tach wire issue, '06 super duty diesel

Hi all, Ive searched for a while and just got more unsure of the correct tach wire. Im working on an '06 super duty diesel. Alot of posts here say to use the GREEN/ wht above brake release. I used a dmm and im showing 12v in the ignition on position. And 14 with engine running. I thought I read on here that I needed 1 to 8 volts. So Im wondering if this is the correct wire. Then I thought I read you test it in ac voltage. Is that my problem? If I test it in ac will I get the 1 to 8 instead of the 12 to 14 in dc? Ill try that tomorrow. If not whats the next best place to grab a tach signal? Ive also read I may not need a tach wire. Thanks in advance!!!!

Test in the AC volts range.

This additional info from Bulldog Security :

On DIESEL Engines the TACH wire is a LIGHT GREEN / WHITE wire in a

5-Pin Harness held up with WHITE tape located behind the Parking

Brake Release.

Test it as Howard mentioned.  If your DMM isn't auto ranging, set to 20V AC.

 

Soldering is fun!

Thanks for the reply guys. Ive been a mechanic for 32 years and although Ive only done a few alarm systems and one other remote start, this is the first time Ive ever set my dmm to ac when working on a vehicle. Thanks again! Ill test it this morning and put this in the learn something new every day file.

that tach signal at the parking brake harness sometimes works and sometimes doesn't. if you want to be sure/safe just order a 454t tach generator.A DMM is a beautiful thing.

MECP Advanced Installer Certified.