. Now if the tach needle coil was shorted in small sections that would also make it read lower than normal, right?.
 
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