Carpokes Porsche Forum

I have a 1999 996 C4 with the original gauge cluster . All of the gauge faces are bubbling . So I ordered some replacement gauge face decals . To date I haven't installed them yet .

Last year I also purchased a used gauge cluster from a similar year car that has perfect gauge faces . My chassis has 150k and the used cluster has I think about 120k . If I install the used cluster will it display the mileage that is in memory in the cluster ? Or will it display the mileage in the memory of the ECM ? If it displays the lower mileage how can I correct that ?

I think I will attempt to replace the gauge face decals first on the original cluster . But I would like to have a backup plan just in case . Lots can go wrong with 26 year old plastic . Any advice is appreciated . And just to be clear , I am NOT trying to alter the odometer to flip the car . This 996 is my baby and I just want the odometer to be accurate if I decide to use the other gauge cluster .

My understanding is that the miles are stored in the cluster. The odometer on a brand new cluster from Porsche can be adjusted upward with PIWIS, but only within the first 100 kilometers. After that, there is no official way to adjust it. The idea is that Porsche can put a new gauge in and match the existing miles, but not change the miles otherwise. However, some speedometer shops have cracked the code, and will do it for you if you sign their scary forms:

http://www.paspeedo.com/agreement.pdf

I don't know exactly how Palo Alto Speedometer does it. If they've isolated the non-volatile memory where the miles are stored, they may have a way to erase, reprogram, or replace those memory locations. That would be the professional, elegant way to do it. As a two-bit hack, if I had to do it myself, I'd figure out how to replicate the speedometer signal and then set the gauge to 100mph until you reach the desired mileage. Not sure if the 996 odometer will roll over to 0 when it hits its limit, however, so that hack might only work to add miles. Although there are easier ways to change the old mechanical odometers, you can see my hack in action at the 2:30 mark of this video. I added maybe 50k to that odometer when testing our 3D printed odometer gear. Only took a few days at 100+ mph.