rxpclb

As I was driving home today, I looked down and suddenly the speedometer started vascilating between 60 & 80 mph when I was actually going about 45-50 mph. The tachometer seemed to be operating as normal. Later the speedometer went all the way down to 0-20 mph. The motor sounded the alright. Any idea what's going on? Do you think replacing the speedometer cluster would solve the problem?

georgeb944

There is a speedo sensor located on the front differential area of the transmission. It's more likely that the failure is there than in the gauge cluster. Probably cheaper, too.

georgeb944

Also, VCDS has an output test for Instrumentation that works the entire cluster, including the analog gauges (including speedometer).

rxpclb

Also, noticed the cruise control is not working. My mechanic is not familiar with the sensor you mentioned previously. Do you have a part # you can supply or link to more info on it? Tx

Check out this brief video of my problem & tell me what ya think.... BTW a Check Engine light came on today on the way home from church.

georgeb944

http://www.ecstuning.com/Audi-C5_A6-...ter/ES2143444/

4Driver4

Call me crazy, but I'd take a few minutes with VAG-COM to run some diagnostics before doing anything.

Prospeeder

Exactly, see what the instrument cluster is receiving for a speed signal, and what the engine computer is seeing also. If the speedo is all over the place but the signal is steady and correct the cluster is junk. If the signals all over the place like the reading bad sensor, or broken reluctor on the differential.

iamrph

Only one code came up: Vehicle Speed Sensor intermittent miss fire. The cold weather seems to affect it most. Today when it got up to 20 degrees I didn't notice any fluctuation. What would you do?

iamrph

Only one code came up: Vehicle Speed Sensor intermittent miss fire. The cold weather seems to affect it most. Today when it got up to 20 degrees I didn't notice any fluctuation. What would you do?

Prospeeder

Was that the engine computer codes? The instrument cluster received speed sensor input then sends another independent signal to the ECU about road speed. So thats not very conclusive you need to check the cluster codes and measure blocks using VAGcom or a high end scantool.