tach wires

[jakegday]

hey, i got a tach in the mail today and the instructions on it were useless, these r probably the shittiest instructions ive ever seen for anything, anyways, theres 4 wires on the back, red black green and yellow, i know black is ground and green is the signal from the engine, however i just wanted to double check with someone with a little more experience on the red and yellow wires, im assuming red is 12 volt constant and yellow is 12 volt ignition, can someone please tell me if this is right or not?

[ImSoYesterday]

Red is positive yellow/white should be baclight on tach

[Classicrocjunkie]

http://hp.autometer.com/instructions...nstruction.pdf

[jakegday]

the autometer instructions were useless as well, (the tach isnt an autometer, and i have no gray wire) but now im wondering if the red wire is a 12 volt constant, or 12 volt ignition, i was thinking about that and realized there was no need for a tach to have a 12 volt constant (like a car stereo) anyone with even just a thought please let me know thanks

[Classicrocjunkie]

What kind of tach is it? Remember you get what you pay for. Gimme a sec and i have some instructions somewhere on how to wire into the PCM.

[Classicrocjunkie]

Tachometer Installation for a 1998+ 2200 Engine


You Will Need:
12V Test Probe
Wire Cutter
Wire Stripper
Extra 12-16 Gauge Wire
Wire Connector Butts
Wire Loom or Sleeve Hose
Electrical Tape
4Amp or 5Amp Fuse
Cartridge Fuse
Metric Wrench





READ INSTRUCTIONS CAREFULLY

Look for a desirable place to mount your TACH and mount it. NOTE: Be careful not to drill a whole on a week spot, and make sure that none of the TACH parts is leaning on the windshield.


Using a wire loom and electrical tape, neatly tuck the TACH wires on the side of the dash going down to the foot pedals.


After mounting the TACH, remove the cover on the fuse box and the outer side dash cover. Also, open the fuse box. Clip the 12V test probe to a good ground connection. Don't use the door or the body of the vehicle, instead, there's a good ground connection under the hood, close to the windshield wiper motor.


THERE ARE FOUR WIRING CONNECTIONS THAT WE HAVE TO DETERMINE.
White Wire - 12V Dash Lighting (+)
Red Wire - 12V Ignition Switch (+)
Black Wire - Good Negative Source (-)
Green Wire - TACH Terminal from the PCM


First: WHITE WIRE - 12V Dash Lighting

To determine a 12V dash lighting, turn the headlight switch on, and using your 12V test probe, test some empty slots on the fuse box. If you've found a slot that turns your test probe light on, turn the headlight switch off and test that slot again. If the test probe light is off, then you've found your 12V Dash Lighting connection. You will need to unscrew the fuse box to be able to work on easier. Using the wire stripper and cutter, cut and connect the WHITE WIRE from your TACH to the 12V dash lighting that you've found. Make the connection neat, clean, and accurate by using a connector butt.


Second: Red Wire - 12V Ignition Switch

To determine a 12V ignition switch, turn the ignition on, (but don't crank the engine) and using your 12V test probe, test some empty slots on the fuse box. If you've found a slot that turns your test probe light on, turn the ignition switch off and test that slot again. If the test probe light is off, then you've found your 12V Ignition Source connection. This time, you will need to use a 4Amp or 5Amp fuse to make the connection.
Cut and strip the wires properly and connect the Fuse Cartridge along with the 12V ignition source you've found and the RED WIRE from your TACH. Do not install the fuse until you are ready to calibrate the TACH. Use connector butts to connect the wires properly and neatly. Install the fuse box into its place. Install the Fuse Cartridge to an accessible area, where you can change and install the fuse (the right side of the fuse box is a good spot). Install the two parts of the dash. Using an extra (2-3M) 12-16 gauge wires, strip and connect the BLACK and GREEN wires to extend the length. Neatly tuck the wires underneath the dash and find the firewall or the hole where wires are directed to the engine compartment. Then run the BLACK and GREEN wires through the firewall into the engine bay.


THIRD: Black Wire - Good Negative Source

If you can connect it directly to the Negative source of the battery, it would be great. If you can't, then there's a good negative source right beside the A/C blower or fan - it's one of the major source of ground - you can't miss it. It is connected to the body of the vehicle. Connect the Black Wire from your TACH to the negative source, making sure that the wire is not excessively long.


FOURTH: Green Wire - TACH Terminal from the PCM

Locate the PCM (Refer to a shop manual for location). There are two slots of connections for the PCM. The upper part (which is BLUE) and the lower part (which is BLACK). Using a wrench, unbolt the lower part (BLACK), making sure not to damage the gasket. Remove the light blue face for easy access to the wires. Locate PIN #10, it is WHITE WIRE. Remove some of the electrical tapes for more access to the wire.
Cut, strip, and connect the white wire to the Green Wire from the TACH. Use a connector butt to properly connect the wires. Tuck neatly all excess wires using wire looms and electrical tape.


Now you're ready to Calibrate your TACH. Follow the instructions that came with the TACH on how to calibrate it.

[jakegday]

lol, you automatically know what year and engine i have, the brand of the tach is TIMEX, like the watch, i know you get what you pay for, and in this case, i didnt get very much, im just gonna assume my yellow wire is equal to the white wire in the instructions, and also, thank you very much, once again youve been a great help, see ya