Whew! it's been a long week. 1.7 RRs, Mopar intake manifold, powertrax locker and some other goodies. I'm stuck trying to figure out where to connect into the tach wire for my N2O window switch. I googled, checked the manual and searched here. just must not be my day.

 

Cool sounds like you got your truck running nice. I got the powertrax too. I love it! The tach wire will probably be the feed from the distributer to the tach guage. Find that wire. Check the stickys at the top of this section for the service manual that has wiring diagrams in it.

 

thanks. I have the 2800 page manual set, and it doesn't have "tachometer" in any wiring diagrams. it mentions that its run by the Jxxx module, which also controls turn signals and headlights and such. it's very vague. I googled, searched this forum and spend an hour over the manuals with a friend. i really thought this would be an easy one.

thanks for replying.

 

EDIT: decided to paste it. how useless is this?
Tachometer (if equipped). Driven through J1850 circuits.

the Instrument Cluster transmits a message via J1850
informing the the FCM. The FCM will then turn off
the headlamps, park lamps and fog lamps.

The front control module controls power to some of these vehicle systems electrical and
electromechanical loads based on inputs received from hard wired switch inputs and data received on
the PCI bus circuit (J1850).

it also apparently runs the thermometer/compass and a ton of other stuff. not one mention in wiring though. argh.

 

the CTM is my guess. Seems to run everything else... LOL

 

That J1850 is the SAE term for the communications bus. The signal that operates the tach is not on a separate circuit, but is part of the bus communication between all the modules in the vehicle. I think you would have to have a MSD or similar ignition box to run a tach or window switch.


I had a random after-post thought...you might could use the negative side of the coil for a tach signal. I know thats how I did it on my fox body.

 

As long as there's a distributr and not Coil-on-pack, this works. The old HEI on our dually pulled tach from there.