capacitor on tach wire
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=70675
Printed Date: July 14, 2025 at 2:03 PM
Topic: capacitor on tach wire
Posted By: amazingaudio
Subject: capacitor on tach wire
Date Posted: January 13, 2006 at 11:07 AM
Has anyone heard of putting a 250 micro farad capacitor inline for a tach wire. We have had trouble learning the tach on a 99 Grand Prix. We are using a scosche (compustar) unit and technical support said to do this. Has anyone else ever heard of doing this.
Replies:
Posted By: ryguy
Date Posted: January 13, 2006 at 11:30 AM
never heard of this been in the bis. 10 years . does it work ? ------------- MECP installer,technician
Posted By: Powermyster
Date Posted: January 13, 2006 at 12:20 PM
new to me also
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Why oh Why didn't i take the blue pill
Darren Power
Posted By: amazingaudio
Date Posted: January 13, 2006 at 12:31 PM
haven't tried it yet still trying to check if someone else has done it first
Posted By: JWorm
Date Posted: January 13, 2006 at 1:05 PM
I was told to do that a few years ago by a tech support person. Don't think it ever worked.
Are you using the white or PURPLE / white at the coil? If so, I would try using an injector wire.
Posted By: dualsport
Date Posted: January 13, 2006 at 2:31 PM
I suppose it might be intended to act as a filter for noise or block out any dc offset or something-
As long as it's connected in series and not in parallel, it couldn't hurt to try.
Posted By: Powermyster
Date Posted: January 14, 2006 at 1:44 PM
lol you try it and let us know
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Why oh Why didn't i take the blue pill
Darren Power
Posted By: dualsport
Date Posted: January 14, 2006 at 2:37 PM
Letcha know just as soon as I do- haw! 
Posted By: amazingaudio
Date Posted: January 14, 2006 at 5:12 PM
tried both wires mentioned and injector. Will let you know results after we try cap.
Posted By: snotdobbs
Date Posted: January 14, 2006 at 10:55 PM
click click click click click click boom! Did it work? what happened..... -------------
Posted By: amazingaudio
Date Posted: January 19, 2006 at 10:35 AM
car is coming in tomorrow will try cap and see what happens
Posted By: extreme1
Date Posted: January 19, 2006 at 11:04 AM
did you make sure the dip switch inside the brain is set for tach sense and not alternator sense?
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Shaughn Murley
Install Manager, Dealer Services
Visions Electronics
Red Deer, Alberta
Posted By: 5150azn
Date Posted: January 19, 2006 at 4:01 PM
Is the room filling with suspense or what?
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Tell the Snap-On guy I'm not here!
Posted By: Powermyster
Date Posted: January 19, 2006 at 4:15 PM
LOL i for one am keeping my eye on this topic
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Why oh Why didn't i take the blue pill
Darren Power
Posted By: amazingaudio
Date Posted: January 20, 2006 at 10:42 AM
10 9 8 7 6 5 4 3 2 1.............. Houston we have lift off. I was a little skeptical about this working but it sure did. Don't really know why it worked just know it did.
Posted By: dualsport
Date Posted: January 20, 2006 at 10:55 AM
I'm sure everyone will want more details...
Did you try it back to back, by shorting out the cap, and confirmed it stopped working again?
If you can, it'd be interesting if you can make a DC measurement on the signal before and after the cap, referenced to ground and see what it reads-
Posted By: Powermyster
Date Posted: January 20, 2006 at 11:27 AM
good to see it worked can you try what dual sport suggested
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Why oh Why didn't i take the blue pill
Darren Power
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