Typically you remove the finish panel around the intrument cluster,
then remove the screws holding the cluster in place.  Now look at the
back side of the cluster for screws or studs coming out directly
behind the area of the temp gauge.  *If* the gauge is mounted this
way, then it is highly likely that those screws or studs serve double
duty as electrical connections.  If you don't see this arrangement,
start carefully dismantling the cluster until you can locate the
attaching screws for the gauge.  Take pictures along the way, be neat
and careful.

Toyota MDT in MO

When I run a jumper from SIG to GND, the temp gauge needle jumps from
COLD to HOT. So, I guess the temp gauge isn't broken. Maybe the wire from
the temp sending unit to the temp gauge is bad.

Gary

From what I have seen and read it covers years 1987 through at least
2000 and involves most of the domestic Ford vehicles both cars and
trucks up to the F-350 and includes diesels. The "sending unit" is a
switch that just makes the "gauge" pop up to a reading somewhere in the
normal area on the dial as soon as the oil pump generates at least 3-5
pound of pressure. 97 and up started using a chip with the resistor in
it to operate the gauge. The only way around that one is to replace the
gauge with a true mechanical.

For a new sender these are parts that will work with the current wiring.
Auto Tune: PT3077B
Standard Motor Products: PS-60
Echlin: OP6091
Motorcraft: SW-1547-B, or E4ZZ-9278-A

You still need to find the 20 ohm resistor which can be in the sender,
inline from the sender OR behind the gauge cluster or in the case of
vehicles from late 96 through 2000 it is IN the chip on the cluster. The
only way out on those later vehicles is to replace the gauge itself.

More info  http://www.asashop.org/autoinc/march98/techtips.htm

And from the f150 forum

The oil gauge on the Explorer isn't. Simply put, the indicator on the
dash looks like a gauge, but it is really only a binary indication as to
whether the pressure sensor believes that the engine has sufficient oil
pressure or not. If it thinks there is sufficient pressure, then the
gauge reads in the "Normal" zone, usually pointing to a single place
(without varying based on temperature, RPMs, etc.). If there is not
sufficient pressure, then the gauge reads "low." The first item below
describes how to convert the "indicator" back into a gauge. Discussion
on this topic follows:

I went ahead and installed the transducer today. It was a universal 1/4
pipe threaded sender with the "slip over threaded rod" style of
electrical connection to the top. Plenty of room for the tee, original
switch, and the new transducer. I removed the switch from the 45 degree
long- shafted adapter. Used the end of the tee (not the center port) to
the adapter, mounted the transducer upward and the switch outward
(center port of tee). Was able to plug the original connector into the
new transducer.

The gauge read just left of the N in Normal prior to disabling the 20
ohm resistor on the dash cluster. After shorting out the resistor, the
gauge needle points to the A in Normal at 2000 rpm and around the O in
Normal at a warm idle in gear. The needle is heavily dampened (so to
react to changes) but is still a worthwhile modification.

I would say that the dash cluster removal is rather involved and not for
the faint of heart. In fact, living without the resistor modification is
really acceptable when you consider the gauge is dampened. If my wife
would allow it, in retrospect, I'd have just done the tee and added the
chime to the factory gauge but installed a real 270 degree mechanical
gauge. And not touch the dash.

And now! What the manual says about the OIL PRESSURE GAUGE!

"When the engine oil pressure is normal, the oil pressure switch is
closed (short circuit), allowing current flow through the 20-ohm
resistor on the cluster flexible circuit into the gauge which drives the
pointer to a position slightly above midscale. The switch opens (open
circuit) when oil pressure drops to a critically low level (4.5 - 7.5
psi) causing movement of the pointer to or below the "L" band."

"NOTE: The pointer of the magnetic gauge will remain in it's last
position when the ignition is turned off. It will move to the correct
(or actual) indication whenever the ignition is turned back on."