One morning, my speedo didn't register at all. After in town driving for 10-15 minutes I got out on the interstate doing 70-75 mph (used tach) for about 15 minutes and it suddenly popped up to the correct speed reading and worked fine: rock steady at all speeds even when I came to a stop. When I came out 2 hours later it still worked fine.
-I didn't drive it for a week and the same thing happened. Didn't work, highway, worked the rest of the day (even after stopping for a few hours).
-About 3 days later I cleaned the magnets and the sensor as suggested in another thread. After cleaning, I drove it and I had the same problem: pop up and work perfectly after 15 minutes on the interstate.
-Two days after that I got in it and it worked fine from the get-go.
-Two more days later: no reading.
I drove it 35-55 MPH for 35 minutes. No joy. Parked it for 2 hours and then took it onto the interstate. 15 minutes later it pops up and works fine! I'm seeing a pattern so after getting it to work, I park it and immediately jack it up and put a meter on the wires in the tunnel. Continuity goes from 1 to almost 0 eight times per revolution. The sensor seems to be working fine.
What do I try next? I really don't want to buy a sensor if I don't need one (especially when some folks have had problems with the replacements and they had to buy 2-3 to get one to work).