Speedo Issues

[kjm8888]

My wife's TGP has an odd problem; The OHD speedo is reading different than the in-dash speedo. The OHD speedo seems to be reading correctly but, at 65mph (on the OHD) the in-dash speedo was showing 80! After driving the car to work today, I think it has been modded by the previous owner. It definitely has more pick-up than my TGP, which is stock. It does have an aftermarket air cleaner on the turbo and a lower temp thermostat. I'm guessing it has a chip as well. I won't be able to get into it until Sat. morning. Any suggestions as to where to start? Thanks!

Kevin

[grinders_18]

Sorry I can't help you with this one, but on both TGP's I've owned I've had the same problem. Mine still does it. Whenever the dash gauge reads 38mph, I'm acutally doing 30mph...A recommendation: Make a small chart with what the speed in the dash reads versus what the Heads Up Display reads. I did that and still use it whenever it's too bright out to read the HUD. Just a thought! Good luck and I hope someone can recommend some help for us with this problem!

Krenzy

[mfewtrail]

Kevin, you're describing a VERY common issue with these cars. Something is faulty in the gauge clusters on this car that leads to this issue as well as others("check gauges" and "low coolant" lights stuck on all the time is the other issue these clusters have sometimes). A few people have sent out their clusters to have them repaired at electronics shops from what I remember, but they paid quite a bit for this service($250-300ish). Shawn Lin(the owner of the W-body board located @ www.w-body.com/forum. This is another good source of information for TGP's and other "w-body" cars by the way. ;)) fixed his TGP's speedometer issue by splicing in a resistor in on the cluster(he stated that he used a "1 or 10 megohm" resistor spliced across the "calibration resistor" on the gauge cluster. He could not remember which of those resistors he used, but he said that put his speedometer almost dead-on accurate w/ the heads up display afterwards.) I've been meaning to find some variable resistors(going to try to find variable ones so that I can simply turn the screw or knob on the resistor and drive the car again to see if the speedometer is getting any closer to accurate) around that range to try on my gauge cluster as it reads 8-10mph off cruising on the highway around 60-65mph, past that it gets worse. :icon_redface: I'm going to make a note to pickup some supplies at a local electronics store so I can go ahead and try to fix my cluster. I will take pictures and type out a write-up type article if this does work.

[Prospeeder]

Yea common problem, luckily mines dead on with the HUD still, just had the Check gauges light on constantly for no reason flickering. If you have that problem go to the w-body.com info page and look it up, its easy to do! Good luck

[mfewtrail]

I picked up some resistors and whatnot today, didn't find exactly what I was looking for though. I ended up having to buy fixed resistors as nobody in town carried anything that I could adjust in the range I mentioned above(1 - 10 megohms). I am going to attempt to jumper them in first without soldering so that I don't have to solder and then remove several different resistors until I find the one that gets my speedo the closes to being accurate.

[kjm8888]

Thanks for the heads up on the heads up! :laugh: I'm really interested in knowing if the resistor fix works. That sounds like something I can handle. I'm much better with electronics than engine work, but I'm learning. If worse comes to worse I'll just switch out clusters so my wife's car reads correctly.

Kevin

[meltboy11]

sorry to bring up a dead thread, but I was searchin cuz I was having the same problem in mine with the check gauges light, and also the speedo and HUD not matching up... from what I see, the HUD is accurate and the speedo is wrong?... I would hate to get a ticket cuz my speedo is off, cuz I really don't wanna pay to get that fixed...lol

[TGP Nick]

HUD is correct, the needle gauges are off.