Adjusting Electronic Speedometer
 

Someone mentioned in a previous post that they thought there was a potentiometer adjustment screw on the back of the electronic speedometers. Does anyone know if this is true and if so which way do you turn it to reduce or increase the speed that it reads? Thanks! I have a GPS which tells me my speedometer is overly optomistic about the speed I am travelling.

have not done it yet. adjustment tiny screw is in there. Was told to turn 1/8 turn and see what happens. http://www.pelicanparts.com/support/.../hotbounce.gif

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Don't know if this helps, Kurt, but I suspected that my speedo was off on '82 SC, tested it against mph/rpm in gears graph in back of owner's manual. Results surprised me: 65 indicated= 60 actual, but 80mph and 100mph were right on the money! Go figure. :confused:

The screw is inside the housing, so it is not something easy to adjust multiple times with trial and error. You could get the spec for your gear/tire combination from a known Porsche speedo shop and set it once. I ended up drilling a small access hole before reassembling the gauge that allowed me to adjust the setting through the housing with the smallest flathead screwdriver. I plugged the hole with RTV once I got the setting right.

Olivier

Oliver...do you remember if turning screw clockwise increases the speed reading??

I'm sorry, it has been a long time and I can't say I remember for sure. If I had to guess, I would say clockwise = higher indicated speed, but the memory is fuzzy. I actually only had to adjust it twice on the road before I got an almost perfect reading, judging by the .10 mile markers on the interstate.

I think I originally made a large movement in one direction or the other to confirm the direction before I went out for the final calibration.

Olivier

Guys,

Find someone with a portable GPS and put it in the dash and drive. It will tell you exactly what your speed is, and is more accurate than the cops radar. Then calibrate the speedo using the GPS and you will be dead on.

Lots of hunters, fishermen and campers have the portable units, work nice and cost $150 or so...

JA