finding the 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=123690
Printed Date: May 02, 2025 at 6:57 PM
Topic: finding the tach wire
Posted By: skywatcher2001
Subject: finding the tach wire
Date Posted: September 27, 2010 at 9:42 PM
I have a 1999 Chevy Siverado 1500, V8 (4.8L)
I installed a Viper 5701 alarm. Can I tap into the TACH WIRE at the dashboard gauges or must I get it off the PCM?
-------------
Pass on what you have learned - Yoda
Replies:
Posted By: howie ll
Date Posted: September 28, 2010 at 1:03 AM
Test. The right wire should be tested with a DMM set to AC volts, you should get a reading of 1.5-3.5 VAC at idle increasing slightly when you rev up.
-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.
Posted By: skywatcher2001
Date Posted: September 28, 2010 at 9:39 PM
yes, I did I believe the tach wire was (is) the problem. The tach wire at the Dashboard Gauge isn't dedicated to just tach. It also supplies other gauges too (abs, fuel, brake, etc).
So I need to go to the PCM. Any idea which pin (wire color) it is??
-------------
Pass on what you have learned - Yoda
Posted By: howie ll
Date Posted: September 29, 2010 at 2:54 AM
If you have lots of wires going in you're wrong, the wire you described is the IGNITION feed to the guages. If you have a plastic flexible printed circuit board on the rear of the instrument panel there will be 3 terminals behind the rev counter (tachometer).
1 = 12volt ignition.
2 = Ground.
3 = Tach.
Test.
-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.
Posted By: howie ll
Date Posted: September 29, 2010 at 2:55 AM
Sorry I meant to add that if it is a flexible printed circuit board there will be lots of tracks visible, trace the tracks back to a connector.
-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.
Posted By: skywatcher2001
Date Posted: September 29, 2010 at 11:46 AM
What I did is cut that wire (white) and the tach went to zero so I figured I had the right one. After I connected the Viper 5701 (and DLPKGM) into the tach the ABS LIGHT, BATTERY and FUEL LIGHTS came on (fuel gauge also registered zero).
I like your idea...to trace the lead on the circuit board. I'll try that.
-------------
Pass on what you have learned - Yoda
Posted By: kreg357
Date Posted: September 29, 2010 at 12:00 PM
The Viper should sync up to a cylinder Ignition Coil just fine. Might be easier to run the wire into the engine compartment.
-------------
Soldering is fun!
Posted By: skywatcher2001
Date Posted: September 29, 2010 at 12:02 PM
I did run a wire into the engine compartment. I'm just trying to find the tach wire.
-------------
Pass on what you have learned - Yoda
Posted By: kreg357
Date Posted: September 29, 2010 at 1:02 PM
A Tach signal can be found at ignition coils and fuel injectors. As Howard pointed out, a Digital Multi Meter is necessary to verify the correct wire. All connections in the engine compartment should be soldered.
-------------
Soldering is fun!
Posted By: skywatcher2001
Date Posted: September 29, 2010 at 1:12 PM
Thanks Kreg,
Im going for the injectors (easy to reach and find). I will solder when finished. thanks for your help.
-------------
Pass on what you have learned - Yoda
|