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Join Date: Aug 2013
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RPM switch wiring
I bought an Autometer rpm switch to run a shift light on my ‘82. Can I piggy back the leads of the unit off the corresponding tach terminals? Anyone have experience with this unit?
Thanks! https://www.summitracing.com/parts/atm-5312?seid=srese1&gclid=EAIaIQobChMIhKfN07rz_wIVwPzjBx03xQ6EEAQYASAB EgJrgPD_BwE  Sent from my iPhone using Tapatalk
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1987 Marine Blue 930 1982 911SC White Plains, NY Last edited by OldSpool87; 07-04-2023 at 04:16 AM.. |
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07-03-2023, 01:30 PM
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Bump for advice/insight. Thanks!
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07-05-2023, 02:04 PM
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Anyone out there with an aftermarket shift light? Most threads only relate to stick shift light in tach which I don’t have. Thanks!
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07-08-2023, 08:17 AM
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Racer
Join Date: Oct 2010
Location: Franklin, TN
Posts: 5,885
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When I ran an RPM switch (hour meter) in my race car I was using an MSD setup. I had no issues tapping into the RPM wire going to my tach from the MSD unit.
I don't see why it would a problem to do this with the Factory setup.
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Scott Winders PCA GT3 #3 2021 & 2022 PCA GT3 National Champion 2021 & 2022 PCA West Coast Series GT3 Champion |
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07-08-2023, 08:40 AM
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Thanks Scott. I run an MSD as well. I see a lot of threads on fussy tach signals and didn’t want to mess it up. I’ll give it a go. After all, what can be done, can be undone (most of the time).
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07-08-2023, 09:09 AM
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Got the switch installed and it activates the light. What’s odd is that at idle when the tach reads appx 900 RPM the switch sees appx 630 RPM. The switch is getting its signal from the white/red tach signal output on the back of the tach. This is the one which is connected to black/violet “tach in” with a double spade connector. I’m curious why it’s not seeing the same signal. Ignition is MSD Street Fire. No other issues. My plan is to confirm RPM with my timing light to make sure my tach is indeed idling at 900 RPM. Any thought out there on this RPM signal loss from white/red wire?
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07-11-2023, 06:39 AM
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Join Date: Oct 2005
Location: Northern California
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I have been using single and twin MSD 6ALs for about 20 years. I use that tach out signal to drive my tach, data acq/ system, and an rpm switch for an hour meter. Also an RPM window switch to operte a 993 intake flapper. No issues.
Sounds like you are using an available tach output instead of the MSD signal for your RPM switch. If so this might not be the same signal going into the tach.
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Mike PCA Golden Gate Region Porsche Racing Club #4 BMWCCA NASA Last edited by Mahler9th; 07-11-2023 at 08:37 AM.. |
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07-11-2023, 08:34 AM
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