My guage has read what appears to me to be low for as long as I can remember and thought I'd investigate further and perhaps try a new sender.

The guage has three temps: [ 100 | 210 | 250 ] equaly spaced, 210 dead in the middle and a hash mark between each #. I always run a standard 195F TStat (changed a couple few times in the life of the car). So I'm pretty sure the water temp is running 195+ish.

The needle is always right on the hash mark HALFWAY between 100 and 210. This would approximate 155F.

Does the has represent 155? (note: guage is non-linear)

Is that normal or similar to your guage?

I've had some luck with other older GMs with factory guages to get them to read a little more accurate by locating a properly calibrated sender (suprisingly these were NOT GM/Delco service replacements) and replacing. I've found many replacement senders including GM's service replacements are not properly calibrated and this makes a big difference on guage accuracy. (my guage works properly - bottoming when disconnecting and pegging when grounded as it should)

The aftermarket replacements (Wells, Sorensen et al) seem to use spade connectors whereas my installed original has a round 'slide on' type connector. I can easliy modify the wire of course - just pointing out a difference.