Yo Don,
As Ron & Fred advised.
Following by Ford for a 96, but same for your 94:
Engine Does Not Reach Normal Operating Temperature @
http://www.diesel-dave.com/vehic/manual/stj/stj33013.htm#c
Damaged thermostat.
Cooling fan.
GO to Pinpoint Test C.
CHECK FOR FROZEN FAN CLUTCH
Perform fan clutch test as outlined in Component Tests.
Did fan clutch pass test?
Yes GO to C2.
No REPLACE fan clutch. REFER to Cooling Fan Blade and Fan Clutch in the Removal and Installation portion of this section. miesk5 note, this requires a specific type of Strobe Light & Tachometer. Our local radiator repair shop does this test. See test @
http://www.diesel-dave.com/vehic/manual/stj/stj33014.htm#fccmp330
C2 CHECK THERMOSTAT OPERATION
Remove water thermostat and check opening temperature as outlined in this section.
Does water thermostat begin to open and become fully open at temperatures in the specifications at the end of this section?
Yes REINSTALL water thermostat and CHECK temperature gauge operation as outlined in Section 13-01. @
http://www.diesel-dave.com/vehic/manual/stj/stjd1018.htm#extract_1379 miesk5 note, requires 74 ohm & 7.9 ohm resistor.
No REPLACE thermostat.
A simpler test is to; "...Pull the R/Wh wire straight off the sender & ground it to the block, intake, or head. Then turn the key to RUN. If the needle pegs, replace the sender. If not, diagnose the circuit. Also, read this caption: TSB 95-13-02 Erratic Temperature Sender - Factory temperature senders with a date code before 2774 are known to be defective. The code is stamped into the side of the hex. The format is the Julian date + the last digit of the year, so that's the 277th day of 1994. So 0085 is good; 1934 is bad; 3034 is good; 2765 is good; 3582 is bad. The sender should test at 74 Ohms cold; 9.7 Ohms hot. If you're having trouble with your temp gauge, try to read the date off the sender before any other diagnosis. A new sender from NAPA is under $10..." by Stephen miesk5 note, price ismost likely higher now.
Sender Location Diagram by Gacknar (The Mall-Crawler, Jeremy, "Big grey megga beast") @
http://web.archive.org/web/20130522155833/http://www.supermotors.net/getfile/265237/original/GT-40%20lower%20intake.JPG
Sender Installation Location pic in a 93
Source: by spivster (Joe S) @
http://www.supermotors.net/registry/6944/23369