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Ignition Coil to Tachometer Connection!

anotero

Autocross Champion
Location
Hither and thither
Car(s)
Mk7 GTI
I got a sequential shift light that needs to be connected to an ignition coil. I am very bad with electrical components and have no idea how to connect the shift light to read the ignition coil signal to then translate it to a tachometer reading. All I know is that it needs to be connected to the negative coil terminal. How do I find the negative terminal? Do I need to splice any wires? How do I get to the negative coil terminal?
 

Finglonga

Drag Racing Champion
There is no single ignition coil, there is one on top of each spark plug. A single coil is a thing of the past, no car uses a single coil now they are like the golf or have a coil pack that is 4 separate coils (or more depending on engine) in one pack.
 

Hoon

Autocross Champion
Location
Rhode Island
Open the wiring harness above the coil on Cyl 1, the large brown wire is the tach signal wire for the dyno. My guess is it will work for a shift light also.
 

Golf7RR

Go Kart Newbie
Location
NE
I got a sequential shift light that needs to be connected to an ignition coil. I am very bad with electrical components and have no idea how to connect the shift light to read the ignition coil signal to then translate it to a tachometer reading. All I know is that it needs to be connected to the negative coil terminal. How do I find the negative terminal? Do I need to splice any wires? How do I get to the negative coil terminal?

I followed this from another user on cylinder#1 and purple/green wire and for the most part works. however when really getting on it while driving and above 5.5k rpms or so the lights think the rpm is higher than what the dash shows. it doesnt do this is you sit and rev. If you find a better wire to tap please let me know.
 

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anotero

Autocross Champion
Location
Hither and thither
Car(s)
Mk7 GTI
I followed this from another user on cylinder#1 and purple/green wire and for the most part works. however when really getting on it while driving and above 5.5k rpms or so the lights think the rpm is higher than what the dash shows. it doesnt do this is you sit and rev. If you find a better wire to tap please let me know.
What shift light do you use?
 

Golf7RR

Go Kart Newbie
Location
NE
Same. How much off is it from the dash tach reading?

Around 5.5krpms it was reading more like 6500 which is where i set it to stop and all lights to flash. but it doesn't occur when say you are in neutral and rev while parked. maybe there is some sort of interference since the wire i showed you to the actual unit it pretty long and it might "pick-up" electrical noise depending on how it is routed. i haven't actually scoped the line so i do not know how large the pulses are and/or how prone they are to noise..But for that theory to hold it should happen regardless of the car being parked and revving or getting on it while driving. well there are lot of settings and its new to me so i'll have to try to figure it out.
 

anotero

Autocross Champion
Location
Hither and thither
Car(s)
Mk7 GTI
Around 5.5krpms it was reading more like 6500 which is where i set it to stop and all lights to flash. but it doesn't occur when say you are in neutral and rev while parked. maybe there is some sort of interference since the wire i showed you to the actual unit it pretty long and it might "pick-up" electrical noise depending on how it is routed. i haven't actually scoped the line so i do not know how large the pulses are and/or how prone they are to noise..But for that theory to hold it should happen regardless of the car being parked and revving or getting on it while driving. well there are lot of settings and its new to me so i'll have to try to figure it out.
Interesting. I'll test it out too once I get it. How long did it take yours to arrive from Australia if that's where you bought yours?
 
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