I note that the temperature gauge on my 1988 740 (b230ft) does not appear to be working. I have learned where the sensor is located, thanks to previous posts. It has 2 wires - a black/yellow and a yellow. Assuming I can get at the little bugger to pull the plug off of it, an I correct that I ground the solid yellow wire to check the gauge? If the gauge moves, the sender is bad. I see a lot of different brands of sensors are available. Are there any recommended brands? And if the gauge does not move, what then?