Yeah, good luck finding the low pressure fill valve.  I Looked for quite
some time and came up with nothing (although by only the greatest stretch of
imagination could you call me a mechanic) - I took it to a local reputable
service station and they said that I was stupid to try to fill it myself,
that if I over filled it or underfilled it, I could do more harm than good
and ruin my compressor.  I exclaimed that the filler bottle came with a
complimentary pressure guage (complete with a red, yellow, and green zone!),
to which they retorted that it was inaccurate and a sure way to screw my car
over.

Would someone please comment on this?

Thanks!

JD

The low pressure port is located on top of the accumulator. The accumulator
is located on the passenger side near the right front wheel well. Turn the
front wheels to the right to help with access. Look under the front right
bumper, you will see a polished aluminum cylinder looking thing (It has 2
aluminum hoses coming out of the top) That cylinder is the accumulator. It is
snugged up against the front of the wheel well cover(towards the bumper).
Slip your hand on top of the cylinder. You will feel the 2 metal hoses and a
cap. The cap is the dust cap to the low pressure port. Twist off the cap and
attach the quick connect hose and recharge. I would recommmed using some type
of measuring gauge to prevent over filling the system. Hope this helped. I
had to find it myself and it was a bit challaging at first. Ford was useless.