CGT h2o/fuel gauges too low, after voltage stabilizer

[Ken]

Hello,

On my '86 Coupe GT, the water temp and fuel gauges read too low.  I have replaced the voltage stabilizer/regulator with an untested new one sourced from a list vendor.  It did not fix the problem.

What is the next level of troubleshooting I can perform to fix this?  Do the gauges themselves fail in some other way?

I'm sure I'm supposed to test the new voltage regulator, which means I need to buy some test equipment.

Any tips are appreciated.

Later,

Ken