DA51

I switched clusters a couple of months ago. The new cluster has 98,000 miles and came from the same year and model-1992 SC400.
It has nice needles. I replaced all the cluster bulbs before installing it.
I took a trip last month and noticed when I hit hard expansion joints the Temp needle went to Hot. I've taken the cluster out of the dash still attached to the harnesses. With the engine running, I tap the side of the cluster and the needle goes up, then tap again and it goes back to normal. Is this a bad Temp Gauge?
I've got my original cluster and can install the Temp gauge and switch needles, does this sound OK?
I was reading a previous post that the Temp Sensor wire is in the center harness plug, is that correct? Something about 330 Ohm resister?
Any help or suggestions will be appreciated.
Thanks.