My wagon, which doesn't get driven very often, has been displaying some gauge fatigue. The temp gauge is all over the place -- often at normal, then dropping off the scale as if the car were off. The tach has also recently died.

I pulled the cluster to finally do the temp comp board trick. While I was in there, I also checked for corrosion and all that good stuff and gave some of the contacts a good wire brushing. Everything looked good as far as a once-over goes. I put her back together but the tach still doesn't work. (Didn't have a chance to warm up the car and check the temp gauge).

I cleaned the contacts at the coil and checked the red and white wire inside at the contact for the tach and it gets 12 v when ign on and when I ran the engine, I was getting 750-1100 Hz on my meter, which is probably about right in rpm for where it should be idling. Anybody know if the pulse is modulated in any way?

Anything I'm missing? Is there a bad ground I should suspect on the cluster? The other gauges and lights work fine. The car has 307k mi on it, this cluster has only been out 4 or 5 times (once to replace the temp gauge). The tach was put in about 100k mi ago. Could just be that the tach's day has come. Hope not. TIA.