I don't like those aftermarket wiring diagrams you find in Haynes, Mitchell, and other manuals.
They are confusing because they are always incomplete
(in this case there's no note about the wire you labeled A). That's why I scanned and posted PDFs of the 73-91 GM OEM diagrams.
I don't have 1981, 1982, or 1984 diagrams yet. However... If you download and look at the GM wiring diagrams for
1980 &
1983 there's no difference in the temp sender circuit #35.
In the engine compartment there is a single Dark Green wire Circuit #35A running from the bulkhead plug to the temp sender/switch. I don't know what the other green wire is but it's not for the temp gauge circuit.
With gauges there is a single #35B wire at the cab side of the bulkhead plug. According to the notes the only clusters that have the extra circuit #35A on the cab side are the base model idiot light clusters.
- Circuit #35B from the bulkhead plug (cab side) to the instrument cluster
- Circuit #35A, NOTES; [omitted with gauges (1980), Base Only (1983)], from the bulkhead plug (cab side) to ignition switch ground #1. If you are converting to gauges you'll need to remove this wire.