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Discussion Starter · #1 ·
On my 1990 CRX Si my RPM guage needle shows it idles at 1100 RPM when its really 750. How can i fix that ?
 

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Discussion Starter · #3 ·
joelidge said:
How do you know the car is idling at 750 and not 1100?
Because the technician used a tachometer tool which mesures idle speed.
 

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The tach circuit is very simple. The igniter sends a signal to the tach via a single signal wire that doesn't touch anything between the two. Being you are getting a signal, it probably isn't an issue with the wire and probably not the igniter either.

I know you can calibrate some tachs. Here is a link to another thread discussing that:

https://crxcommunity.com/viewtopic.php?f=3&t=57558
 

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Robb said:
Baker said:
Robb said:
joelidge said:
How do you know the car is idling at 750 and not 1100?
Because the technician used a tachometer tool which mesures idle speed.
The technician didn't know how to remedy it?
2 techs told me I need a new cluster...
That may be what you may end up having to do then.
I'm surprised you don't have BNIB NOS Honda gauges stockpiled.
 

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It’s common for a CRX tach to drift out of calibration. I have found that cleaning up the screw contact between the meter movement, the circuit board, and the instrument cluster will often reduce the errors. There are three screws that attach the meter movement to the circuit board and three screws that attach the circuit board to the instrument cluster.

There are two trim pots that can be adjusted to calibrate the tach. Generating signals for several different RPMs is required to make adjustments. I have a test setup that can generate signals for 500, 1000, 3000, and 5000 RPM.

I have had mixed results with adjusting the tach. The tach in my driver I did adjust yeast ago but it quickly drifted out of calibration. I have a spare tach that I adjusted six to eight years ago and it just tested really good.

I have been meaning to try and sort out the source of drift. I suspect the trim pots but one of the three electrolytic caps on the board is located in the calibration part of the circuit.

Mike
 
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