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Tach or Voltage

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=52799
Printed Date: March 28, 2024 at 6:55 PM


Topic: Tach or Voltage

Posted By: Gadgetfreak
Subject: Tach or Voltage
Date Posted: March 29, 2005 at 12:57 PM

Which is the better choice.   I have coil pacs and I am a little worried about finding the correct wire.   Is voltage as good as the other choices? 



Replies:

Posted By: jaurora
Date Posted: March 29, 2005 at 1:26 PM
Tach signals are usally better than voltage sense. But voltage sense is only good when adjusted properly. I have seen people use voltage sense and it takes a couple of times to start. It has a lot to do with outside  temperature. What is the year and model of this vehicle.

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MECP certified (If it really means anything)
Jeremy




Posted By: Gadgetfreak
Date Posted: March 29, 2005 at 1:43 PM
2002 Dodge Ram 1500 with the Commando 870 alarm.    Just a little nervous tapping into a coil pac.  The manual says to tap the (-) side but the test to find it says to ground out the black lead on the the meter and use the red lead to find the wire.   If the meter is set this way wouldn't the wire found be (+)?




Posted By: jaurora
Date Posted: March 29, 2005 at 1:51 PM

Use this wire. Let me know how you make out. Here is a tip when metering for the tach wire.

1) Set your volt meter to AC voltage.

2) Connect the black lead to a good ground.

3) Probe the suspect wire. Check you meter, you should read a low voltage (usally 0-5VAC) The voltage will increase as the rpms of the engine increase.

Tach  Signal:

 

TAN/RED

AT IGNITION COIL



-------------
MECP certified (If it really means anything)
Jeremy




Posted By: Gadgetfreak
Date Posted: March 29, 2005 at 1:55 PM
Thanks, I will let you know how it goes.




Posted By: Gadgetfreak
Date Posted: April 04, 2005 at 6:44 AM
That was the wire, remote start works like a charm.    Thanks for your help.   Posting another question today.   Thread topic is active arming.  If you can help here it would be greatly appreciated...




Posted By: Bob86zz4
Date Posted: April 06, 2005 at 3:34 PM
Jeremy,  you know a lot about car wiring I think.  I'm trying to install an Autopage RS-720LCD starter/alarm.  I have the wiring diagram showing the tach signal is pin 26 on the green connector of the pcm.  I have the 6.0 engine so it's purple.  I found the wire and it looks to be the correct one.  I wired it up to the alarm tach signal wire.  I can't seem to program the alarm/starter to learn the rpm signal according to the directions.  I checked the wire with my volt meter set to ac and only see about .01v.  Any ideas for another location to pick up the tach signal?  Thanks.




Posted By: Satkunas
Date Posted: April 06, 2005 at 4:29 PM
You can always grab a tach signal from one of the injectors. For safety sake, fuse the connection at .5A so 'if' the wire shorts somewhere you wont wreck the injector.

To find the right wire have a look at two or more the injectors. One wire color will be the same with all of them (high side), you want to connect to the wire that is a different color than the rest.




Posted By: Bob86zz4
Date Posted: April 07, 2005 at 3:27 PM
Thanks, Satkunas.  I will do that then.  For now I just programmed it to use the voltage check method and set it for a 1.2 second crank time.  Seems to work fine.  This is on a GMC Savana full size conversion van.  It's rather difficult to get the dog-house off the engine to get to the injectors.  And you can't get there going through the hood.  So, when/if I take the dog-house  off I'll hook the wire to the injector like you said to.  I still have that tach signal wire connected to the pcm so I'll just leave it that way and when time comes I'll cut it loose from there and solder it to an injector wire.





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