Gauge Cluster Issues/IVR

Check out post 15
Bench testing rally gauges

Use the photo to test the guages. Ohm meter between sender and 5v common posts should give 10 to 12 ohms for each guage. (Update, I measured my 70 guages again and got 11.6 and 14.4 I opened one of them and it was like new inside) you don't get that the guage is internally broken. O ohms = shorted, anything much higher than 12 ohms (from others it indicate it appears that 20ish would be a good Max) anything much over that would indicate a bad connection.

If you open up a guage you might get lucky and only needs a connection reattached. But if the heater wire is toast or the bimetal is toast I would be looking for a replacement.