About a year ago I installed a B&M transmission temperature gauge for my AW4 on my '94 XJ. Now the gauge works intermittently. Actually rarely works and when it does, the needle vibrates back and forth. I don't know how to test to see if the gauge is faulty or the sending unit. Any thoughts?? Yes, I've checked all the connections including the ground.

 

I had the exact same problem with mine, and I was able to fix it be cleaning the connections from the sender and using one of those spikey star type washers for that nut on the sender post. Those type of washers give a real good connection, and B&Ms kit didn't come with one if I recall.