What does the sensor look like?
1984 should be a 1/4 disconnect with a single Packard 56 female connector like the sensor on the far right in the picture.
If you have the 01513321 nailhead sender, second from the left in the picture, it's the wrong one for your 1984 temp gauge. This sender takes a Female Packard 56 terminal but the plastic shell has a slot to slide over the narrow part of the nail head.
The Pico 5665PT repair pigtail with the slotted shell will fit both types of sender...
The correct connector for your 1984 sender would be a 2977253 Female Packard 56 single...
Both connectors have this Packard 56 Female terminal inside...
__________________
1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8
RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...
Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.