my turn signals work but the indicator on the dash does not

You will have to remove the cluster and run circuit and bulb tests.

If all the outside turns signals work, that is, the bulbs light and flash properly, but the dash indicators either don't light up or they light but remain on, you likely have a dead relay. It's pretty simple. Of course, as your truck is twenty years old, it is remotely possible that the indicator bulbs both burned out at the same time.