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Any of you guys ever see your CVI (VRef) voltage on your scangauge fluctuate? I just looked at mine today and it is steady 5.00v. Can't get it to move, hi idle, lo idle, koeo, doesn't matter. I'm thinking my x-gauge is not programmed right.
The Vref has to be very stable.That is easy and simple when dropping
from 12VDC to 5VDC. If you got enough ripple in the charging system
to effect the Vref you would have other things popping up.
Thanks. I know it needs to be stable, but I wasn't sure how stable it actually was. Mine just seems a little too stable. If it was reading 5.01 or 4.97, I would feel that it was a true reading. But 5.00 exactly? Ford Engineers aren't perfect and my 6.0 definitely isn't. I would expect some fluctuation, even it is caused by the scangauge, wiring connection, heat, actuators, etc.
5vdc is a common operating voltage for many silicon based electronics (computer chips). Even laptop and desktop computers have a 5vdc output from their power supply. Because the switches in the chips are so delicate they require steady, even power to avoid excessive heat and glitching. The various sensors on the truck also require a steady voltage supply so the return voltage doesn't vary. Vref can vary slightly from truck to truck but (just to back up Sean's post above ) being exactly on spec with no variation under any conditions is a good thing.
The 7805 voltage regulator (it's 5 V) only needs about 2 volts overhead.
So you have 7 VDC in with a max or 25 VDC. With the right sized cap on the
output you can be bouncing the in voltage from 7~25 and not see much if
anything at the output so long as your not over drawing it. That IC is really
old school. I am sure that even with discrete components you could do the
same. If you ever got near the cutoff voltage you would be dead on the road
well before that. 7 VDC will not run a 6.0L and that is where you would have to
be to see any ripple in the Vref.
I haver not set Vref on my SGII in some time. I'll load the Xgauge and see what I get.
I would be curious to see what others are showing.
If anyone is wondering, I was chasing a problem with my ICP and throwing codes 2286 and 2287 and wrench light accompanied with occasional surging and ICP defaulting to 875 psi. Changed ICP and pigtail with new IH parts and quick check of harness and problem remained, so I wanted to verify Vref. Digging deeper into the harness, under turbo, found this (see attached) not an easy find. Temp fixed now, but need a new harness soon.
) being exactly on spec with no variation under any conditions is a good thing.
