I recently installed a Zex wet kit along with a Zex window switch in my 2000 GT. I tested it on a 75 shot and had it set to spray from 3000 to 5800 rpms and everything seemed okay. I only sprayed it a few times to make sure it was working so I never really gave it a shake down run. I took it in for a dyno tune a few days later and did one pull on the 75 shot and everything went fine. We installed the 100hp jets and when the spray starts the window switch would begin showing erratic numbers on the display causing the spray to cut in and out. I have gone throught the wiring and tried several coils and injectors to get the rpm signal from but nothing helps. The window switch display will show an accurate rpm reading until it starts spraying nitrous, then it starts wigging out. Has anyone had any issues getting these to work?

 

Do you have a relatively full bottle which is maintaining proper pressure (~800-900 psi) while your making the pull? If yes then possibly plug gap is too large or other spark related issue. The window switch doesn't know or care what jets you are running it's monitoring & reporting the RPM's that its given. Since it works fine at the 75 shot the box and wiring should be fine. To confirm just bypass the switch and run it again.

 

I probably should have left the part about it running with a 75 shot out because I agree, I dont think it has anything to do with it. I was more trying to give a time line I guess. The issue was intermitent at first but now it is non-stop. I disconnected the window switch and ran it without and it ran great. I reconnected the window switch, checked all my connections and also tried another rpm signal source (this time coil #1) and it was just as bad as before. I could tell it wasnt going to work before I even let it spray because just cruising around with the window switch armed the rpms on the display would bounce around if you goosed it even a little. Under normal driving conditions the rpms were accurate. Fortunately the shop I got it from is willing to replace with another unit.