VDO Speedometer

[ninexrep]

Hello out there. This is my first attempt at writing to Club Cobra and I definitely need help. I recently purchased a BDR roadster build # 1054. Brand spanking new. I love the car but the VDO speedometer is giving me a constant problem. I've tried to calibrate it according to the instructions in the BDR manual. The first time I did it the pulse number was 550, it reset but the speedometer never made a "full sweep" and worked for about a day. Then it started to fluctuate all over the dial again. So I went thru the instructions again. This time the pulse number came up 7330 and it reset to the mileage again, but still no full sweep at the end of the calibration process. Worked for a while then quit again. I then tried the setting with a known pulse it worked okay for about an hour then started either not registering at all or wildly fluctuating over the speedometer range. It has been driving me crazy. Can anybody out there tell me what I'm doing wrong? I don't have too much hair to begin with and I'm pulling out what little I do have. PLEASE HELP!