Instrument cluster tach & Speedometer reading too high

I've a '97 Passat TDI. Unlike most posts here, the instrument cluster on this car is doing just the opposite. The speedometer reads much much higher than the actual speed of the car, and the tachometer bottoms out at the stop showing super high revs of the engine (basically moving full circle). The fuel gauge also acts up. All this while driving at a normal speed. I've cleaned the ground contacts under the battery but that hasn't helped. Any idea as to why these gauges over-react? Also, I've read a couple of different instructions on how to remove the cluster. What is the actual procedure for this 1997 model? I've got a 2 week window to fix this before I leave. Thanks

Did the cluster suddenly start doing this, or is this a replacement cluster, or has this cluster always done this?

It's the original, and it started doing this some time ago just out of the blue. Weather has been warm to hot all the time.

Remove the three leftmost dash vents, closing them first. Then remove the headlight switch and the OBD cover. Remove all the screws you uncovered. Put the steering wheel all the way down, and release the 3 tabs holding the OBD port in if you can. If not, the bezel surround will swing out of the way enough. Gently remove the bezel, which exposes the 2 screws holding the cluster in. If they're original, the heads will be covered in red paint. If not, then the cluster has been out before.

To remove the cluster:

Remove the 2 screws and rotate the cluster down and pull it out slightly so your hand will fit behind it. Press on the sides of the 2 connectors and pull them straight off the back. The cluster is now out of the car.

Sounds like it may be a bad ground or the cluster is fried. I'd the ground checks out, I'd contact Derek White at Chubs Auto (do a search here for the contact info). He's good and inexpensive. I have 2 clusters with him now and a 3rd to send out once those come back.

Good luck.

Thanks Abacus. That' ll be a big help. Why would I need to uncover the On Board Diagnostics (OBD) cover? Does it get in the way? I've bought a replacement used cluster that came from Europe, and it has only one connector on the back. The seller reassured me that it would fit this model year car. I wonder if the Canadian edition has only the one connector. I'm in Canada, btw. I won't know until I pull the cluster out of the car and at the moment it's in Mexico. I read an article here (http://www.tdiclub.com/articles/MFA-Conversion/) where modifications are made, and the poster stated that American Passat TDI's are different from Canadian ones in some aspects. I'm hoping it's the right cluster. I'll know soon enough.

northern pointer said:

Thanks Abacus. That' ll be a big help. Why would I need to uncover the On Board Diagnostics (OBD) cover? Does it get in the way? I've bought a replacement used cluster that came from Europe, and it has only one connector on the back. The seller reassured me that it would fit this model year car. I wonder if the Canadian edition has only the one connector. I'm in Canada, btw. I won't know until I pull the cluster out of the car and at the moment it's in Mexico. I read an article here (http://www.tdiclub.com/articles/MFA-Conversion/) where modifications are made, and the poster stated that American Passat TDI's are different from Canadian ones in some aspects. I'm hoping it's the right cluster. I'll know soon enough.

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I would not gamble on a euro cluster no matter how tempting it looked, there are too many dissimilarities between the US market and Euro market cars to make this work easily unless you absolutely know what you're buying and what it's from. Further, you really ought to get the cluster harness with it in order to run it properly.

If the back has only one connector I can already say that your harness will not work right.

I hope that it works for you but I'm not optimistic.

Steve

Thanks Steve. I've already bought the European cluster. It wasn't expensive...$57 Canadian including shipping so I took a chance, knowing full well it might not fit, because I have not been able to find one in North America. If it comes down to it, I'll take off the cluster from the car and bring it home to Canada, then ship it for repairs to someone in the States who people have recommended on this site. But like I said, apparently the American Passat is slightly different in its cluster than the Canadian one, so I'm hoping that with the car being Canadian, that it may fit. Fingers crossed.

But my question still remains: Why would the tachometer and speedometer read higher rpm's than they should, and the fuel gauge act up? Every post that I've read here with cluster problems has indicated just the opposite....hardly any movement, if any, at all. Weird!!!! Is my cluster the exception? If so, why?

Like was said above, I would check and clean the grounds first. Bad grounds can do some wacky stuff. The cluster might be fine.

northern pointer said:

But my question still remains: Why would the tachometer and speedometer read higher rpm's than they should, and the fuel gauge act up?

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Lots of different ways electronics can fail.

Did you check the orb of death to make sure it's not corroded and make sure it'd fully seated? There are also three grounds right next to it that can mess with cluster operation.

Check for loose or broken wires near the orb of death as sell. Also take out the battery tray and check for chaffed and exposed wires under there.

Yes, I've cleaned that orb of death to no avail and no loose or broken wires near it. All those connections are clean and tight. I'll check under the battery tray, thanks Lenard. Will also unbolt and clean the negative battery cable at the engine/chassis end if I can get at it. I'll be in Mexico this weekend so I will get on it there and see how it goes.

Cleaned the negative ground cable from the battery at the engine block and a few other grounds I could spot. Also jiggled the fuses at the fuse box for better contact. Resulted in both speedometer and tach needles changing their readings. Speedometer still reading too high but no longer bottoming out full circle. Tach still doing full circle, although at first try it was reading proper rpm at idle. As for removing the cluster, The headlight switch is under the single left side vent so I don't know how to get at the tab holding the switch in place. There doesn't appear to be a tab inside the vent outlet. How do I get the switch out without breaking it?

Push the headlight knob in hard, and then turn clockwise... it should rotate a bit more than usual (past "ON) and then click, which is the sound of the locking tabs releasing.

You should then be able to withdraw the headlight switch, wires still attached. The wiring then unplugs from the switch.

Thank you. Got the cluster out. The replacement from Europe has only one connector on the back. I took a chance getting as I didn't know if mine was one or two. So can't use it. Fortunately it didn't cost much. Sending mine to Derek at Chubs Auto. He said mine was a common problem. The chip that controls the step motors has died.