My Car is finally running again after swapping out the Duke for a 2.8.
I also swapped out the old tachometer and added the GT one, but it's getting very little movement. When I start the car, it moves about a quarter inch, but does not change with the engine idle. I checked my tach filter and have continuity there. Is there a test I can run directly on the tach itself? Can I apply current to the contacts and see if it moves, or will that blow something? I still have the old one, and will put it back in to test things if necessary. I know I can convert the old one to work with the 2.8 as a last resort, but my preference is to use the GT tach, as I also have a set of center cluster guages here to use as well.
I can't see starting a new thread for a very similar question so if you don't mind I'll just add to your question...
If one has a working tach but doesn't believe it's accurate is there a way to check that? I get the same reading via WinALDL as is displayed on the guage but I get the feeling that reading is also faulty. Maybe it's just me but it seems that when it's revved to 2K RPM it sounds like she's ready to blow up I know our cars are loud but the slow tach movement along with the rapid accelerator pressure just doesn't seem right.
Sorry if this seems like a hijack but my intentions are entirely otherwise. Searching the forums is hit or miss so I thought by adding to your question it'd help out down the road. Don't hesitate to speak up if you see otherwise and I'll edit it out.
-Tim
[This message has been edited by Damien (edited 03-29-2007).]
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12:18 AM
KurtAKX Member
Posts: 4008 From: West Bloomfield, MI Registered: Feb 2002
I don't know about an exact testing procedure, but you could always buy a little 2 5/16 autometer tach from autozone and hook it up to the "tach" lead of the coil and double check against that....
Good luck
Kurt
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12:33 AM
paulmckibben Member
Posts: 332 From: Atlanta, GA, USA Registered: Nov 2001
Apply less than one volt AC from a 60 Hertz source to the unplugged wiring of rhe speedometer sensor. (I used a 3 volt "wall wart" transformer with a potentiometer to drop the voltage to less than 1 volt.) Turn the ignition key to ON (don't start the engine) and the speedometer should read 54 MPH.
I use my laptop PC and ToneGen software, which will generate a crystal-based "laboratory accurate" test signal. ToneGen is available as a free download for "for demonstration and testing purposes," and it's not that expensive to purchase.
Using 60 Hz AC as a test signal works fairly well, but an accurate variable frequency tone generator allows you to check tachometer or speedometer calibration throughout its full range. The conversion formulas are really simple (Hz is the tone frequency in pulses/cycles per second):
Marvin, that is a great idea. I just d/l'd that program. just be sure you keep your volume down, as it will put out up to 5v on the headphone line. just remember the tach for a 6 will read 1/3 of the set frequency.
for those that use the wallwart transformer tho, don;t fret, the 60 hz signal in the US is accurate enough for that use. it is regulated to .01 % I think it was, but you can get some minor variances localy due to loads and transformers and such, but not more than 1% usually, more than accurate enough to set a tach.
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10:36 AM
Marvin McInnis Member
Posts: 11599 From: ~ Kansas City, USA Registered: Apr 2002
just be sure you keep your volume down, as it will put out up to 5v on the headphone line.
Good advice. What I usually do is start with the volume all the way down and slowly increase it until I get a stable indication on the tach or speedo, then increase it a little more (~50% to 100% higher voltage if you're measuring it).
quote
the tach for a 6 will read 1/3 of the set frequency.
Careful there!!! Your statement is correct only if the frequency is stated in cycles per minute, while tone/pulse frequencies are conventionally expressed in cycles per second (Hz). I have added relevant conversion formulas for Hz vs. RPM/MPH/KPH to my original post.
[This message has been edited by Marvin McInnis (edited 03-29-2007).]
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10:46 AM
Mar 30th, 2007
Eclipse Member
Posts: 2040 From: Woodstock, Ontario Canada Registered: Jun 2004
Thanks guys. I will try this. The other method I thought about is building a controller similar to the gun that we use with slot car tracks, that I can use to control the voltage. Thoughts?
no good on the gun, the tach is a frequency meter, changing the voltage won;t work.
Marvin, I think I inhaled too much fiberglass resin and acetone, you're right, I should be careful what I post when I'm tired and sore. (stupid boat....)
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07:44 PM
Eclipse Member
Posts: 2040 From: Woodstock, Ontario Canada Registered: Jun 2004
I know our cars are loud but the slow tach movement along with the rapid accelerator pressure just doesn't seem right.
