I have an '89 Subaru GL10. Going for a casual drive. One moment with turbo then no turbo. The turbo light indicator doesn't come on. I'm a big time newby and know little about how the turbo works to determine if it's something electrical or the turbo unit itself. Don't know if it would help to read a manual as it's probably a little more technical than I am. Any thoughts as to differentiating what it might be?

Can you still "feel" the turbo?

IE: When you floor it, is the acceleration flat and then ramp up, or is it just flat?

 

It could simply be that the light is burnt out.

Or the sensor that turns the light on has bad conection, or is dead.

 

The turbo doesn't just "turn on" with the light, the boost sensor turns the light on when 1psi of boost is detected. Use the feel of the engine to determine if you are still making boost, or if there truely is a problem.