I know what you are talking about. You have to have the fan off. Im pretty sure it reads like sound pulses, but when the fan to interior of the car is on it messes up the readings. The 1/4 mile times are off because it doesn't include the pitch yet we dont drag race and haven't gone out and calculated everything. We use it to see Gs on the track which works great.

 

no mine is just the opposite when the fan is ON everything is a-ok, but when it is off everything goes haywire. g-tech is supposed to be accurate with in 5,000's of a second, and me and this fellow are the only 2 that seem to be having trouble (or that i've ever heard of). my guess is since we both live in fl and they come with a window mount-... sun prolly fried it. i know i read somewhere on the g-tech site that it measures off of 9-15v. so another possibility is that the battery is toast (which mine is showing some signs such as dim lights at idle). mine is hard wired and has the 1 amp fuse in line, it's also grounded straight to the battery, but everything is getting worse stats.

7.54 for 0-60, 15.88 for 1/4, 100hp, 102tq- that's stock but depending on how accurate it was that day... back then the #'s were pretty consistant.

 

man, i sure as hell wouldnt be able to have this in my car long. it would prob say my car runs a 16.. then i would have to do the same thing thats gonna happen with my autometer gauge.. involves a hammer, a video camera, and a concrete wall..

 

ok i'm gonna take back that one statement about buying a new battery-...why you ask? because i did, good ol' optima red top $193 later. gtech slightly further off. before i had to have the blower on. now it's the blower, headlights, radar detector, pretty much everything else. so my next guess is gtech is getting too much power but not enough to blow the fuse. i think my next attempt to curing my gtech issue will be either calling g-tech and obliterating them with questions, or rewiring to cig lighter harness, possibly trying a voltage stabilizer.

if anyone has any clues please let me know!