Hello everybody!
I am having some trouble wiring an aftermarket tach I just bought for my truck, I have gone through quite a few different threads without finding a solid answer so I am posting a new one.
I have a 2005 F150 XL 4.2L Automatic with no tach on the gauge cluster (obviously). Yesterday I bought an Equus tachometer from O'Reilly for $35, the black is grounded to chassis, red is going to PCM power fuse, and white is going to gauge illumination fuse. The gauge gets power and illumination works. The problem is where/how do I hook up the tach wire. I tried splicing into the dark green wire on the first harness knuckle (closest to fender) of the PCM under the hood, passenger side. This did give me a signal but it was way too low. It read around 100rpm at idle and when I revved it to 2500rpm (using service mode on the dash to get that number) it would read around 200-300rpm ish.

Do I need to use a different wire? Tach adapter? Inductive pickup?

Thanks for any help.

 

You need to call the tach manufacturer for assistance.

 

With trucks with no tach, It is a lot easier to use a tach with inductive pickup. That brand sells them. I had one awhile back and just looked it up a few weeks ago for a friend. They are more expensive but no headache. It is power, ground, and a wire with a clamp. The clamp goes over number 1 spark plug wire. I used it on my 04 heritage no problem. Also sold it to a friend with a 01 hyundai accent and no issues. To be honest, not sure about how to install with coil packs. But I have heard about many issues with trying to find the right place to wire that in. If you get either one to work. Use your digital tach in your truck.

 

The 4.2 has spark plug wires, so an inductive pickup will work.

 

Here is a other post about install like yours. Hope it helps.
https://www.f150online.com/forums/ap...ding-tach.html

Also a link to a video I made on how to use your digital tach. You can use it to verify the rpms on the aftermarket one.
http://www.google.com/url?sa=t&sourc...UFV5uFNMuOQmfg

 

Oh yeah he already said it was a 4.2... i read it but it didn't register lol.

 

If you are able to return that tach, look at a Scangauge. It will tell you rpms, voltage, temp, a ton of stuff including trims if you like. It's real simple to install, just plug into the PCM port under the dash. Then program the items you want it to display which will include instant fuel mileage so you can learn how drive for better fuel mileage. Yeah, it's more money but you'll get more bang for the buck not to mention it's also a code scanner. Anything your PCM reads, it reads, all you have to do is pick what you want it to display. There's also the Ultra Gauge which is considerably cheaper. Does the same thing but it is Chinese made and best of luck with any warranty.
http://www.scangauge.com/
http://www.ultra-gauge.com/ultragauge/

 

Also OP welcome! Noticed it was your first post. I've had an 04 heritage 4.2L and just traded my 08 4.2L. Loved them both.

 

I bought one of the scangauge 2s. They are great. It will read intake temp, coolant temp, mpgs both instant and average, MAP, open/closed loop, hp estimate, tach, speedo, ect.... only thing it doesn't read on the 4.2 out of its functions is fuel pressure. You can have it display 4 things at once. For anyone out there that has a vehicle with cylinder deactivation, it won't read mpgs correctly and there is no update for it either. But you can take it from vehicle to vehicle and just change the engine size before going. If you want to take it from one vehicle to another, it's easier to buy a second cord. Btw price is around $180 but you can use it in any vehicle you own. Like I said cylinder deactivation is the kryptonite for the readings of mpgs but the other functions work. Also on my ram (has cylinder deactivation) the hp estimate was reading weird. My f150 had no issues with the functions.

 

I agree. Send it back and get a scanguage II. It'll do so much more for you. I don't even feel comfortable driving a vehicle without one anymore.

 

Lol that's almost paranoia. A lot of vehicles read 1/4 of what the scangauge does. My ram reads coolant temp, oil temp, trans temp, instant and average mpgs, oil percentage remaining, and the also the normal analog gauges. The 2015 subaru forester I rented had a couple more things I think but I can't remember what they were.

 

In addition to being to read more functions, you won't have some ridiculous looking tach bolted to the dash like some ricer Honda Civic!

 

^ that's what that tach looked like in my 04 lol. Scangauge is 10x better and 2 to 3x the price but you have like 20 things that it reads.