I have my MEVI installed and everything works fine when I activate it manually with a toggle switch.

I'm now ready to install the RPM swith. I originally was going to put it under the hood and tap into the #1 coil.

After reading many posts on this, I've decided I like Dave B's (and other's) idea of putting it in the fuse panel where it's protected from the elements and easily accessed.

My question is, where do you tap into the ECU to get the Tach signal?

'95 SE, automagic.

Dave B - You out there this morning?

 

when i was installing my nitrous kit.. i had the very same question.. so i searched and then found a thread that told me exactly what color wire was the RPM wire coming from the ECU.. then i tapped it and ran it back to the engine

 

I remember the post you're talking about. At the time it wasn't information that I needed so I didn't keep track of it. I spent several hours last night reading through posts and couldn't find it. I'll search again maybe I'll see it this time...

 

Another option is to tap the coil and run the wire into the cabin to abvoid messing with the ECU.

I have my RPM switch in the cabin and I can mount it above the steering wheel for test runs.
Dave

 

Pull the plastic cover off the ECU harness, its the RED & YELLOW wire. that goes to Coil #1. this is where i grabbed my RPM source for the VI.

word of caution--the space inside that plastic cover is TINY and you wont be able to use a wire tap, you will have to strip the wire back and solder your wire coming off the harlan in there.

i wish i had the wiring diagram for the ECU harness, but maybe you can search and see if you can find it. its in the upper middle left of the harness--RED & YELLOW. (Coil #1)

 

Paul is right. It's a RED/YELLOW wire on the upper middle left of the harness bundle. I ended up using a crimp connector to tap into the wiring. I may end up going back and tapping into the coil pack just for insurance against a possible power surge that could possibly fry the ECU (could expensive with the JWT ECU). Make sure to use fusable links on the MAP sensor 12V supply, RPM switch 12V supply, and line leading to the RPM signal wire if you're going to the ECU.

I really suggest getting a Chilton's manual for $15. It's a life saver for the price and they give you the wiring diagrams. You'll really learn a lot about your car.


Dave

 

I was able to fit a wire tap

Too bad on '99s you can't pull from the ECU without killing the tach needle

I ended up pulling the rpm signal from the coil and running the wire inside the cabin so the Harlans would be protected from the elements.
-hype

 

I have a 97 and tapped into the #1 coil signal out wire at the ECU. I seem to recall the service manual calling it terminal #5. Have had no problems with this setup ever since I got rid of the relay. Works like a charm!

 

Thanks for the input guys - you've all been great help.