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Tachometer Dilemma
So, let's see who can assist me here, I purchased a very nice OEM Tachometer to replace the current aftermarket Steward Warner tachometer. I was told the OEM tach was in good working condition and
I paid $500 for it, we installed the tach and we could not get it to work, appears that is not receiving the signaI. I sent the tachometer to a local repair shop and I was charged $295 to "Fix it" I also took my SW tach and they put it on the bench and is working properly on the bench and on the car. I was told by the shop that because I'm running a Haltech that I won't be able to run this tachometer because of the signal? ( ignition system) I then send the tach yet to another shop, Palo Alto Speedomer, I was told that indeed the tach is on need of repairs ( moving meter and service the circuit board) and the cost will be $395 but the up shift light will not work, however, they are not sure if this tach will work, again because of the Haltech and signal, if I pay for the repairs and the tach still doesn't work, I will need to send it back to replace the circuit board and again they are not sure if this thing will work. So I could potentially invest $700 and the thing may still don't work. Any suggestions? Who is my Tachometer guru in the house? Just in case is a Haltech Elite 2000
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10.76@139-1/4 mile 0-1 mile 193MPH I Love to Shine Cars 
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08-14-2022, 06:02 PM
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Location: Charlottesville Va
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Juan-Haltech's tech faq on tach drive : https://support.haltech.com/portal/en/kb/articles/tachometer
I don't speak Haltech, but it must be doable-here's a car TRE built with a Haltech 3.4 and what looks like a stock tach-maybe reach out to them and they can help? Porsche 911 ST Tribute in Fraise — RETROMOD
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Greg Lepore 85 Targa 05 Ducati 749s (wrecked, stupidly) 2000 K1200rs (gone, due to above) 05 ST3s (unfinished business) |
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08-15-2022, 05:52 AM
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10.76@139-1/4 mile 0-1 mile 193MPH I Love to Shine Cars
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08-15-2022, 06:33 AM
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FYI My factory tach works great driven from my microsquirt. The biggest issue is getting the # pulses correct. My memory is a little hazy, but earlier CDI units put out different # pulses per revolution than later ones.
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'86 no-sunroof 930 coupe: Emissions removed, FrankenCIS controlling eWUR, lambda, COP ignition. Tial f46P 1.0 bar spring, SC cams, K-27/29, lightweight clutch, TK Longneck intercooler, RarlyL8 headers and dual-outlet hooligan '14 Jaguar XK-R: Bullet proof windscreen, rotating number plates (valid all European countries), martini mixer, whatever you do don't press this red button! |
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08-15-2022, 09:14 AM
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John Bell Jbell959 is a regular contributor here and a gauge guru. I’d think he could sort you out.
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81 Pacific Blue 930 Euro coupe slicktop on a strict diet, Rarlyl8 headers, Blowzilla turbo, Tial waste gate, Full bay I/C, Home made center out exhaust, Leask WUR, MSD 6AL, PLX wideband Wevo shifter, LSD. Next up, Cams, Heads and port work |
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08-16-2022, 09:13 AM
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Palo Alto had consulted me a few weeks back about this problem as they use my driver board to do some of their repairs. I believe the issue is the stock board in the tach is not providing a pull-up resistor that the Haltech needs to see to toggle it's output. I told them my driver board would likely solve the problem because it incorporates a pull-up. You can do a simple test with your setup... on the tach signal attach a 2.2K 1/4W resistor. The other end of the resistor to +12V. See if this fixes the problem.
The background of this comes from the Haltech support site: “The tachometer function provides a duty signal output to drive a tachometer. To generate a voltage signal, the output from the Elite must have a pull up resistor connected between the output and the required voltage for the signal. DPO-1 already has an adjustable pull up resistor on board and is the suggested output to use for this function, and makes installation a simpler process. What is not known is how your Haltech is programmed and whether the DPO-1 output is being used to drive your tach. https://support.haltech.com/portal/en/kb/articles/tachometer |
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08-16-2022, 09:55 AM
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@BobAshlock Small World! Thank you so much for providing me that information. We are going to look over the settings on the ECU again.
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10.76@139-1/4 mile 0-1 mile 193MPH I Love to Shine Cars
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08-16-2022, 06:29 PM
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08-16-2022, 06:30 PM
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Glad John can help. He is the "go-to guy" on tachs and other instruments.
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08-17-2022, 09:50 AM
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Yes, Bob Ashlock is the guru! He has provided necessary boards to successfully repair 2 factory tachs that I was able to do myself. I hate soldering small circuit boards. Maybe I'll send to John for the next one. I love what John is doing making custom tachs!
I also bought Bobs tach tester which is invaluable for testing and then calibrating these tachs. I learned that most factory tachs read a little high at higher rpm. Jaun, Please report back because I just ordered a Haltech 750 for a single plug 930 project.
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08-25-2022, 09:23 AM
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10.76@139-1/4 mile 0-1 mile 193MPH I Love to Shine Cars
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08-25-2022, 01:18 PM
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1988 Porsche Carrera 3.2 Turbo
