Rpm gauges

I have just fitted rpm gauges

I have just fitted rpm gauges to a coil tubing unit power pack and cabin but both are showing idle at 1500 rpm how do you calibrate these back down anyone know

"If you could upload a picture

"If you could upload a picture, that would certainly help. I don't know what a "coil tubing unit power pack and cabin" is....."

"(v92) im guessing you

"(v92) im guessing you must have the tach cable attached on your blower drive starplate directly. if so it needs a 2:1 right angle adapter.its hard to find and leaks oil and allways breaks (made of alum. not good for the gulf) but, it is better to scrap that and put a blank starplate in its place. if there is nothing driven on your camshaft knock a remote tach adaptor in the butt of your cam then put a remote mount coverplate then you could tie your tach cable directly to the plate.its the best and most common and if its on a coil tubbing unit it makes money so its easily paid for."