EXT. temp guage ?

[Acezwild88]

just really quick i have a greddy ext temp guage im not shure how old it is but when im driving normal it reads fine around 600 or 700 but then if my turbo engages the guage dropes down to like 100 or 200 and somtimes dropes all the way to 0 is the guage going bad or is there something wierd going on with my car?

 

[turbolover2]

Most likely the sensor is no good. But it could be the gauge itself. I would try changing the sensor first though.