Well I installed my boost gauge the other day, and the pos used 3 power cables. I wired them all into the tac fuse because it was late and I was tired . I'm planning on taking 1 wire and splicing the 3 power cables into it. I also want to install an oil temp gauge which will use a similar amount of cabling. For simplicity sale I want to also wire that into the dash fuse. I guess I'm asking, how much can I tap into the fuse before its too much?

 

What?

Why not do it the "proper way" and use an add-a-fuse at the passenger compartment fuse panel?

This way you're not cutting up the wiring harness on the car in case you want to undo it

 

You should be fine. To check you need to measure the amount of current being drawn with everything on that fuse active. Then see how much the max draw of the combined gauges will be. Add the current draw without gauges to what the gauges will draw. If it is less than the max rating of the fuse you are good to go.

 

Could also use a fuse tap at the fuse box, wire your gauges in sequence as well and save yourself and your wiring harness from making multiple splices.