Tach Installation Tutorial

stangkid88

New Member
Nov 11, 2005
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Seattle area
I recently installed an Autometer tachometer in my car, thanks to the help of 66Runt and 19Stang66. I am a complete newb to electrical wiring, so if someone like me could put this together than I am sure anyone could. 66Runt recommended I make a thread with some of the pics I took because although there are lots of threads on this topic there is no definitive 'tach wiring' thread. so here goes

Step 1: buy a tach

I bought the pedestal mount 3 3/4" Autometer Street Tach in a black housing for only $81.88 from Summit Racing. I chose this because it is not too big and blends in nicely with the instrument cluster in my '65.

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Step 2: mount the tach

I chose to mount mine off to the side on the steering column. this part is up to you. you can do what I did, or mount on the dash, or close to the A-Pillar, or by the shifter, etc. In my position, the only thing I am blocking on the dash is the ALT idiot light, which will be useless anyway once my 1-wire PowerMaster goes in. If you are mounting on a flat surface, there are two screws included to hold the tach down. I used a hose/worm clamp (about $2.00) I got from Ace Hardware to secure it to the steering column.

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Step 3: Wiring!

your tach will come with 4 wires sticking out the back. Green, Red, Black, and White.

Green goes to either the (-) side of your coil or to an ignition box if you have one. note: always attach to the tach terminal on the ignition box instead of the coil, otherwise you will fry your tach! This is the only wire which goes into your engine bay, everything else is under the dash. The picture helps show where the wire goes through the firewall, it's above some wires and should be close to where your windshield wiper wire goes.

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now that you have the wire through the firewall, attach it to the coil/ignition box. for the coil, buy a loop connector to attach to the wire and bolt on. for the box, mine had a male post terminal sticking out of it. I bought a male terminal to attach to the wire. (pics below)

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Next up, it is probably a good idea to ground your tach. While the instructions from Autometer recommend grounding it to the engine, any unpainted bolt with contact to bare metal will work. The most conveniant I found was the interior courtesy light on the driver's side. Attach a loop style connector to the end of the wire and slip it between the screw and the light housing.

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Let's connect the red wire to the ignition. As per 66Runt (Scott) if you do not have soldering skills (me) then you can use bullet connectors which is on par with factory wiring. This part gets kind of confusing, but you'll figure it out! close to the courtesy light under the dash, you should find a short red wire with a green stripe coming from your ignition switch that connects to a pink wire. Disconnect these two. You will now want to make one of these:

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using these:

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these are bullet connectors. I bought a 6-pack from Ace Hardware of both male and female connectors, and this should be enough unless you start losing or breaking them like I did. In total, you will need 3 male and 2 female connectors. you will need a wire stripper/crimper for this part (about $8.99 for a cheap one). take about 2 inches of wire, stripping off about 1/4" inch of each off the end. Wrap these two wires together, and insert them into the back of the male connector. Then simply add the female counterparts to the other end of the 2 wires. If done right, you should end up with a 'Y' like above. now, crawl under that dash (don't strain yourself!) and attach the male connector to the female connector on the red wire coming from the ignition switch. The factory connectors are a little larger than the connectors I bought, so you may have to play around with a screwdriver/pliers/sharp edge to open them up a bit. Make sure there is good metal to metal contact, then you can wrap some electrical tape around the connection to secure them. Remember that pink wire? this plugs into one of the female connectors. Once again, you will probably have to open up the female connector a bit to accept the male bullet. Once you have that in, attach a male bullet to your red wire coming from the tach and attach that to the other leg of your 'Y'. Congrats, this is the hardest part!

So I know these pics kind of suck because they are blurry and I took them when I was all done so you can't see much, but I hope you can make some sense of them...

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Finally, your white wire is used to tap into the dash lighting. There is a factory harness with three female holes that you can use to tap into. You should be able to find this hanging around somewhere in the same area behind the dash. Simply attach a male bullet connector to your white wire (enlarged again) and connect. Unfortunately, I couldn't get a picture of the tach lighted up because of the flash in the camera, but here is the harness you are plugging into.

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Step 4: Test

First off, I would test the lighting. My tach came with light bulb covers so you have the option of keeping the white light, a red light, but I used a green cover to match the rest of my dash lighting. If your tach turns on, that means your white wire is connected well and you are grounded. Next, it's time to fire her up! Make sure your tach is correctly calibrated for your engine (clip wires on a 5" tach, set buttons on smaller tachs). If the car does not start (mine didn't the first time) go back and check through all connections, especially the Y. I actually remade a second Y and then it started for me. Although it is not the cleanest or most professional looking, I wrapped up the excess wiring in electrical tape and taped it to the top of the steering column as close as possible to the firewall. This way, you can't see it from the driver's seat and is only visible if you're looking from underneath.

Congratulations!! You've just gone from complete newb to an experienced electrician (or close to that...) I know probably nobody bothered to read through all this, but if you did, I thank you. It took me over an hour to do all this, but if it helps at least one person or is refered to in the future when tach questions come up, then it will be all worth it. So whether you think I am completely insane, did a good write up, or don't know what I'm talking about, a couple comments would be pretty cool to see if I'm actually worth something around here.

:SNSign: :SNSign:
 

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Nice job! But is there a rubber grommet where your green wire passes through the firewall? If not, the metal could rub through the insulation and short the wire out.
 
dawtips said:
Nice job! But is there a rubber grommet where your green wire passes through the firewall? If not, the metal could rub through the insulation and short the wire out.


Good write-up. I would also recommend a grommet for wire protection and keeping water, oil, fumes, etc. from entering the interior compartment (I know it's not a big hole...but every little bit helps).

Years ago...I did short my tack wire on firewall (mainly a ****ty job on my behalf). :nonono:
 
Very nice job.

I'll 3rd the gromet. I thought you would just poke a hole in the gromet for the washer wire. Kragen and Napa have a good selection.
Great pictures and an excellent write up!:nice:

Scott