MK2 1.8t instrument cluster issues...

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hey everyone, i am sure this has been covered some where on here, but i have exhausted the search and google. Any help would be greatly appreciated. But I have a wolfsburg 90 jetta running a 1.8t AWM, currently with a 16v gear box, with factory mk2 cluster, and stand alone(ems stinger). Now the issue is i cant get the speedo or tach working. I have everything else operational in the cluster, the coolant level indicator, battery light, oil pressure light inop due to no switches(running gauge), temp gauge and fuel gauge, but no matter what i do the tach wont come on, nor the speedo. I have tried the msd tach converter which didn't work. The ecu carries 2 different outputs for a tach one from an external ignitor and the other is an aux output. neither of which do anything. The ems requires a 12v power source tapped into the tach signal and a resistor inline to turn the ecu digital signal into the analog, which didn't work either. The speedo cable is good, but then still wont operate the speedo even if its out of the trans and being operated with an air drill. So I feel like i have to be missing a power or a ground somewhere to this cluster. The voltage regulator is carrying the correct voltage. Oh and the tach needle will jump when the key is switched off, which makes me think the tach is getting power. This is all i have left before i start street tuning, kind of need those gauges. Thanks for any help you guys can give in advance.

[Prof315]

The tach in a Mk2 cluster requires a much higher voltage to trigger because it was designed to be hooked up to the single coil negative that the factory motors have. You'll need some kind of tach adapter to make it work right or else a later model cluster or aftermarket tach.

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Well sh!t... I was afraid of that. Now to find out why my msd tach adapter doesn't get the tach going... thanks for the info

[MikkiJayne]

. The speedo cable is good, but then still wont operate the speedo even if its out of the trans and being operated with an air drill. So I feel like i have to be missing a power or a ground somewhere to this cluster.

The speedo is purely mechanical. Are you sure the cable is fully engaged on the back of the cluster? It can be a right PITA when the cluster is in place and sometimes takes a lot of fiddling to get it to seat properly. If its definitely in properly and the cable is good then the speedo mechanism must be dead.

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so the speedo now works. All due to the speedo gear bracket bolt to the trans being too long. It was keeping the gear from riding in its seat inside the transmission. Now if I can get the tach to work it would be golden. I was trying to run it off the external coil ignitor. Which actually should run the tach, it carries a high voltage output with a ground trigger. But I cant find in the Bentley if the tach is actually triggered by the ground or not. Anyone know which way that triggers? Of course the MSD tach converter should be able to run the tach with no issues...but it wont. One strange happening today with the tach was that it would jump up to 3000 while cranking with a jump box on the battery. Once the car started the tach dropped to 0 and just sat there. Anyone ever have anything like this happen with a swap mk2 tach?

[Prof315]

so the speedo now works. All due to the speedo gear bracket bolt to the trans being too long. It was keeping the gear from riding in its seat inside the transmission. Now if I can get the tach to work it would be golden. I was trying to run it off the external coil ignitor. Which actually should run the tach, it carries a high voltage output with a ground trigger. But I cant find in the Bentley if the tach is actually triggered by the ground or not. Anyone know which way that triggers? Of course the MSD tach converter should be able to run the tach with no issues...but it wont. One strange happening today with the tach was that it would jump up to 3000 while cranking with a jump box on the battery. Once the car started the tach dropped to 0 and just sat there. Anyone ever have anything like this happen with a swap mk2 tach?

The tach in a MK2 cluster operates on the VERY high voltage spike (300-1500V) created when the coil discharges. This spike is commonly known as a flyback spike and occurs any time you pulse the ground on a coil of wire. Injectors, ISVs, purge solenoids all create flyback voltage but a single coil ignition creates the biggest spike.

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Well Prof, thanks for that info. Didn't realize it was that high of voltage. I am thinking i will just do an aftermarket tach and call it good. Thanks again.

[Prof315]

Well Prof, thanks for that info. Didn't realize it was that high of voltage. I am thinking i will just do an aftermarket tach and call it good. Thanks again.

no problem that'll be the easiest way to go.

[Vegeta Gti]

if you do an aftermarket tach, you can do what i did and get one that fits in the smaller boost gauge size(2"5/8) and have it go to 8k. if not, you can wire in the MSD Tach Adapter 8920.

best palce to pull tach signal is from the orange connector, pin 9 i think..can't remember exactly. this willw ork for either, but with the aftermarket tach you don't need the tach adapter.

i used an autometer z series tach. works awesome. color matches my green dash...but i will change it to either white or blue to match boost,etc,etc.

speedo you can get a cable made if you go to a real trans like an 02J. but you should be running the stock cable currently. do you have a VSS patch in your software? deletes,etc?

[Ultraflux3]

I had a similar problem but the MSD 8920 worked for me. My standalone provides the newer style low current signal. I ran that signal into the 8920 which is basically an amplifier, I then took the output and ran it to pin G1/12 in the fuse box. It was that easy I had a working tach.

One thing I had a problem with it getting a good ground connection on the cluster, but if your other gauges are working you probably don't have that problem

[2OVT]

was just about to put my 8920 in and I saw the VSS patch comment, Vegeta. Can you explain what that is?

I'm using t10x(orange connector) pin 2 (T121/81 | red/green wire.)for tach single.

[BARELY LEGAL]

was just about to put my 8920 in and I saw the VSS patch comment, Vegeta. Can you explain what that is?

I'm using t10x(orange connector) pin 2 (T121/81 | red/green wire.)for tach single.

You won't need a VSS patch when running standalone. It's only necessary when swapping a car, using the factory ECU, and running a cable operated speedo. The ECU likes to see a speed signal.