PhDMDRX7

My odometer just stopped working, I read through the archives and some peole have had success replacing the back light (not me, it worked but I replaced it anyway). Others said the whole speedometer needs to be replaced. I did that, I had an extra with 187,000 miles on it. I put it in the guage cluster and plugged it in and YES it worked. I then put the guage cluster back in the cowling and back in the car and guess what? Odometer doesn't work! Any ideas? I've done nothing to the car from the time the original odometer was working until now.