My 360 speedometer went limp :-(

I drove my 2001 360 F1 spider yesterday and noticed that the speedometer would occassionally twitch. For example, on the highway it momentarily would dip 20mph (70 to 50) and bounce back up. Happened both when accelerating and when cruising. There was no notable loss of power, and no other symptoms. Car has been driven every few days, including track time last weekend.

Today, leaving my neighborhood (lower speeds) it happened again and then went completely dead. At the same time, the F1 warning indicator went nuts (beeped multiple times and flashed, then stayed on solid). Also, the "ASR" indication came on as though the ASR had been turned off. Flipping the ASR switch made no difference. There were no other issues. Car shifted fine and drove fine. Downshifted correctly on its own when I slowed down. Rest of the dash was fine (including the TAC).

My working assumption is that the ASR and F1 indications are secondary symptoms because the systems don't know the car speed anymore, so the root problem is likely tied to the speedometer circuit. Does this sound reasonable?

I did some searches this morning but didn't hit on anything that seemed related. I plan to spend some quality time with the parts book this weekend to check the sender and connections. Was wondering however if anyone else has seen this issue.


Lou